Question: 1986 Caster Alignment Question

[chris123]

It seems to be getting harder and harder to find a qualified shop that knows what they are doing in regards to performing a 4 wheel Corvette alignment, especially in my area. Anyway, I bought it to Steve Shannon Tires in my area, and they did a 4 wheel alignment; they were able to get the front and rear toe dead on, as well as the front and rear camber, however they say they don't really mess around around with the Caster settings (only adjustable in the front on the Corvettes); I though that was part of an alignment? The settings for the caster came up as follows:

Left - +4.0 Right - +4.3

The FSM calls for +6 plus or minus .5; my question is are my numbers close enough not to even have someone mess around with it? It doesn't seem to pull or wander when driving down the road. I've read that the Caster numbers should be as close as possible to each other, even if they are not in spec. They seem to want to charge me additional labor to bring it back to set the Caster, and they said it could result in the car pulling or wandering to one side. What happened to having a little confidence in your technicians? Anyway, before I bring it to another shop (Jack Williams Tires), should I just leave well enough alone since the current settings are not too far off. Not sure I can even find a place that specializes Corvettes here in Northeast PA..........

Regards, Chris

 

[vigman]

.3 diff side to side

I do not believe that will be an issue.. and " The FSM calls for +6 plus or minus .5 " 2 degrees off MEH, your in the groove...
If you really want to get pickey... how much fuel was in the car, how are the bushings & ball joints, when was their rack last serviced, how much play are in your tie rod ends & front wheel bearings and rear bearings?.. How true are your rims.... All this comes into play...

The bottom line, does the car pull? are the tires inflated properly?...
Most of all keep your eyes on the wear pattern....

Mike

 

[chris123]

I do not believe that will be an issue.. and " The FSM calls for +6 plus or minus .5 " 2 degrees off MEH, your in the groove...
If you really want to get pickey... how much fuel was in the car, how are the bushings & ball joints, when was their rack last serviced, how much play are in your tie rod ends & front wheel bearings and rear bearings?.. How true are your rims.... All this comes into play...

The bottom line, does the car pull? are the tires inflated properly?...
Most of all keep your eyes on the wear pattern....

Mike

Vig: Thanks for the reply; that's what I kinda figured; all of the suspension components are in surprisingly in good shape; tech said only the slightest/tiny bit of movement in the left inner tie rod, but nothing that needed to be replaced right away; full tank of gas as per FSM, although I do have the exhaust system removed from the (main) cat back, so that probably changes things by about 40 pounds or so; tires are at 32 psi, and it seems to track pretty straight so far, although I haven't gone on any highway rides yet; car doesn't seem to pull either way so far, so I should probably be all set; just wanted to get a couple of additional opinions..........

 

[Hot Rod Roy]

That's a rather wierd answer from your alignment guy. The camber adjustments and the caster adjustments use exactly the same shims! These shims must be selected carefully to get both the camber and the caster within specs. Sounds to me like someone is getting lazy, and not wanting to spend the time to get both the camber and the caster right! It does take some time to get them both within spec, because one adjustment affects the other. They probably do this all the time, because most people can't read the spec sheet, and can't tell the difference in how the car drives. Your reduced caster will cause the steering to not return to straight-ahead quite as easily, but isn't so bad that it will cause the car to wander. With the camber correct and the caster at 4*, tire wear will be okay.

 

[Hib Halverson]

First...find yourself another alighnment shop. Any place that charges extra to set the caster is out to screw you. With a Corvette a "four-wheel alignment is front camber, caster and toe and rear camber and toe adjustments done to the service manual specs.

As for your about 4° caster rather than the FSM-required 6° or so, instruct your new alignment shop to set camber and toe to factory specs and if they can't get the factory caster number then I'd start looking for problems with the chassis/suspension such as: prior collision damage, suspension damage due to curb hits or etc, worn parts, wrong parts or anything which would prevent a factory caster adjustment once the factory camber adjustment is set.

 

[Hot Rod Roy]

Chris, take a look at the two bolts in each of your upper "A" Arms. Do the rear bolts have zero shims? To get more caster, these bolts need to have fewer shims, so if they already have zero shims, you've got a "challenge". Notice that there are large spacers on these two bolts, which are two different lengths. Do your rear bolts have the long spacers? If so, you're in good shape. Alignment shops will sometimes only add or remove shims, and don't like to remove bolts, but by trading the long and short spacers, you can get the adjustability you need.
Remove your front wheels, then remove the nuts on these bolts, Accurately measure the length of the spacer and shim pack on each bolt. Put the short spacer on the rear bolt, then add the appropriate number of shims to match the original measurement for that bolt. Put the long spacer on the front bolt and the spacers to match the original measurement of the front bolt. This should give you exactly the same caster and camber you had from the tire shop.
Take your car back to the tire shop, and they should be able to repair your car with the correct caster and camber at no charge, or give you a partial refund for their partial job! No excuses! Good luck!

 

[Hot Rod Roy]

Chris, it's been over a month since you posted your question. Several members tried their best to help you. We're all wondering what you decided to do. This forum works the best when we all share the information we've learned from our experiences. What did you learn? Do you have anything you can share with the many, many people who have read this thread?