IRS

[Jim Beresford]

I am in the processes of a frame off restoration of a 1963 roadster. I have recently completed the frame, suspension and drive train. When we remounted the body on the frame using the exact shim required during original production the car sits about 1 1/2" low on the left side (measured at the wheel well) and I don't know why.
New items:
Trailing arms
Differential support cross member and bushings
Leaf spring
And many other small parts.

Measuring from the back end of the trailing arm to the frame there is 1 1/8" difference and I don't know why. Could the new spring unbalanced?

I am looking for any suggestions of what may be wrong.

When I purchased this car I don't remember this condition existing.
Thanks Jim

jimskiboat@comcast.net

[Joe L.]

Re: IRS

Jim-----

I'll bet that when you got the car it was just the way you find it now except that you didn't notice it. This condition is VERY common in Corvettes and I can tell you from personal experience that it likely was this way as it rolled out the doors at St. Louis. My 1969 was like this when new. I complained about it when new and, finally, a zone representative came out, measured the car at several points and said that everything was within factory tolerance specifications.

I don't know what causes this problem, but I've always assumed that it related to body mounting on the frame. However, other factors might be at play, too. Nothing is related to the suspension, though. I'll bet that if you measure the suspension interrelationship dimensions you will find them near perfect as they were on my car. Believe me, this problem has ABSOLUTELY NOYTHING to do with the spring. I "went down that road of thinking once-upon-a-time" and found it to be a big waste of time and effort.

I ABSOLUTELY DO NOT RECOMMEND that you attempt to correct the problem by revising the shim count. To do so will likely create a host of NEW problems, including the possibility of cracking the body. At this stage of the car's life, the body has taken a set to the frame and the body is not nearly as "supple" and compliant as it once was.

[Chuck R.]

Re: Hey Joe, I can relate to that last sentence *NM*

[Joe R.]

Re: Hey Joe, I can relate to that last sentence

Jim,

I totally agree with Joe that Corvettes did not measure the same at four corners from the factory.

Did you say that measured from the bottom of the frame to the trailing arm was 1 1/8" difference from side to side?

If that is true, I would try the old spring back in the 63 just to check and make sure that the new spring is OK.

If I understand the above correctly, the car is not level from side to side by 1 1/2" and "should" dip in the front on the opposing side.

Check out these things and please get back to us on this as 1/2" to 3/4" is really common but 1 1/2" is not so common and should be very visible to the eye.

Regards,

JR

[Terry F.]

Re: IRS

Maybe you have, maybe you haven't but measure from the tops of the fenders down to the wheel well lips. See how far off the fenders are that way. I you have a fender way off, look at it closely to see if it was replaced in the past.

As far as the frame goes, it can be twisted and cause some of the problems.

Let us know how many shims are in what positions.

Terry

[Gene M.]

Re: IRS

Jim
Were you sure to tighten the four rear leaf spring bolts under the rear end with the weight of the car sitting on it? Try to draw the bolts in a balanced x pattern to insure the load is equal on both half of the leaf spring. Also the castle nuts at the end of the spring will allow for a little adjustment but not much. Gotta bounce the car around up the road to get everything to seat.

[Mike McKown]

You've have some good suggestions.

I don't know the tolerences on the FRAME but I can tell you from proffesional experience, if the FRAME is not dead on (even though it is to spec) it will cause problems like what you are seeing. A milameter here or there and a degreee here or there plus the fact that a frame will twist one way easier that the other (due to assembly welding stresses) can account to your problem.

You can straighten up your car by using a doughnut under your front coil springs (you determine which) and using adjustable links at your rear spring.

AS far as the body shimming, if your door fits are good, you can remove a shim (same size) from each mount, front to rear, without any problem, on the same side to lower the body on that side. I don't think though that you can remove enough shims to help your problem. I wouldn't try to use the body shims to straighten your car out.

[Wayne W.]

Re: You've have some good suggestions.

I have watched this thread for a while now. Lots of good suggestions, but while it is true that some difference is normal, 1 1/2 inches is not. He doesnt say whether he serviced the front suspension or not, but if he did, my guess is that he has the front springs in wrong. If one is ont up into the shock tower correctly it will cause exactly the same symptom. Other than that the first thing to do is to jack the car up and set it on four equal stands mounted under the center box frame. This box should be square and level. Then measure all of the frame points to the ground plane. And all of the body points to the same plane. This will tell you instantly if the problem lies in the frame, body, or suspension.