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Suspension & Steering

  Experience in a Book
Suspension & Steering

 

GREASE (ZERK) FITTINGS: Unlike the newer American "low-maintenance" cars, the Jag has zerk fittings all over the suspension. Periodically it should be gone over with the grease gun, but please be conservative. It is tempting to grease fittings too often and to pump too much grease, which will destroy the seals or gaiters on the joint.

The following is a list of the grease fittings on the car:

  • All six universal joints -- good luck getting at the forward one on the drive shaft. The protective covers on the rear axle U-joints have openings for greasing, but they may not line up. You can relocate them as necessary.
  • All four corners of the flat plate under the differential (lower swingarm inner joints). There are holes in the plate for access to the zerk fittings.
  • The needle bearings in the lower pivot joint of the rear hub carriers; the fittings are just inside the rear wheels at the bottom.
  • Both front hubs. The fitting is on the side of the hub near the outer cap. With some wheel designs, the wheels do not need to be removed. Rumor has it these fittings have been deleted in later cars.
  • Both upper front ball joints -- remove the front wheels for access.
  • Both lower front ball joints. The fittings point inward, underneath the car.
  • Steering rack -- see the note below.

Also, the rear wheel bearings should be greased by removing the small cap on the hub carrier and spooning a little grease into the hole. Don't overgrease, because the excess merely spins out and coats the inside of your wheels.

The pre-1983 Jaguars also had zerk fittings on the tie rod ends, but the later cars were fitted with "improved" tie rod ends with no such fittings.

The ball joint zerk fittings are designed with a relief system to prevent the grease gun from applying too much pressure. Under the fitting itself is a plastic washer that covers the relief hole. When the joint is full of grease, any additional greasing will force the plastic washer to bend, allowing the grease to come out adjacent to the fitting itself.

Michael Neal sends this tip on lubricating the lower ball joint: "If the grease comes out from behind the plastic washer as soon as you apply it then the passage is plugged. The best way to clean the passage is to remove the lower plate and zerk fitting. Ream out the passage and apply some grease to the cup before reassembling. The grease in the passage hardens after a relatively short amount of time and plugs the passage."

When installing the zerk fittings on these ball joints, note that overtightening the fitting onto the plastic washer will deform the washer and open the relief hole.

See the note on lubricating the water pump.

Don't overlook the zerk fittings themselves as a possible source of trouble. Each zerk fitting has a tiny spring-loaded ball check valve to allow grease in but not out. It is susceptible to corrosion and jamming. They are also easily damaged by impact.

 

RIDE HEIGHT: XJ-S owners are often concerned about whether the car is actually supposed to sit that low, or if something is wrong. The Jaguar XJ-S Repair Operation Manual describes a check, but it assumes you have original tires with full tread. It also assumes you have "slip plates", devices you set the front tires on so they can slide around and not bind the suspension travel. The following is a derived procedure that subtracts the tire rolling diameter out of the equation in order to determine if your car is sitting at the "correct" ride height for the tires you have on it, and all it requires is a level section of concrete.

Position the car on level ground with nobody in it, no heavy stuff inside or in the trunk, a full tank of gas, the emergency brake off and the shifter in N. Push the car back and forth a few feet. When pushing rearwards, push on the front bumper and deliberately bounce the front of the car a little while pushing. When pushing forwards, push the rear bumper and deliberately bounce that end as well. This is to make sure the car is fully settled in its position.

Measure the height to the center of the front wheels. With any luck, they should be the same, but if they vary slightly determine the average.

Subtract 6-3/8" from this height. This gives you the correct height above the ground for the flat bottom of the cross member between the front wheels.

Using the same front wheel center measurement (do not measure the height of the center of the rear wheels), subtract 4-7/8". This will give you the correct height above the ground for the edges of the plate between the rear wheels with a full tank of gas.

So much for the "correct" ride height. Now, to describe what you actually have, a story from B. J. Kroppe: "My former supervisor (a Jaguar employee) did vehicle packaging for the F-Type. He started with XJ-S drawings and came across some things which didn't add up. So he went to the assembly plant and measured some XJ-S vehicles and compared them to the drawings. He discovered that the cars being produced (this was mid-late 1980's) were very much lower than the drawings said they should be.

"After some investigating he learned that over the years more features had been put on the car, making it heavier, but springs had not been changed to accommodate for the added weight, thus causing the lower ride height in the actual cars vs. what the drawings were saying."

In practice, it appears the XJ-S may ride about a half inch lower than the "correct" ride height, even when new. If yours is significantly lower than that, however, it's probable that either the shocks or the springs need replacing.

 

SAGGING FRONT END: If your Jag seems to be riding low on the nose end, a likely culprit to check is the front shock absorbers. The XJ-S uses gas shocks, in which the damping fluid is held under pressure by a small amount of gas within the chamber. A side effect is that the pressure causes the shock to try to extend. This extending force helps raise the car a little, especially when the suspension is soft. The Jag was designed for these shocks, and if they lose pressure, the nose sags. Since the pressure may be lost while the fluid is still present, the low nose may be the first sign of failing shocks. Of course, the rear shocks are also gas type and may cause the same problem, but it doesn't seem to happen as often.

 

SHOCK ABSORBERS: To check the front shocks, jack up the car and remove the front wheel. From inside the engine compartment, remove the locknut, nut, rubber doughnut and seat from the top of the shock absorber. Then reach into the wheel well, grab the top portion of the shock and pull it downward. If it is in good shape, it should move downward smoothly with a hiss, and when released should move smoothly but forcefully back to its full extended position by itself. If the motion is not smooth, or the shock compresses easily and quickly with no damping effect, or fails to extend itself when released, replace the shocks.

The traditional tests of shock absorbers involving pushing the car down and noting its recovery or noting the car's reactions over bumps are not entirely applicable to modern gas shocks. If a gas shock loses its gas charge, it may still appear to pass these tests; if it still has fluid in it, it will still provide some damping. The damping effectiveness is greatly reduced, however, and will get much worse over a series of bumps. And, as noted above, the car's ride height will be affected. There seems to be no substitute for disconnecting the shocks and checking them by hand. Checking the rear shocks will require a spring compressor to remove the springs from the shocks.

The front shocks should be checked before having the car aligned. The front end of the car sitting lower than it should has an effect on the camber, and will alter alignment settings.

The mail-order catalogs seem to offer only original shocks or big-bucks performance shocks. However, NAPA, Monroe, and Gabriel offer serviceable, reasonably-priced gas shocks for the XJ-S. Gunnar Helliesen says, "I bought Monroe Gas-Matics for my '86 SIII XJ6 and am very pleased with them." Nick Johannessen provides the Monroe part numbers:

Front: 4302
Rear: 43013

Matthias Fouquet-Lapar points out that Bilstein is now online: http://www.bilstein.com/shockframe.html "There is lots of tech info."

 

 

Front Suspension

 

CLUNKS -- FRONT: If something in the front goes "clunk" when you drive over a bump, check the rubber bushings on the top of the front shock absorbers. British non-metallics again. Any generic rubber shock bushing will do, and will do better than the original. David Littlefield says, "Generic replacement bushings are available in the "Help!" section of your local auto parts store. Look for the area with a variety of parts on red cards. The part number is 31018 and they come two to a pack. The pack also says "Ford/Mercury" on it, so if you can't find the "Help!" products, perhaps you can ask for a Ford/Mercury replacement. You will need two cards (or four bushings altogether). I paid $2.58 per card at Pep Boys. I would describe them as being about the size and shape of a medium sized mushroom cap; only, of course, with a hole through the center.

"Replacement is a breeze. I did both sides in a little over an hour. The biggest operations are jacking up the car, removing the tire, and removing the hinged side of the air filter on each side. Removing the old bushings and installing the new ones is a straightforward and simple procedure." Note: you can easily compress and release the shock while you're there, thereby checking that it's in good shape -- see above.

"The old bushings were the consistency of foam rubber after five years and about 25,000 miles. These were Jaguar replacements done after the car had traveled 32,000 miles over four years on the factory installed bushings.

"Bottom line: About $5.00 and an hour and a half of my time for a fix that should hopefully last a long, long time. This versus about $25 in parts and $75+ in labor to the dealer for a fix that would last, at most, about 30,000 miles."

Note that the XJ-S has steel washers that fit between the bushings and the chassis; purpose unknown, but it won't hurt to put them back in with the new bushings. Littlefield says, "The real purpose of the washers seems to be to let you know your bushings are bad by clanking around and driving you nuts until you replace them!"

Another common cause of clunks is loose diagonal supports across the top of the engine compartment. Make sure the bolts at both ends are tight.

Also check for a failed subframe mount. When the rubber within the mount is torn but still in place it would seem that it shouldn't make any sound, but it does. There are two doughnut-shaped mounts at the front, and two V-shaped mounts near the steering rack. If the rubber is torn or otherwise damaged, they should be replaced.

 

FRONT SUSPENSION CHECK: You may be confident that your front suspension is just fine, but this test is so quick and easy you might as well try it. Stand beside the car and grab the top of a front tire and shake it vigorously in and out. If everything is OK, the only thing you will feel is the flexing of the tires, and you will hear nothing.

If you feel any slop, or you hear a "clunk" back and forth, your front suspension is not up to snuff. You should check the following items, which are discussed in more detail below:

  1. Adjustment of the wheel bearings.
  2. Condition of the ball joints, upper and lower.
  3. Wear groove on bottom of front axle.
  4. Bushings at inner end of upper and lower swingarms.
  5. Front subframe mounts.

Perform this test and correct any problems noted before having your car aligned. The repair or replacement of ball joints, tie rod ends, swingarm bushings or subframe mounts normally requires realignment, and it's a shame to have to do it over.

It should also be noted that, contrary to common belief, a car will not periodically require realignment for no good reason. If a car was correctly aligned at one time and no longer is, it is because parts are either worn or damaged, and merely realigning without addressing those parts is unwise.

 

FRONT HUB REMOVAL: Michael Neal suggests the brake caliper not be removed when pulling the hub, to avoid fiddling with steering arm shims. Instead, unbolt the disk from the hub by inserting a socket through an opening in the dust shield. Then, remove the hub leaving the disk in place.

 

FRONT WHEEL BEARINGS: According to Chad Bolles, the XJ-S uses standard front wheel bearings, available in any auto parts store. The pre-1977 XJ-S outer is an A-2, the inner is an A-6. The 1977-up car uses A-13 for the inner, A-12 for the outer.

 

FRONT WHEEL BEARINGS/SEALS SERVICE INTERVAL -- ABS-EQUIPPED CARS: Bruce Segal reports from Canada: "Jaguar was recommending that the front wheel bearing seals be replaced every 15,000 mi (24,000k). At the same time the bearings should be looked at and replaced if there is any evidence of water ingress. I don't know if this applied anywhere besides Canada. We found that after going to this procedure front wheel bearing failures disappeared."

Stefan Schulz provides a possible explanation: "It could well be the likelihood of contaminant ingress that causes Jaguar to specify the change interval. The grease seal at the inside of the front hubs was changed with the advent of ABS. The pre-ABS grease seal looks like it will properly do the job, since it sits firm in the hub casing and its sealing lip rotates (and presumably experiences friction and wear) over the relatively smooth surface of the stub axle. The post-ABS grease seal works the other way round, it sits on the hub carrier and its lip touches the hub proper which rotates relative to it. The hub's inside surface in that area is nothing like as smooth as the sub axle's surface, so I'd expect that grease seal to fail much earlier."

"I have had my XJ-S for almost three years and 42,000 miles now. R&R'd stub axles and front wheel bearings when I bought it and bearings again about 10,000 miles ago. They needed it."

Segal again: "In my environment (winter, salt, water ) the new type seals do not provide a long term solution -- thus Jaguar Canada's very short replacement recommendation. We've found that quite often the bearings had started to rust front the salt water getting past the seal."

If you have an ABS-equipped car, perhaps while you have the hub off for an overhaul it'd be a good idea to polish up the contact surface on the inside of the hub to help seal life.

 

FRONT AXLE WEAR: The inner races of the inner front wheel bearings tend to turn on the axles. As a result, they eventually wear a groove in the axle, on the bottom where the load is. This allows the wheel to wobble even when the bearings are adjusted properly, and your Jag starts driving like a Pontiac.

To check for problems, remove the front hubs and check the stub axles for a wear groove. Run your fingernail along the bottom of the axle from the upright outward. If your fingernail catches at all, the axle should be replaced.

When assembling, ensure that the inner races will not turn by using Loctite 640 or some similar high-strength bearing retaining substance. Use it on the inner race of the outer bearing, too, since it has been known to have the same problem. Adjust the front wheel bearings as described below.

 

FRONT WHEEL BEARING ADJUSTMENT: Spin on the retaining nut until it seats, normally a very sudden change; continue to tighten while turning the hub until an increase in resistance in turning the hub is felt. This is usually about 1/10 of a turn after the adjustment nut starts to seat.

This may seem tight, and in fact may be tighter than the official Jaguar procedure (measuring end play) would result in. Any bearing expert will tell you that proper operation of a roller bearing requires some preload. It is better to be too tight than too loose. When tight, the weight of the car is distributed among the rollers. When loose, the slop allows the load to be taken by only one or two rollers at a time, and the unloaded rollers may slide rather than roll.

Note that having the bearings adjusted too loosely -- as well as having a grooved front axle, as described above -- would be detrimental to seal life. And the seals on the ABS-equipped cars may be marginal already, as mentioned above.

 

FRONT WHEEL BEARING CAPS: Apparently, some bearing caps are a total seal, while others have a small hole in the middle. It is suggested that if you have wheels that don't keep dirt out of this area, put a small piece of aluminum tape over the hole. Or, just pry it off and take it down to the local auto parts store and buy a generic replacement.

 

CHECKING OF BALL JOINTS AND TIE ROD ENDS: To test joints such as these, it is helpful to find a convenient way to "shake" them, or to move them in such a way that will cause them to slop one way and then the other. In the case of tie rod ends, this is easily done by moving the steering wheel back and forth just a little. With ball joints, if the front tire shaking described above caused a "clunk", that same motion will work for this test.

This test requires two people. Place a single finger on the joint in question in such a way that one side of the finger is against the hardware on one side of the joint, and the other side of the finger is against the other side. While holding this position (may be difficult, since the car should be sitting on its wheels) another person should provide the shaking motion. If the joint is OK, no motion can be felt between the two parts. If the joint is loose, a human finger will easily detect the slop. Typically, any slop at all is unacceptable, the joint should be replaced.

 

ANTI-SEIZE COMPOUND: See description earlier. This note is to point out that many suspension components involve tapered fits, such as the ball joints and the front axle in the upright. It is suggested that anti-seize compound be used on the tapers themselves as well as the threaded nuts. It does no harm, and can make the assembly much easier to get apart in the future. In tapered fit applications, care should be taken to ensure the entire fitting is thinly coated, since the anti-seize compound will not be spread during assembly as it is on threads.

 

FRONT SPRING COMPRESSION: If you're gonna fiddle with the lower ball joints, you need to be careful with that spring. Ideally, you should use a spring compressor that fits this assembly, but that may be difficult to find -- the front spring mounts on the XJ-S seem designed to confound most standard spring compressors. The official Jaguar tool is a threaded device that goes up the middle, so perhaps something can be rigged involving some threaded rod. Other suggestions include tying the suspension in the loaded position while it's sitting on it's wheels and then jacking it up -- please be very careful tying it, and make good and sure whatever you use is strong enough for the job. And keep your body parts outta the way anyway, just in case it breaks loose.

Another idea is to gradually unbolt the spring pan from the A-arm, replacing the bolts with progressively longer bolts until the spring pan is far enough below the A-arm that it is completely unloaded. Then the spring can be removed altogether. Works, but is very time-consuming and requires a lot of bolts of various lengths.

Others prefer to jack up the car under the lower A-arm itself, thereby keeping it loaded while you're working on the ball joint. Works, but be sure the spring plate can't slide off the jack while you're trying to get the ball joint to break loose. Dale Knaus says, "The way I change the ball joints is to start by blocking the opposite rear corner of the car at the jack point, and raising the wheel I am to work on by jacking under the spring pan on the lower A-frame. By blocking under the opposite rear, the jack will lift more of the car and compress the spring more."

 

LOWER BALL JOINTS: The original lower ball joint is a rebuildable assembly, with parts books listing the individual components. The lower ball joint from the XJ40 (the 1988-on boxy XJ6) is a one-piece throwaway item (part number CAC9937) that will replace the entire ball joint assembly on the XJ-S, and costs less than the individual parts of the original design. In fact, Jaguar no longer makes the original, rebuildable ball joint or parts to fit it; the authorized repair shops merely replace the joint with the XJ40 item.

An aftermarket parts company, Quinton Hazell, makes a rebuild kit for the original lower ball joint assembly. QH's prices for this kit are much more reasonable than the Jaguar parts prices ever were, and it is cheaper to use this kit to rebuild your ball joint than to install the new XJ40 unit.

The lower ball joint is assembled with shims to provide a properly snug fit between the ball and the socket. However, it should be noted that these shims are intended to provide a proper fit at assembly, not for removing the slop from a worn joint. If a joint develops slop, it should be rebuilt with new parts or replaced entirely, not merely readjusted.

When rebuilding the lower ball joint, don't lose the shims that come out. Although the QH kit includes shims, they are really intended to provide some adjustment capability from the original set; there may not be enough to provide all new shims.

When rebuilding the ball joint, thoroughly grease the ball and socket parts prior to final assembly. Although the joint has a zerk fitting, its use is no substitute for proper greasing at assembly.

The gaiter on the original Jaguar ball joint is a Rube Goldberg assembly in itself, and the parts are available separately. The gaiter itself is a clear flexible plastic item, with a steel ring molded into it to make the small opening fit snugly around the ball shaft. The gaiter fits into a plastic ring (C22970), and a rubber ring (looks like a skinny O-ring) fits into a groove on the gaiter to hold it snugly into this plastic ring. The plastic ring then snaps onto the ball joint. Be sure that the plastic ring is oriented properly; the little ridge on the inside must be on the edge toward the joint itself. It appears that the intention of all this complexity is to allow the gaiter to turn with respect to the ball joint as the steering is turned, rather than twisting the gaiter or allowing the small end to turn around the ball shaft; the plastic ring is expected to rotate in the groove on the ball joint.

The gaiter provided in the QH rebuild kit is different than the original. It is a more conventional solid black rubber item with no metal reinforcement. A metal clip is provided in the kit to be used in place of the rubber ring on the large opening. The kit does not include the plastic ring; if you boogered up the original getting it apart, it can be ordered separately. In a pinch, the gaiter seems to work just as well attached directly to the socket without the plastic ring.

If you are replacing just the gaiter itself and have neither the metal clip nor the rubber ring, you can simply tie it on with some wire. If using the QH gaiter, you can use nothing at all -- the black rubber gaiter fits quite snugly.

The original Jaguar gaiter has a life expectancy of less than five years. The clear plastic turns dark brown, then rots and falls out in crumbs. However, the gaiters in the QH kit are also British, so there's no telling if they are any better than the originals.

The ball shaft must be separated from the lower A-arm to replace the gaiter. Disconnect the upper ball joint to allow tilting the upright to get better access. Use of a fork-type ball joint separator on the lower joint will not only destroy the old gaiter, but the plastic ring and the upper ball seat as well. The fork type separator doesn't work very well here anyway; better to have the screw-type separator on hand. If the joint isn't jammed too severely, it is also possible to get the joint loose by disconnecting the tie rod and the brake line (helpful for getting the nut off anyway), jamming something between the inner edge of the hub carrier and the A-arm, and forcefully rocking the hub carrier outward.

 

UPPER BALL JOINT: The official repair manual calls for "Steering Joint Taper Separator JD.24", but we don't need no steenking separator! Put the car on jackstands and remove the wheel. Put a jack and block of wood under the lower ball joint and jack it enough that the rubber bumpers on the upper A-arm are not touching the subframe. Loosen the nut on the upper ball post several turns, but do not remove it. Lower the jack so that the rubber bumpers sit on the stops and the full spring force is applied to separating the joint. If you're lucky and the previous mechanic used anti-seize compound on the taper, you'll hear a pop as it comes loose. If more difficult, a little judicious tapping on the side of the upright may help.

Make sure to note where the shims are located between the arms and the ball joint. Even if you plan to have the car aligned, at least it will drive better on the way to the shop. The shims are supposed to lift right out, but they weren't made quite right. They tend to catch the bolt on the inner corner on the hook-shaped end. If this corner is filed slightly, reassembly will be easier.

The gaiter and associated parts on the upper ball joint are exactly the same parts as those on the lower joint -- see notes above.

 

FRONT SWINGARM BUSHINGS: The front swingarm bushings may be checked using similar methods as the ball joints, except that the bushings include some rubber so there will be some slight motion even in a perfectly good joint. Usually, the best indication that a swingarm bushing is bad is that some of the rubber is hanging out of it.

 

 

Steering

 

STEERING ARM SHIM: The steering arm bolts to the hub carrier with two bolts. At the rear (longer) bolt, there is a shim (it looks like a washer) that goes between the steering arm and the brake caliper. Don't lose it! Omitting this shim at reassembly screws up your alignment and distorts your suspension parts.

If you have lost the shim already, replacements are available in .004" and .010" thicknesses. To determine the thickness required, assemble the parts and tighten all bolts except the one the shim goes on. Measure the gap between the brake caliper and the steering arm with a feeler gauge. After assembly with the appropriate shims, be sure to have the car aligned.

 

ALIGNMENT: First off, note that while many cars are aligned only at the front, the XJ-S requires that all four wheels be aligned. Although there is really only one adjustment at the rear (camber), it is likely to take most of the mechanic's time if any adjustment is necessary; it requires that the driveshafts be unbolted from the differential unit and shims changed.

Randy Wilson sends a warning to be careful which alignment shop you choose to align a Jaguar: "The generic American tank has shims to align the front suspension camber and castor. These shims are placed at both the front and rear pivots of the upper control arm. By adding or subtracting shims equally at both ends, you change the camber. By adding or subtracting shims at one end only, you change the castor. Jaguars do not work this way, but look like they do to the uninitiated. The Jaguar has shims at the upper pivot just like the Chevy/Ford above, but they must be used as camber adjustment only with equal amounts of shim change at both front and rear pivots. The castor adjustment is done by a separate set of shims at the upper ball joint. If some hack jumps in there and adjusts camber and castor by staggering the pivot shims, you will end up with a car with a sort of correct alignment (dynamic castor gain will not be as Jag intended), but the car will just eat upper control arm bushings.

"The good news is that the XJ front subframe is one stout critter. Unless it has been seriously whacked, it is rare for camber or castor to need adjusting. Alignment is usually just a matter of setting the toe correctly after the latest steering rack change/rebuild."

There are reports that the spec books in the alignment shops consistently list the wrong alignment specs for Jaguars. Just to be sure, take your own repair manual with you, and if the numbers that you have disagree with those they have, insist they use yours. They shouldn't care, it's your car and your money.

There are some reports that the alignment of the XJ-S really needs to be done according to the procedures outlined in section 57.65.04 of the Repair Operation Manual -- namely, that the ride height must be restrained at a specified position for the alignment. The standard alignment shop shortcut of aligning the car at whatever ride height it sits at is not acceptable; both the front and the IRS geometries change with ride height, and many (most?) XJ-S's don't sit at the correct ride height by themselves. Failure to establish the correct ride height during alignment reportedly may result in a shaking in the front end at 50-60 mph -- a notorious problem in the H&E convertible, perhaps because the H&E convertible is also notorious for a low ride height.

If you're gonna pay your money for an alignment, you might as well insist it's done properly. Of course, it's not likely the alignment shop you choose will have the special tools used to establish the ride height on Jaguars -- unless you go to a dealer. So, if you're going someplace other than the dealer for the alignment, you'd be well advised to take the tools with you -- and the instructions from the repair manual showing how they're used.

The tools for setting the ride height of the front suspension are made from short lengths of tubing, and there's enough info to make them provided in section 57.65.04 of the Repair Operation Manual. The tools for setting the ride height of the rear suspension are a pair of metal hooks, and are described only as Jaguar tool no. JD.25. These would be even easier to make than the tubes, if only you knew what the key dimension was -- and just what is this book for, anyway? Figure 9 should provide the info needed about theJaguar Alignment Tool JD.25 

Note that although the official Jaguar tools are made from a single 9/32" steel rod suitably bent, there's no reason you shouldn't be able to screw together suitable tools from eye bolts, threaded hooks, threaded rod, and some coupling nuts -- all available at any hardware store for peanuts. Remember that you'll need to make two.

These tools might actually be a suitable thing for local Jaguar clubs to keep on hand for the benefit of their members. Apparently, these exact same tools have been used on all Jaguars that use the same IRS as the XJ-S -- which means all E-types, all XJ6/12 SI/II/III -- basically all Jaguars made for about four decades. In fact, the dimension shown in the drawing was provided by Michel Carpentier, who got it from a Mk10 service manual. At the time the Mk10 was made, the tool was called a J25; the tool names were changed to JD after Jaguar bought Daimler.

Note that when either end of a Jaguar is being aligned, the ride height setting tools should be in place on both ends.

In what must be considered a serious shortcoming, the Haynes manual does not discuss this ride height setting procedure at all, and lists an incorrect tool number (JD21 -- actually the number for a bushing tool of some sort) without going into any detail about using it. It suggests that alignment is not for the home mechanic, but provides a few generic guidelines for what is done -- just enough to get you in trouble. If you have only the Haynes manual, it is recommended that you obtain a copy of the alignment instructions from a Jaguar manual before having an alignment done by a non-Jaguar shop.

Finally, note that most of the above info probably applies only to the pre-1993 XJ-S with inboard rear brakes. From 1994 on, a completely different IRS was used with outboard brakes, and it presumably requires different alignment procedures.

If you'd like to try tackling the alignment job on your own, Tony Watts points out that there is a description of how to perform your own alignment with simple tools on the WWW at http://www.vtr.org/maintain/diy-alignment.html

 

STEERING COLUMN INSTALLATION: If you have lowered your steering column, Rob Reilly sends this tip for reinstallation: "When putting back the steering column use a little rubber cement to hold all the washers in place. Leave the bolts loose and pull the column back about 1/4" before you tighten them; if you don't, you will get binding in the lower column universal joint and bumpy steering."

 

STEERING RACK LUBRICATION: According to the John's Cars catalog, using the zerk fitting on the steering rack does more harm than good, and they remove them during their rebuilds. Others have reported no problems, but obviously one would be well advised not to get carried away with the grease gun. Stefan Schulz reports: "Perhaps even Jaguar realized that eventually, mine (CBC5708) doesn't have that fitting any more."

 

STEERING RACK LOWERING: The steering rack is mounted on slotted holes, so that either end can be repositioned up or down. The intent is to be able to position the rack properly with respect to the lower A-arm mounts, and there is a special Jaguar tool used to check for proper position when reinstalling. Presuming that you don't happen to have this tool laying around the house, it is suggested that you carefully mark the position of the mounting bolts within the slotted holes prior to lowering the rack. When reinstalling, simply put it back where it was.

Any time the steering rack is lowered for inspection or repair, it is wise to disconnect the bolts mounting the power steering cooler to the subframe. The pipes on this unit are very fragile, the hoses are short and often stiffened by age and heat, and a new cooler is of course more than $100. It can generally be repaired by any reputable radiator shop, however.

 

STEERING RACK MOUNT BUSHINGS: The mount bushings in the steering rack are parallel to the axis of the rack itself. Since the forces caused by steering are also parallel to the rack, the elastomer in the bushings is subjected to shear. This is a really lousy design; sound engineering practice is to avoid shear or tensile stresses in elastomers, and subject them to compressive loads only.

This book is organized such that this section covers maintenance only, modifications are later in the book. Many people probably feel that they do not wish to modify their car, and may not even read through that section. Please, please take the advice on replacing these rack mount bushings. Even if the stock bushings have not yet failed, even if the car is brand new, it is advised to replace them with alternative design bushings.

Contrary to the instructions in the manual, the steering rack can be lowered far enough to work on the mount bushings without disconnecting either the hydraulic lines, the tie rods or the steering column. The only difficult part is access to both ends of the three mounting bolts.

John's Cars offers a rental tool for removing the original bushings from the rack. It is extremely helpful, especially when working with the rack hanging under the car where a bench press won't help. Or, you can improvise such a tool using two 3/8" drive sockets (one with an OD a hair smaller than the bushing, one deep and large enough for the bushing to fit inside it), a long 5/16" bolt or piece of threaded rod with nuts and washers.

A method to avoid: Some people cut the rubber and center sleeve out, leaving only the outer sleeve, then insert a hacksaw and cut through the sleeve on one side; the sleeve can then be collapsed and removed easily. If done carefully enough, it appears to work fine, but a small nick on the aluminum boss on the rack can cause a stress crack later. Using a drill or other means to destroy the original bushing involves similar risks.

Another method to avoid: using a hammer. You're just asking for damage to that aluminum.

An obvious method to avoid: Heating the aluminum up to get the bushings loose. Unbelieveable as it may seem, some people are willing to try this. The facts that the housing is aluminum which conducts heat very well, the seals inside are rubber, and a rebuild costs as much as a three-day ocean cruise for two never occurs to them.

The stock assembly includes a sheet metal U-channel that fits around both bushing assemblies on the driver's side, holding the whole mess together as you offer it up to the car. When you lower the rack, this piece might stay up there; pull it out, it's helpful for installation. The aftermarket bushing set from John's Cars includes a new one of these pieces -- very nice, since the old one might be a little mangled.

Be sure that all rack mount parts fit snugly when assembled. Do not use the bolts to pull the frame in to meet the sides of the bushings. If necessary, buy some 5/16" fender washers and insert them alongside the mounts to make them fit properly.

 

STEERING RACK MOUNT BOLTS: If you happen to be working on the rack with either the engine or the front subframe out of the car, you may be able to put the bolts in any way you wish. But for the benefit of those who work on the car later, please install the upper mount bolt on the driver's side from the outside inward, and the lower bolts on both sides from the inside outward. This makes it much easier to install or remove the rack with the engine and front suspension in the way.

If you must replace the mounting bolts, be careful not to use bolts that are too long. When complete, be sure the upper bolt on the driver's side does not protrude too close to the engine block, since the engine moves on its mounts and will beat against the bolt. And the lower bolts should not protrude too closely to the lower A-arms, since they are likewise mounted on rubber and may move during operation.

 

STEERING RACK REMOVAL: If you have to totally remove the steering rack, one problem is how to remove the pinch bolt that connects the steering column swivel joint to the tower shaft. Remove the oil filter first, then turn the steering wheel until the pinch bolt is positioned where you can get at it.

Also note that the pinch bolt must be completely removed for the swivel joint to be disconnected from the tower shaft. The tower shaft has a recess the bolt fits through; merely loosening it will not permit removal.

You might find it helpful to carefully mark the relative position of these parts prior to disassembly.

 

STEERING RACK TUBE CHAFING: Stefan Schulz reports on chafing problems on his RHD car: "...above the rack on the left is where the pipes go to the power steering pump. On mine there is a designed-in problem where one of the pipes chafes against a bolt head. This cost me two replacement pipes before I figured out what was going on. No way to get around it with the Jaguar original parts.

"My steering rack is a CBC5708N, which is the UK (RHD) sports pack rack. The pipe is part of the high pressure hose assembly CAC3654 (same as the plain XJ-S). Calling it either hose or pipe is misleading because it consists of alternating sections of hose and pipe.

"One of the pipe sections either constantly chafes on or occasionally rubs against a bolt head near the upper left side of the rack, as seen from underneath the car facing forward. The severity of the chafe will depend to some extent on how much either end of the hose assembly is twisted against its fittings during installation. The design fault appears to lie in the fact that the offending section of pipe is dead straight (which is cheap) as opposed to having a slight bend to clear it (which costs at least an extra GBP0.02 to manufacture).

"Funnily enough, inspection of hoses and pipes for chafes is a part of the 7,500 miles maintenance schedule. No prizes for guessing why, in case any more such design gems lurk in the car.

"My workaround, which operates entirely satisfactorily, is to put a hose clip around the chafing area of the pipe, to check it every time I get under the car and to replace it when necessary. So far I only needed to do it once, after about two years of service. The pipe still is as new.

"A hydraulics shop could easily make up a properly formed section of pipe, probably at a fraction of the cost of a Jaguar original as well."

 

STEERING RACK TOWER SHAFT SEAL: This seal is prone to leakage. John's Cars offers an aftermarket seal that is supposedly better than the original. It better be, it's quite expensive.

Reportedly, one problem associated with this seal is incorrect installation by driving it too far into the housing. Be sure not to drive it any deeper than it needs to go.

 

STEERING RACK REBUILDING: There is a "seal kit" available for the steering rack. Note that reportedly the tower shaft seal is not included in this kit; check with your source and order the tower shaft seal separately if necessary.

A high percentage of people who have rebuilt their own steering racks have reported failure on the first try, and all for the same reason: when installing the rack bar through the seal on the driver's side end of the rack, the teeth on the rack bar ruined the seal. This typically results in ordering an entire new seal kit to obtain this one seal, and greater care the next try. The repair manual calls for wrapping the rack with tape prior to sliding the seal over it; apparently this is the minimal precaution, experience says to lube it up as well and exercise extreme caution during assembly. It has also been suggested that the seal and the part it mounts into be slid over the rack separately and then assembled, since installation in the housing makes the seal more difficult to work with.

 

STEERING WHEEL ALIGNMENT: If your steering wheel is cockeyed when driving in a straight line, your problem may be in the relationship between the steering wheel and the rack, or between the rack and the front wheels. Jaguar has provided a nifty method of determining which. If you remove the grease fitting from the steering rack, a dowel (or special Jaguar tool no. 12279) can be inserted to engage a notch in the rack. When the notch is lined up with the grease fitting hole, the rack is centered. The steering wheel can then be lined up properly. Once this is done, a misalignment when driving straight (be sure you're on a level road, and not in the right lane of a road that is crowned) calls for correction at the tie rods. If the correction is minor and you are confident that the alignment is otherwise OK, this can be done by carefully marking both tie rods and adjusting both of them the same amount.

 

TURNING RADIUS: Dan Jensen reports, "I recently replaced the power steering racks in my '83 XJ6 and '84 XJ-S with rebuilt units. After changeout, I noticed a significant, and undesirable, increase in the turning radius on the XJ6. This often made it difficult to make U-turns without backing up, and complicated parking. A check with my local Jag specialist revealed the source of the problem. Some point along the line, Jag added rack travel limiters as part of the inner ball joint lock tabs. These were apparently installed to preclude potential rubbing of the tires on front end components after Jaguar changed the recommended tire size from 205/70 to 215/70. I don't know if this applied to the XJ-S as well, which had 215/70s specified. By pulling back the inner ends of the rack boots, I could see the thicker locking tabs. I unscrewed the inner ball joints and replaced the wide tabs with the narrower tabs. This caused no noticeable change in toe-in since the thickness of the locking tab between the rack and ball joint is the same on both varieties of tabs. This was a 10 minute job and fully restored the tighter turning radius I was used to. I have not noticed any rubbing of tires on components with the 215/70's on the car. If others have what feels like a wide turning radius, you might want to examine one side of your rack to see what tabs are used. Apparently rack rebuilders are not always careful about the VIN number and rack changes, but I cannot see how the limiters served any real purpose and, in fact, created a bit of a hazard in my case when making U-turns."

 

POWER STEERING PUMP: According to XKs Unlimited, there have been three different power steering pumps used on the XJ-S. Prior to 1976, the part number was C28457, and the pulley was retained by a single nut in the center. From 1976-1980, part number C45540 was used, and the pulley was bolted to a hub on the shaft with three bolts. Also, the high pressure line connection is sealed with an olive, visible when the hose is removed. From 1980 on, part number EAC3167 was used and this pump looks just like its predecessor except that the high pressure line is sealed with an O-ring. This last pump is referred to as the "metric pump". The same three units were used on other Jaguars of similar years.

The XJ-S power steering pump is a standard GM Saginaw unit. However, it is uncertain whether the Jaguar system operates at the same pressure as a GM; so, if you replace the original unit, it is suggested that you remove the pressure control valve from the Jaguar unit and install it in the new one. The pressure control valve is easily removed by removing the outlet fitting and shaking the unit until it falls out.

 

POWER STEERING FLUID: You're supposed to put the same type fluid into the power steering unit that you put into the automatic transmission. This is interesting, since the early cars with the Borg-Warner automatics called for Type F fluid while the later cars with GM400 automatics call for Dexron II/III, and the power steering system didn't change. Apparently any ATF will do in the power steering system.

Apparently Type G fluid was called out in some owner's manuals for the power steering. "Type G is an obsolete designator for Dexron. It's so obsolete that nobody remembers what it was."

See the discussion on Dexron ATF's.

 

 

Rear Suspension

 

REAR END ALIGNMENT: There's no such thing as castor on non-steering wheels, and toe-in is not adjustable on the rear of the XJ-S; if it's off, something is bent. The only alignment adjustment available at the rear is the camber, adjusted by replacing shims between the inner end of the axle and the brake disk. The more shims put in, the more the top of the rear wheel tilts outward.

Note that there are usually some shims between the brake disk and the differential unit. These are to locate the disk properly between the calipers, but also affect the camber as well. If working in this area, always make sure all shims are reinstalled properly.

Randy Wilson offers this advice: "Camber is not a constant. The camber control is taken on two pivoted arms (of unequal length) so that the camber can change on a predetermined curve based on suspension position.

"It is very unlikely for the camber to change from factory specs unless one of three things happens: either something is bent, someone left some shims out during a differential or brake service, or the ride height is wrong. The #1 cause is the last, sagged rear springs. So, when you are told that the rear camber is off, investigate the static ride height before investing a lot of time/money in shim swapping."

 

CLUNK -- REAR: See the section on the Drivetrain.

 

REAR SUSPENSION SUBFRAME/DIFFERENTIAL REMOVAL: To work on the differential, as well as many major tasks relating to the rear brakes, it is necessary to lower the entire rear suspension assembly out the bottom of the car. Fortunately, this is nowhere near as difficult as it appears. Jan Wikström says "You need two good stands and a small garage jack, as well as a friend to stabilise the subframe as you move it down and up (and help you lift it to the workbench; that sucker is heavy). To make the job a lot easier, take the spring/shock units out first and refit them last. You'll need to shift the subframe in two lifts, as the stroke of the jack won't be long enough. I use a 5" thick wooden block on the jack and rest the unit on two cement blocks halfway up."

Some others have reported good results with putting the wheels back on during removal; that way, the assembly can be rolled out from under the car. It will require positioning the car on even taller stands, though.

 

REAR SPRING/DAMPER DISASSEMBLY: The obvious way to disassemble the springs from the dampers on the rear end is to remove the damper with the spring installed, then use a spring compressor on the bench to separate them. However, Ian Macfarlane provides an alternative procedure: "To change the rear shock absorbers without using a spring compressor, the springs can be held in the compressed state by fitting four elongated "C" shaped brackets (two per spring) over the centre 80% of the spring with the car jacked up under the suspension (preferably with a load in the rear of the car to maximize spring compression). Then, when the car is jacked up under the body, the springs will remain partly compressed and the shock absorbers can be replaced relatively easily."

 

REAR WHEEL BEARINGS: According to Chad Bolles, the bearings in the rear wheel carriers are a Bower/BCA part number 18590-18520 for the inner, and 18690-18620 for the outer; available in any auto parts store.

 

REAR AXLE FAILURE: Jan Wikström reports on his problem and solution: "The stub axle in the hub carrier (the bit that turns in the rear wheel bearings) is splined for the hub and has a large thread and castellated nut on its outer end. This thread comes right down to the splined part with no fillet whatever and creates a horrendous stress concentration at the end of the thread. Mine suffered a fatigue fracture in consequence; my local parts pusher tells me this is not uncommon, as one would expect from such an elementary error, especially if the nut is overtightened. Accordingly, I ground and polished a shallow rounded groove at the base of the thread of the new part... (see Figure 10 and Figure 11, illustrations graciously provided by Wikström).

"The next time you do the rear wheel bearings or U-joints, I strongly recommend having the stub axles checked and modified; any competent engineering shop will know about stress relief. Modifying parts of the Jaguar may be sacrilege to some of us, but fine as the design is, it isn't perfect..."

If the stub axle has already broken, it is possible to fix it by drilling and tapping a hole in the end and using a bolt and washer instead of the nut. GT Jaguar offers a grade 8 bolt and a specially designed washer for this purpose, although you could conceivably come up with suitable parts from local sources. This fix may also be used as a preventative measure, since cutting off the stub and drilling for the bolt eliminates the stress concentration in the original part as well as the shallow groove does.

Perhaps one thing to note is that GTJ offers these parts at all; that would seem a serious indicator of just how common this problem is, and how important it is to address it.

 

REAR HUB CARRIER CRACKING: Joe Bunik reports that the cast aluminum hub carriers on his car cracked in the area just above and outward of the fulcrum shaft. The crack was parallel to the fulcrum shaft, but just far enough above it to be in the structural portion between the fulcrum shaft bearings and the wheel bearings. According to his mechanic, this is not an unusual problem.

Folks, if this part breaks at speed, you will be taking the Lord's name in vain! These parts are expensive, but if a crack is found it would be foolish indeed not to address it.

What with the rough surface on the cast aluminum combined with the dirt and grime normally covering it, it is entirely too easy not to notice a crack like this. Whenever a rear wheel is removed, it is recommended that the hub carrier be cleaned up a little and inspected for cracks, especially in the area just above the fulcrum shaft.

 

 

Wheels and Tires

 

SPOKE WHEELS: Yes, a Jaguar with real spoke wheels really looks good. Unfortunately, it generally doesn't drive worth a hoot. The spoke wheels available have a reputation for trouble. Spoke wheels were a good idea in the ë50s when Jaguars needed to maximize air flow to cool their brakes. Since that time, two changes have conspired against spoke wheels:

1. The advent of tubeless tires. Many spoke wheels won't work with tubeless tires, so you must install a tube. A tube installed in a speed-rated tire (the XJ-S should be fitted with V-rated tires) completely negates the rating, and renders the tire unsafe at speed. Don't drive fast with inner tubes in your tires!

2. The advent of low, wide tires. A spoke wheel is a reasonable structure when it's tall and skinny, like a bicycle wheel or the automobile wheels of the ë50s. But it is a structurally poor design for modern low, wide wheels.

Furthermore, modern Jaguar wheels need an offset (distance from mounting surface to centerline of wheel) of around 1º", which is not conducive to spoke wheel strength.

Spoke wheels tend to need truing on a regular basis. This is not a job for the home mechanic, and finding someone who can do it is a challenge. Often the wheels must be returned to the manufacturer for truing. Obviously, whoever does it, this process will also require rebalancing because the wheel is not the same shape as it was.

Spoke wheels generally have chrome-plated steel rims, leading to rust problems, flaking chrome, and associated leakage at the tire/rim seal.

By the way, if it's a weight reduction you expect, forget it. There is nothing lightweight about spoke wheels.

It should also be noted that since the spoke wheels are more flexible than alloy, the handling will suffer somewhat. With a car this heavy, the difference in the way the car corners is noticeable. You may even get sounds, as the spokes strain and creak with the load.

 

ALLOY WHEELS: The specified torque on lug nuts on earlier Jaguar alloy wheels is 45-50 ft-lb., and 75 ft-lb. on later ones. This impresses some people as not being very tight. However, higher torque is unnecessary and causes damage to the aluminum wheels; this is true of all alloy wheels, and in this day and age your tire store should know better. If the shop installs your wheels with an air wrench, tell them where to get off and take your business elsewhere.

There are now machines in better tire stores that mount tires on wheels by gripping the wheel from the inside with soft grippers and never touching the wheel's pretty outside surface. Check out the price lists for new Jaguar alloy wheels and decide for yourself if it's worth finding a store with this equipment.

You might also want to watch how the wheels are mounted on the balance machine.

 

ALLOY WHEEL SEIZING: Believe it or not, one of the places where Jaguars are known to have seizing problems is between the alloy wheel and the hub. Robert Woodling suggests use of anti-seize compound on the mating surfaces, especially at the hole in the center of the wheel. It can be disconcerting to have a flat tire and be unable to get the wheel off.

 

WHEEL BALANCING: Incompetence is rampant in the retail tire industry -- at least in Florida. Left to their own devices, most of the meatheads in a tire store will happily static balance your Jaguar alloy wheels, then beat the weights onto the rim with a hammer.

There are two basic types of imbalance. The old-fashioned bubble balancing, which engineers refer to as static balancing, only corrects one type of imbalance -- the type that causes the wheels to hop. This is generally adequate only for wheels that are very narrow, and should be considered unsatisfactory for any modern automobile.

The other type of imbalance, dynamic imbalance, is the type that causes wobble. A wheel that is statically balanced may still be dynamically imbalanced by having a heavy area on the outside edge of the wheel and an equivalent heavy area 180 degrees away on the inside edge. Although the wheel would appear balanced on a bubble machine, when spinning the two diagonally opposite heavy areas cause the wheel to wobble. It's usually not too noticeable on the rear wheels, but on the front wheels it can cause steering wheel shudder. And you may eventually wanna rotate the rear wheels to the front, so it's kinda nice to have them all correct.

To correct a dynamic imbalance requires that weights be placed in two separate planes -- usually (but not necessarily) the inside and outside edges of a wheel. It requires more lead than static balancing. It also requires a machine that actually spins the wheel; the bubble balancer is out. Use of these machines has come to be called "computer balancing". However, note that a switch on the machine allows the operator to specify a static balance only, so asking for "computer balancing" does not guarantee a proper dynamic balance.

The meatheads generally understand that the owner of alloy wheels is not thrilled about balance weights on the visible outside surface of the wheel. The standard response is simple: he sets the balance machine on "static" and applies all the balance weights to the inside rim of the wheel. This actually makes the dynamic imbalance worse, since even in the days of the bubble balancer the operator knew to put half the weight on the inside edge and half on the outside.

Insist on watching what is going on. There is a button marked "static" usually at the top left on the machine, with a red indicator light. When on, the machine will read imbalance values on the left indicator and a blank display on the right indicator. If you see this happening, I highly recommend you have your wheels put back on your car and take your business elsewhere.

The balance weights needed are part of the problem. Steel wheels commonly use "clip-on" weights that are hammered onto the rim. Some alloy wheels are designed with a rim that can accommodate clip-on weights, but they may not attach as well to the thicker aluminum. And use of a hammer to install is not good for aluminum, especially if the meathead responds to difficulty with a bigger swing.

When the steering on an XJ-S is turned full lock, the clearance between the inside edge of the wheel rim and the front anti-roll bar is very small. If wider-than-original wheels are used, clip-on balance weights may actually hit the bar, resulting in a blip-blip-blip as you roll around a tight turn.

The proper balance weights to use on alloy wheels are called "stick-on", and are attached to the inner surface of the wheel with a layer of foam tape attached to the back side of the lead weight. One problem is that they are not reusable; once peeled off, the tape is not reusable, and the shops customarily throw them away. I guess using generic foam tape has not occurred to them, or just isn't worth it, even though they often complain loudly that these weights are expensive and charge the customer accordingly.

The problem is exacerbated by the meathead not knowing how to use the machine properly and having to do a by-guess-or-by-gosh balance job. With the clip-on weights, he can just keep prying them off and reinstalling them until he gets it right, but he can waste a lot of stick-on weights. An intelligent operator, of course, will be able to set the machine up properly and get the correct weight applied the first try.

The older computer balance machines were really designed for steel wheels. They have a setting for the width of the wheel and assume you will be putting clip-on weights on the edge. While the machines have a setting labeled "Mag", it is unlikely the operator will know how to use it. If you are using stick-on weights (which are located radially inward and on different planes than clip-on), the machine must be set up properly in order to read the correct amount of weight required. Simply setting the same width, offset and diameter info as used on the steel wheels will indicate if the wheel is imbalanced but will give incorrect data on the size balance weights needed, so the operator will be making several attempts.

There are newer balance machines that better accommodate alloy wheels. They can properly balance the tires by applying weights in any two planes, not necessarily the outer edges; the desired location for the weights is a separate setting in the balance procedure. They also can "split" a large balance weight requirement into two smaller weights, telling the operator where to put them both. This is helpful for two reasons: first, a large stick-on weight means a long stick-on weight, and as it curls around the rim its effective radius reduces somewhat, and the balance becomes inaccurate. Second, using two smaller weights may allow the operator to hide them behind spokes on some wheels.

Owners of alloy wheels should always insist on dynamic balancing using stick-on weights in two planes within the wheel -- one near the inner edge, and one just inside of the outer face of the wheel. Since these planes are closer together than the edges of the wheel, even more lead will be required to correct imbalances. But the weights won't show, and nobody will need to use a hammer to install them. Always insist that the balance machine shows 0.00 on both indicators before the balance is acceptable.

The only real problem with stick-on weights is a reputation for getting lost. Since clumps of mud and other debris sometimes gets dragged around the inside of the wheel, the foam tape can be ripped away. Two suggestions are in order, and neither is likely to be done by the tire shop, so the owner should bring the materials necessary and do them himself while the wheels are off: First, mark the locations of the stick-on weights with a permanent marker. Then, secure them with a piece of aluminum tape (available at air conditioning shops). Duct tape is not good; it quickly dries up and falls off, often taking the balance weight with it. The aluminum tape appears to be light enough to not affect the balance when added; or, to be safe, you could simply add a dummy piece of tape on the opposite side of the wheel.

 

WHEEL INTERCHANGABILITY: A few years back when Jaguar introduced the Anti-lock Braking System (ABS), they also introduced the new faux spoke pattern alloy wheels. Some reports at the time suggest these changes were related; apparently, the older wheels (a domed 5-spoke alloy design) interfered with the ABS hardware. The bolt pattern, offset, width, and other dimensions remained unchanged, so the later wheels can be used on earlier cars. But if the reports are true, the earlier wheels cannot be used on later cars.

 

XJR-S: John Goodman reports that the XJR-S uses "8" wide special alloys (the front and back wheels are not interchangeable because of different offsets)."

 

TICK, TICK, TICK: William C.W. Lamb had an irritating tick from one of his wheels. He was all set to tear into bearings when Roger Homer pointed out that it may just be the Jaguar logo in the center of a wheel cover coming loose. "Pulled both hubcaps - it was the kitty on the right rear. Quick fix with duct tape and some black RTV!"

 

TIRES: The early US-spec XJ-S was fitted with 215/70VR-15, and the later models with 235/60VR-15 tires. The wider tires are slightly smaller in diameter than the earlier, but there is no indication that Jaguar altered the speedometer or suspension. Both sizes are very suitable for the car, and there is normally no reason to select tires beyond these sizes. 16" wheels were also fitted to some later cars.

When replacing tires as a set, you don't have to stick with the brand of tire that came on the car. In fact, it may be better to change brands according to Michael Neal, who works on Jaguars for a living: "I've seen hundreds of the 215/70 Pirelli P5s rip out at the sidewall near the bead. These are the original equipment tires on the US-spec XJ6 Series 3s and early XJ-S's. Sorry, but I would not even consider buying a set of these. The 235/60 P600s had the same problem."

You should insist on at least a V-rating (a speed rating of 220 Km/h, or 137 mph) unless you always obey the US speed limits. In some countries, you are required by law to use V-rated tires on these cars. The rating is either indicated within the tire size, as in 215/70VR-15, or elsewhere on the sidewall, as in a 98V adjacent to the tire size. Other ratings include S (180 Km/h or 112 mph), T (190 Km/h or 118 mph), H (200 Km/h or 124 mph), and Z (250 Km/h, or 155 mph), and new speed ratings higher than Z seem to be introduced on a regular basis. In the US, if there is no indication of speed rating, the tire is S-rated.

These ratings are intended to indicate suitability for Autobahn-style driving -- continuous high speed. Generally, the limiting factor is heat buildup in the tire. High-speed-rated tires either run cooler or are made of higher-temperature material, or both. Much of the heat generated is dissipated to the air inside the tire and away through the rim, so inner tubes invalidate the ratings (the flexing of the inner tubes themselves adds to the heat buildup). There are also concerns about how patching holes affects speed ratings; it is recommended that the owner check the literature that comes with the tires before opting for a low-cost "plug" repair to his tires.

Since the flexing of the tire is what generates the heat, tire manufacturers usually achieve a high speed rating by making the sidewalls stiff. Therefore, the high-speed-rated tires drive differently than normal tires, even at low speed. For this reason, many recommend the V-rated tires even to those who don't drive fast. This is especially true for the XJ6 and XJ-S, because the soft suspensions get downright mushy with the softer, lower rated tires. There are reports that S-rated tires used on these heavy cars will flex so much that they will wear out quickly.

The heat buildup due to tire flexing is also the reason you must have fully inflated tires when driving fast, as indicated in the XJ-S glovebox.

As the tread wears, the speed rating of the tire will actually improve. A thinner carcass generates less heat when flexing, and dissipates heat better. There have been promotions claiming street tires were successfully used for racing; in these cases, typically the outer half of the tread was shaved off before the tire was even put on the car.

One other thing to consider when replacing tires is the intentions of the tire design. The original Pirelli P5's were designed for a soft ride, and the Z-rated 235/60 Goodyear Eagle NCT's fitted to the later XJ-S reportedly also provide an excellent ride -- actually an impressive achievement when maintaining a V or Z rating. Most V-rated tires are designed more for performance than ride, and replacement with such tires is likely to result in vastly better performance and road feel but a less luxurious ride. A set of Dunlop SP Sport D40 M2 235/60-15's (unidirectional tread, max pressure 44 psi) convert the XJ-S from a luxury coupe into a GT. Similar results have been reported with Yokohama performance tires.

Note that the Pirelli P5's are not available any more, and reportedly the Goodyear Eagle NCT's have stopped production as well. In fact, Bill Weismann reports that Goodyear makes nothing V-rated or better in 215/70R-15 or 235/60R-15, and their dealers will often try to sell you a lower-rated tire.

For those who'd like to know, the rest of the tire size code works like this: The first three digits, such as 215, is the width (mm) of the tire at the widest point -- the middle of the sidewall. It is always rounded to a number ending in 5. The two digits after the slash, along with an implied decimal point, gives the aspect ratio: the height of the tire above the rim divided by the width described above. For the 215/70VR-15, this is .70, and the height of the tread above the rim is 215 x .70 = 150mm. If there is no aspect ratio indicated within the tire size, the aspect ratio is .80. The R in the tire size merely indicates it is a radial tire; it is sometimes omitted. The -15 indicates it fits a 15" wheel.

The one thing you normally don't want to change is the overall diameter of the tire, since this would affect your speedometer and odometer readings as well as your ride height. Changing the ride height can have adverse effects on the suspension geometry, even if you don't mind the altered ground clearance. To maintain overall diameter when you go to a wider tire, you also have to change the aspect ratio to a lower value. Tire manufacturers also usually list a "loaded radius", the distance from the ground to the center of the wheel with weight on it. This measurement is meant to include the deformation of the tire under load so the consumer can determine the actual ride height.

FYI, Peter Cohen checked The Tire Rack (January 1998): "Here is what www.tirerack.com lists for 235/60X15:

Make and Model

Price

Speed Rating

Tire Type

Dunlop SP Sport D40 M2

$83

V

Ultra High Perf.

Yokohama AVS Intermediate

$119

V

Ultra High Perf.

B.F.Goodrich Comp T/A VR4

$89

V

Ultra High Perf. All-Season

Goodyear Eagle NCT

$158

Z

High Performance

Pirelli P600

$162

V

High Performance

B.F.Goodrich Radial T/A Raised White Letter

$68

S

Perf. All-Season

Dunlop GT Qualifier Raised White Letter

$57

S

Perf. All-Season

Firestone Firehawk SS10 Raised White Letter

$58

S

Perf. All-Season

General XP2000 II Raised White Letter

$58

T

Perf. All-Season

Goodyear Eagle GT II Raised White Letter

$71

S

Perf. All-Season

Goodyear Eagle #1

$75

S

Perf. All-Season

Firestone Firehawk FTX

$71

T

Standard Touring

B.F.Goodrich Comp T/A R1

$130

Z

Competition

B.F.Goodrich Comp T/A Drag Radial

$135

R

Competition

David Littlefield suggests you also check http://www.tires.com "This is the website for Discount Tires Direct, an online version of Discount Tires stores. The Discount Tire site will allow you to look up the right size tire for your vehicle. It gives prices for most tires, although for some reason not for Michelins. You have to call their 800 numbers for those."

Do not mix tire types, sizes or makes on a Jaguar. The XJ-S and the XJ6 have a suspension design in which the entire suspension assemblies are attached to the car with flexible mounts, and the relative stiffness of the mounts is premised on all the tires being the same. Mixing tire types, even outwardly similar ones, can result in dangerous instabilities in this suspension system. This is no joke; having one type of perfectly good tire on one end and another type of perfectly good tire on the other can result in you being rudely introduced to a tree when you aren't even traveling that fast.

 

TIRE PRESSURES: John Goodman says, "Most of us here (UK) have long junked our 15" wheels and run 16" or 17" rims, but the less competitive drivers, or those who do a lot of city streets always keep the tyre pressures down quite a bit. We run them up to 8psi lower than the handbook stated figures. My handbook says 35psi front and 32psi rear, so I run at 30 front and 27 rear. On 245/50 or 225/55 x 16" this gives only very slight loss of handling at extremes of cornering, but a very noticeable improvement in ride comfort. Has no effect on tyre wear either. This was a local Jaguar dealer recommendation!!!" Note: perhaps a workable plan for those who value ride quality, but high continuous speeds should be avoided without full pressure. Also note that lower pressure will provide less protection for your rims, so don't drive over curbs at speed.

Interestingly, the earlier XJ-S's took the opposite tact, and recommended rather low tire pressures (on narrower tires to boot!) and then recommended you go to higher pressures if driving fast. Perhaps the recommended pressures on Goodman's car are due to it being an XJR-S, and a sportier ride and high speeds are assumed.

Regardless of the peculiarities of one XJ-S vs. another, one thing must be pointed out: the nearly religious devotion many automobile owners pay to the "recommended tire pressures" is completely uncalled for. As long as you don't exceed the pressure limit written on the side of the tire itself, tire pressures can be varied considerably to provide the owner with the desired performance and ride. If the balance doesn't seem right to you, you can also vary the front/rear pressure distribution to alter it.

For optimum tire wear, an excellent plan is to keep an eye on the wear at the edges of the tires vs. the center. If they're wearing faster in the center, lower the pressure; if they're wearing faster at the edges, raise the pressure. This helps configure the car for the owner's driving style, since a driver that corners hard will scrub the corners of the tire more and should be using higher pressure. It even helps compensate for drivers that dive into turns as opposed to drivers that accelerate through turns, since the different styles will cause different tire wear patterns and correspondingly altered pressures. Of course, bad alignment or other complicating factors can easily screw up the data.

If you can't tell, the XJ-S is nose heavy, and one would expect that the front tires will always need more pressure than the rears -- unless you're carrying sandbags around in the trunk.

 

WINTER TIRES: In some states, you are required by law to have either snow tires or "all season" tires on your car during the winter months. According to Bill Weismann, "For a tire to be labeled "All-Season" it must be labeled (By federal law...) "M+S" on the sidewall. The only tire that properly fits the XJ-S in this size (Radial T/As, for example, are all-season, but are of a grossly lower speed rating) that is an all season is the Comp T/A VR4. Believe me, these things are terrible in the snow; OTOH, P600s are actually decent in the snow for a summer-compounded tire.

"It's a lot more than tread design that qualifies a tire as an all-season; the main problem with High Performance tires is that they have to be at somewhat high temperatures in order for them to "stick". An all-season tire usually offers two features for it to work in the snow.

1) A tread compound that will remain pliable in the cold (below 40 F or so..)

2) A tread design that will work in snow. Look at, say, a Comp VR4 vs a D40M2, you'll see that the D40's tread design consists of mostly large blocks, while the Comp's tread design is broken up a lot more. I have owned both and can assure you that the D40M2 (For reasons other than this btw..) will easily outhandle the Comp VR4. I also know from personal experience that the D40M2 is like a racing slick in the snow."

If you choose to purchase a separate set of snow tires for the winter, you should also note that, in snow, the narrower the tire, the better. For the XJ-S, you'd want to go back to the 215/70R-15's, and possibly even to a 195R-15. You also, of course, will want to find some really junk wheels, since snow, sand, and salt make alloys look really crummy very quickly.

You might also wish to carefully consider your options. Winter driving often involves snow, ice, and mud -- as well as a far portion of nice, clean pavement, since many road departments are really good at keeping roads clear.

One highly-rated type of snow tire is called a Blizzak which has a porous compound that grabs snow and holds on until it looks like your tires are made of snow; they work really well on dry snow, but are reportedly not much good in mud, wet snow, ice, or dry pavement, and they wear quite rapidly on dry pavement.

Studs are another option that the owner might regret. Great on ice, but not particularly beneficial anywhere else. Also, they will damage pavement, so they are frowned upon or downright banned in some areas. They also seem to have a detrimental effect on the rolling resistance of the car, so your fuel economy gets much worse and the car feels like the brakes are dragging or something.

 

 

On to Body Maintenance

 

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