11.4 - Castor and Camber Settings Explained! ( Scott/Saltwick/Westneat/Grant,  December 8, 2005 )

Castor & Camber explained

Lee Scott asked on 12/07/2005:

I got the front end aligned on the 420, which took care of my tire
squeal issue.

The report I got from the tire shop after it was done says :
camber: 1.1 degrees on the left, .5 degrees on the right
caster: -.8 degrees on the left, -1.6 degrees on the right
toe: .05'' on both.

Then there's this:
cross camber: .6 degrees
cross caster: .9 degrees
set back: .27 degrees.

What is cross camber and cross caster and set back?? Never heard
of these terms. What should the ideal settings be for all these
measurements? The tire shop didn't have the specs for the 420, so
he was using settings for a 69-70 E-type for reference.

Do I need to add/remove shims to adjust my castor and camber?


Clark Westneat responded on 12/07/2005 with:

Lee,
After the re-build on the 420, I mounted the front suspension back onto
the car -- did an eyeball alignment and took it down to my local guys. They
used the AllData specs for the 1969 XJ6 Series 1. We ended up having to
remove and replace shims on the "cage" for the suspension as well as the
wheel alignment. They used a laser alignment tool to make sure it all
aligned properly. It has been about 35,000 miles now and I still have
straight wear on the tires and no mis-alignment

I believe the cross camber and set-back is the relationship to the rear
alignment -- but I could be wrong.

Paul Saltwick responds on 12/08/2005 with:

Hello Lee,

The specs for your car are:

Camber: 1/2 degree +/- 1/2 positive
Castor: 0 +/- 1/2 degree
Toe-in: 0-1/8''

Your camber is (almost) within spec, but far from ideal if you are
running radial tires. It is normal to run more positive camber on
the left, around 1/4 degree, to compensate for the crown in the
road. 1/2 degree negative camber will give your car more grip and
better turn in with radials, at the expense of more inner tire
wear. You add shims to the top wishbone to get more negative
camber.

Your castor is out of spec. You never want negative castor. If
you run +2 degrees, the steering will feel better and self center.
There should be 8 shims and a packing piece with the upper ball
joint assembly. You adjust the caster by swapping them from side
to side.

Toe is OK.

Lee Scott responds back on 12/08/2005 with the following:

Paul,

Thanks for the info. If I understand you correctly, what I need to
do is move one or more of the shims from the back side of the upper
ball joint to the front side to adjust the caster in the direction
it needs to go? Any rough estimate on how many degrees each shim
swap will change the caster measurement?

Paul Saltwick responds on 12/08/2005 with:

Lee,

1/4 degree for each 1/16'' shim. Measure the shims with a caliper,
there are several different sizes for the camber adjustment and
they often get mixed up. Moving shims from the rear to the front
increases positive castor. The shims are slotted and you should be
able to lift up one side, after you jack up the lower ball joint
and loosen the upper ball joint bolts. If you have never shifted
the camber bolts, they often become frozen and heat, penetrating
oil and patience are needed. I recommend replacing them and using
anti seize if/when the subframe is out of the car.

Gary Grant adds in on 12/08/2005 with:

Cross caster is merely a measure of the difference between the
caster value on the right wheel, and the caster value on the left
wheel.

Cross camber is just a measure of the difference between the camber
value on the left wheel, and the camber value on the right wheel.

Set back is any front to rear difference in the positions of the 2
tire-to-ground contact patches. For example, if the RF wheel
contact patch happens to be 1/4'' more to the rear than the contact
patch of the LF wheel, there is 1/4'' set back on the RF wheel. In
other words the wheelbase on the right side of the car is 1/4''
shorter than the left side wheelbase.

And finally Lee Scott responds on 12/08/2005 with:

Thanks to all! Now I think I know what I need to know. What a great
source of info this forum is!