C3 Rear Wheel Alignment

[Kevin Morris]

Hello all. Hope everybody is planning on a nice weekend, I know I am! The rear wheels on my '72 seem to be out of alignment. What I mean by this is, they seem to track straight, but if you look at the car from the rear, the tops of the rear tires/wheels seem to be in more than the bottom (the part of the tires that are touching the pavement). Looking from the rear of the car, the tires look like this..... / . So, I don't know if it needs an alignment or what. Reportedly, the previous owner had totally rebuilt the rear end of the car, new SS calipers, brake lines, u-joints, bearings, spring, shocks, etc. So, I don't think it would be the bearings...and I have heard no noises from the rear bearings, either. Could adjusting (tightening upward) the nuts on the ends of the two bolts that come down through either end of the leaf spring be a fix??

Kevin #39927

[Patrick H.]

Re: C3 Rear Wheel Alignment

First of all, check the bushings of your rear strut rods (the ones that run along your rear spring). If they're OK, then you need a simple alignment.

The "quick and easy" way to do this is to lift the rear of the car, and adjust the bolt holding the inboard end of the strut rod so tht the rod is moved inward. Drop the car down, and move it back and forward about 20 feet each way. Use a level, and see if the top of the trim ring is now tilted in about 1/4 to 1/8 inch from plumb when compared to the bottom of the trim ring (or edge of the rim if you remove the ring). You may have to adjust the rods in or out to get close, and it may take a try or two. Once you're about 1/8"+ from plumb, you're darn near right on.

I've done this and had it checked, and been VERY close.

Patrick

[Shannon Burgess]

Re: C3 Rear Wheel Alignment

What Patrick says is correct, first check the rear strut rod bushings and the camber adjustment cams directly below the differential. If the bushings appear in good condition and you still cannot get an acceptable camber setting, you may be looking at a larger problem.

The upper "link" of the rear suspension is established by the halfshaft. The side yokes in the differential will wear on their ends, effectively reducing the length of the upper link in the suspension. This will cause excessive negative camber as you have described. If the side yokes are worn down appreciably, then you will not be able to get the rear aligned without replacing the yokes.

To check the yokes for wear, raise the rear end and place jack stands under the frame forward of the rear wheels. Use your jack to take a little pressure off the leaf spring on one side by slightly jacking up on the end of the bottom leaf. Then grab the tire at 12:00 and 6:00 and lift up on the bottom while lifting up and in on the top of the tire. Watch the side yoke in the differential to see how much play is present. If it's 1/8" or more you've found the dreaded cause.

Shannon

[Duke W.]

Re: C3 Rear Wheel Alignment

What you are seeing is "negative camber", which your car should have. You can buy an inclinometer at a hardware store, measure it yourself, and compare it to the range of accepatble specs in your service manual or AIM.

Beyond this if the tires don't show an odd wear pattern, the alignment is probably okay. Rear tires will normally wear a bit more on the center or inside center and front tires tend to wear the shoulders.

Tire rotation will even this out over the life of the tires.

Duke

[Patrick H.]

Re: C3 Rear Wheel Alignment

Duke,

FWIW, I found the method I descibed above with the level to be quite accurate, and as most people have one (but not an inclinometer) it involved the purchase of no new tools.

Not that new tools are a BAD thing.

Patrick

[Terry M.]

Re: C3 Rear Wheel Alignment *TL*

All the above information is right on the money. A thorough inspection of the rear suspension is in order. I think deterioration of the bushings at the outer end of the rear spring will contribute to negative camber also.
While all these posters are correct the original specification for your 1972 calls for a slight amount of negative camber, later C3 specifications (once radial tires were used on the cars) called for zero rear camber. If you are using radial tires, I suggest adjusting closer to zero negative camber. The car will handle better, if that is your set up.
I sure hope you don't find the dreaded yoke wear, it will not help your weekend if you do. I found it on my car last fall, and it didn't do much for my day.

[Kevin Morris]

Re: C3 Rear Wheel Alignment

AIM ?

[Kevin Morris]

Re: C3 Rear Wheel Alignment

Terry, I take it that this yoke wear problem is an expensive fix? What is involved?

Kevin

[Craig S.]

Re: C3 Rear Wheel Alignment

Assembly Instruction Manual. You can order for your year here on this website..Craig

[Craig S.]

Re: C3 Rear Wheel Alignment

Kevin - this requires removal of the 3rd member by removing rear spring, disconnecting halfshafts,driveshaft, and dropping the differential. Then remomve the differential carrier from the 3rd member, and the rear cover. Then the rear end can be rebuilt with new posi clutch packs and stub yokes. If you are not experienced or comfortable with setting up rear end gear patterns and shimming posipacks, send it to someone reputable such as Bairs in Linesville PA or Van Steel in Florida...Craig

[Patrick H.]

Re: C3 Rear Wheel Alignment

Terry,

It shouldn't bother cars that aren't driven, though.

Patrick

[Kevin Morris]

Re: C3 Rear Wheel Alignment

Heeeey, who doesn't drive their car?!

Kevin

[Kevin Morris]

Me Driving My Car!

http://community.webshots.com/scripts/editPhotos.fcgi?action=showMyPhoto&albumID=77367472&photoID=87994061&security=wbMYtE

[Terry M.]

Re: C3 Rear Wheel Alignment *TL*

Kevin,
That was Patrick's dig at me. I pretty much don't drive my car any more. Patrick drove one of his from Michigan to Pittsburgh for their Regional, back to Michigan, and then the Harrisburg for the National Convention this summer. He was trying to make an "inside" comment, and I have now "outed" him.

When you have been around here a while you will know about these kinds of shots. Most folks don't take them too seriously. We are a tough bunch, but friendly. It is all in good fun.

The differential yoke job can be a little less complex than described. The third member will come out the front, and the cover, spring and strut rods can be left in the car. Half shafts and spring outer ends do have to come loose. Replacing the yokes, and setting up the differential is not a job for the armature, however. And once out, one might as well replace the bearings and rebuild the positraction. There are lots of expensive parts in a very small space back there. Hope and pray that worn differential yokes are not your problem.

[Patrick H.]

Re: C3 Rear Wheel Alignment

Terry,

I knew you'd get it.

Actually, I plan on removing the rear differential in my blue 71 this winter, and having it rebuilt. It's got on more than twice the mileage of the yellow 72, and it's past time. And, having done it on my Dad's 72, I know very well what a job it will be.

We ought to get you to buy a lightly used C5 and have fun with a Corvette again.

Patrick