I'm knee deep in front-end alignment now and have come up with something that doesn't square with other info I've come across. I understand that caster for my year should be 3 1/2* +- 1/4*. My initial test on right side was 2.1*P so I took the wheel off and saw two shims on each side of the ball joint. I moved the rear shims to the front and now I have 2.7*P, but that is the limit of adjustment. Has anyone out there gotten more positive camber than that and if so, how? The initial test on the left side may be even worse, 1.9*P with two shims on each side of ball joint.

I won't get a chance to give it a road test this year, but I would like to get the settings to spec.

Thanks

Dave

 

Dave,
You mention 2 different specifications here. By your shim work you're working on Caster but you mention Camber too. I assume the Camber mention was a result of Caffeine Deprivation and you're doing battle with Caster.

I understand how you want it to be *Right* and nothing short of *Perfect* will do.
But.
You have changed SO many things during your rebuild (as we all do) that are all connected and all influence each other, that you may have created a whole new "right," if you understand what I mean.

Caster has a limit of adjustment as you discover, but is also influenced by Lower Wishbone bushings placement on the fulcrum shaft according to the ROM. It may also be influenced by Poly vs Rubber bushings and how different materials react (or don't) to installation of other components.

I set Nix's Caster to maximum as I like quite a lot of caster, but it only tested at L=3.1 degrees, R=2.5 degrees. These values seem to be just fine on the road.
(';')

 

I did alignments on Fords and Chevys in the late 70s, early 80s and the way we set BOTH castor and camber on many cars was the shims for the upper control arm.

You can set castor by moving a shim behind the upper arm mount from front-to-back or back-to-front and it will not change camber.
You can remove or add an equal number of shims front and back and it will change the CAMBER and not the castor.

Jaguars are not supposed to be set that way but it can be done that way.

 

Yes exactly!
In fact, when Nix came to us this is how some tech in the past had adjusted the caster, by using shims on only the front upper fulcrum shaft.


The ROM specifically advises against this as the shaft is designed to be parallel to the frame and shims placed in this location are said to accelerate wear on the upper bushings.

(';')

 

"The ROM specifically advises against this as the shaft is designed to be parallel to the frame and shims placed in this location are said to accelerate wear on the upper bushings."

I might be missing something, but I don't understand why. If the axis of rotation of the upper wishbone is slightly different from the lower, what dramatic effect does it have? After all neither of them are parallel to the centre-line of the car.

 

I believe that if the two fulcrums are not parallel in the same plane, as the suspension moves there will be unwanted, and undesigned-in, twisting effects on the upright, which will mean unwanted caster, toe, and camber changes as the suspension moves up and down.
The handling and driving feel of the Jaguar front suspension on this era of car is very sensitive to the alignment being dead-on, and the car will not feel, turn-in, corner, or drive as it should if it is not. Certainly my car is night and day different if it goes out of alignment. I am 100% certain that Jaguar did not specify the correct method of adjustment just to annoy people 60 years later. There is nothing to be gained and lots to lose by short-cutting the adjustment system, so why do it ?
As for being parallel to the centre line of the car, almost all suspensions incorporate anti squat (on acceleration) and anti-dive (on braking) geometry, and I understand that the "set" of the suspension fulcrums is the main way this is achieved.

 

Elinor,
I guess at midnight my proof reading needs to be proof read. Yes, caster was my intended topic. As you say, everything that moves in the suspension has been replaced and there was no evidence of anything out of sorts. The 4 caster shims allow about 1* total change, I would think the designers of the car would have built in more adjustment range if 3 1/2* was their target setting.

I'm with you that what I have is the "new right" for my current suspension. Your opinion is well received, thanks.

Dave

 

Thanks for the reply Peter, but I have to disagree with the practice of shimming only one side of the upper/inner control arm to adjust caster. From a mechanical view point, doing so puts every attachment spot out of square with the mating part. This diminishes the strength and holding ability of the bolt.

In real life, a one-sided adjustment, like Elinor's picture, would probably hold OK, but why do it wrong when you know how to do it right? I think Greg covers the geometry side of the issue pretty well.

Dave

 

I agree. It's ugly attaching things at an angle that were made to fit flat. If there were tapered shims, it might be acceptable. As for changes in caster, camber and toe-in, yes it will have a small effect, but they are changing anyway by significant amaounts with suspension movement and steering. These cars are sensitive to settings - my Daimler has much livelier and more responsive steering than another V12 I've driven.

 

Peter,
I've got less than 10 miles in this, or any other Jaguar, but I liked the quick and responsive feel of the steering. I will, unfortunately, have to wait until next year to give it a good road test.

Dave

 

Get more shims.

My oldie Jags always had more than four; I am 99.9% certain that six shims is typical.

Cheers
DD

 

Caster in particular contributes to the feel of the steering. More positive caster = a crisper feel and stronger return-to-center.

Cheers
DD

 

Hmm.
Nix came with 3 shims on each side, the XJS crossmember I just put under it came with 4 shims on each side.
(';')

 

The shims on the top ball joint pemit the correct caster to be set up; no argument about that ! However you must thinl (and measure) the width of the old ball joints and the new ones. They may not be the same at all. If the new ones are too slim, extra shims to what you may already have will be required. When I replacede my top and bottom ball joints in the late 80s with the "everlasting" XJ40 items I just put the shims back as I found them. Maybe the camber was then slightly out, but to be honest, I never noticed any difference in the handling of the car

 

Doug, Elinor, and Fraser,
You guys are killing me! I thought I had just finished with the two and a half day alignment.

OK, the thought did cross my mind for a brief second that adding another shim to the front would tilt the spindle back a little more. But then I said, the ball joint is already against the rear of the control arm mating surface, there is no way it can go farther than that. My upper arms had 2 shims on each side. Doug, on paper I can agree that more shims will allow more adjustment, but the "pocket" created by the outer ends of the control arm halves is defined very closely by the positions of the inner arm attachments to the cross-piece. If you start adding more shims and spreading the outer "pocket" beyond its natural width, the inner bushes would go away very quickly and you would have alignment and stress problems on both ends......I'm thinking. I just finished setting the caster/camber about an hour ago and ventured through the subdivision a couple of times and the steering felt very nice with just the right amount of feed-back. I ended up nicely at:
CASTER: 2.3*P left and right
CAMBER: .5*N left and right
I'll set the TOE tomorrow, or whenever I heal up a little. I'm going to aim for 1/16" IN.

Dave

 

I spent the afternoon driving a rake (I do my best thinking while raking) and thinking about these very questions.
How would one force more in shims without doing some kind of damage to the bushings, I wondered.
Then I read Fraser's post and it's all clear to me. I'm thinking these cars were truly hand built and shims were added at the factory as needed.

There wasn't room for more shims in either of the crossmembers I have dealt with so I put back what I found.

Congrats on a successful First Drive, Dave, even if it was only in the neighborhood.
Ya gotta start somewhere.
(';')

 

Finished the 3-day alignment this afternoon. 3 days you say? Yup, only because I really kept after it. Toe-in set to 1/32" each side, 1/16" total.

Front end and bonnet are next. Hopefully the seat covers will be here by then. Pic.

Dave

 

You alignment numbers for caster and camber and toe are perfect. Congrats.

 

Thanks Greg, hence the 3 days spent (only 3-4 hours/day, old joints didn't appreciate the task), but I'm happy with the end product.

Dave

 

I have heard and read about this String Method of alignment, read that some high profile racers only do theirs this way, but I've never been able to make it work myself. (Hence Nix's trip to the Hot Rod Shop.)

Congrats!!
(';')