Thoughts on front-end alignment?
I just replaced my upper & lower ball joints, steering rack (newer face-lift version), outer tie rods, and polyurethane bushings for the control arms, sway bar, and steering rack.

According to Jag-Lovers the alignment specs with 205/70/15 tires are as follows:
Castor angle: Positive 3.5 degrees (+/- .25 degrees)
Camber angle: Positive .5 degrees (+/- .25 degrees)
Alignment: Toe Out 0 to 1.6mm (Pre-HE) -OR- Toe-In 0 to 1.6mm (HE)
[xj-s] Alignment Specs

My application:

• 1978 XJ-S
• Small Block Chevy
• Later model face-lift steering rack
• Polyurethane bushings
• 245/50/17 Tires on XK8 wheels - currently no spacers, does not appear to be any rubbing
• Street driver but 'may' hit a road track that's not far from us from time-to-time.

I understand camber is via the upper control arm shaft shims and caster is via the four upper ball joint shims - local recommended independent alignment shop apparently understands this also.
Both upper ball joints have the four shims each for the caster and I already have a bag of 1/32 slotted shims for camber to make life easy.

Thoughts?

1. Use the specs as shown above from Jag-Lovers or any recommended adjustments?
2. Does the 245/50/17 wheel/tire change have an impact?
3. Toe: figured I'd go 0 to meet in the middle between Pre-HE and HE?

Thanks,
Steve

 

From your post:
Toe out is a mistake. The factory spec is 0 to 1mm toe in. I find 0.5mm is best. This toe-out error derives from a typo in the Haynes manual.
Your castor is correct.
Camber angle is not correct, it should be 0.5 degrees negative.

On the rear, by removing shims in the driveshaft/diff flange joint you can get about 0.5 degrees negative camber. This greatly improves the cornering and general handling of the car and I strongly recommend it. Up to 0.75 degrees is fine.
Good luck with the car

 

@Greg in France Thanks again for some insight; going to the alignment shop this Friday morning and then for a new exhaust afterwards.

 

Remember to explain to the garage that:
Front Castor is adjusted by moving the shims (front to back or vice versa) between the top ball joint and the outer ends of the top wishbone. The INNER fulcrum must NOT be changed in the castor adjustment.
Front camber is very unlikely to need adjusting unless the subframe has been whacked. If it does need doing, I strongly advise yopu to post again before you let the garage adjust it. The adjustment involves unbolting the top wishbone fulcrum pin and adding or subtracting shims between the fulcrum pin and the subframe. The SAME thickness of shims must be at both ends of the fulcrum. This is not an easy adjustment to make as the bolts holding the fulcrum pin to the subframe are not easy to undo when they have been untouched for 30 or more years.
Finally, the rack MUST be centralised to adjust the toe, and each side adjusted separately using its own tie rod/ball joint adjustment.
I only mention this because some garages think doing all the adjustment at one end of the rack is OK - it is not! If the rack is not centralised the power steering will be trying to turn the wheels from the straight ahead.
In this diagram the castor shims are number 11, the camber fulcrum pin number 3, and the camber adjustment shims number 14.
https://parts.jaguarlandroverclassic.../brand/jaguar/

 

Thanks again @Greg in France
Heading to the alignment shop tomorrow morning; over the phone I verified that they are familiar w/ the Jag setup and adjusting caster via the four shims on the upper ball joint - they are familiar, I also plan on being there while they do the alignment.

I'll remind them to ensure camber shims to remain equal between fore and aft.

I had also planned on bringing up to center the rack first for toe adjustment to ensure the rack is centralized and then adjust each side as necessary via the tie rod ends (I even typed up a sheet w/ the settings and a pic showing the bolt to remove for rack centering) - I'm not at all worried about the steering wheel being centered as I just rec'd my new steering wheel and plan on installing it on Saturday and will center the wheel at that point.

It's not terrible driving right but it does obviously need an alignment. I did notice a HUGE improvement in stability and less sway with the polyurethane bushings all around along w/ the 17" alloy wheels with 50 series tires as opposed the previous 15" wire wheels w/ 70 series tires - excited to get the alignment done and then hopefully a new exhaust afterwards tomorrow afternoon.

Thanks again, Steve

 

Interesting you should say that about the larger wheels, as usually the reports are with 15" wheel and taller tires the car can be a "hands off the wheel and glides down the road in a straight line" type performance, while with large wheels and low profile tires it turns into a tramlining beast that twitches at the slightest imperfection in the road surface and is a white knuckle experience to hold the car in a lane.

 

XJS on a track???? Sounds like fun... If you don't care about tire wear you could increase the camber to over 1.5 degrees. There might space to add a thick washer on the upper control arm that pull the upper ball join in. For the rear you can take out the drive shaft spacers for more camber. More camber will make a huge difference in road holding at the limits at the expense of wire wear. With more camber you MIGHT get some on center squirm depending how your tires are constructed and how far you go with the camber.

You need to have some front toe in. It makes no difference at the limits but some toe in takes up linkage lash and makes for good on center feel.
Keep in mind 1/16 toe in measured at the wheel rim is different on a 15 inch wheel compared to a 17 inch wheel. Make sure the alignment machine knows the new rim size. Some machines convert the value in to degrees which is universal. Generally speaking you need more toe in the more camber you add to tame squirm but every car / tire / wheel combo is diffrent. So much so that many new cars come with tires designed specifically for the car.

For the ultimate experience and involvement I've learned to do my own alignment at home using string. The reason is performance tires vary greatly. One might feel great with 1/16 toe in and another might not.