C2 trailing arm shims

[Steve D.]

It seems that if the shims come out unexpectedly at moderate to high speed, dire consequences would follow. I am assuming that this is a very rare occurrence, but are there any precautions to take other than proper assembly (ie tapping in last shim and torqueing and keying the bolt)?

Steve

[John H.]

Re: C2 trailing arm shims

The consequences aren't necessarily dire, but it does make a hell of a racket when they fall out, bounce off the road and back up under the car, and you can see them in the mirror as they flash in the sun while bouncing behind you; don't ask how I know this Things just get a little squirrelly when you accelerate, brake, or turn - there's no question when you've lost them and the front of the trailing arm slides back and forth laterally on the bolt. Probably the best precaution to take when using the slotted shims is to drill the frame and use the long C3 cotter pins through the holes in the shims to retain them. There are other ways to retain them, but I think the cotter pin approach is the most sanitary.

[Duke W.]

Re: C2 trailing arm shims

If the shim packs are properly configured and installed, they should not come out. Use 1/32" shims in each of the four packs as necessary so that the last shim is a slight interference fit. Then remove the thickest shim, put the last 1/32" shim in place and tap in the thickest shim.

Now with the suspension at normal ride height, torque the trailing arm bolt to spec. My SWC does not have the captured or cotter pinned shims, and I never lost one.

Duke

[Steve D.]

Re: C2 trailing arm shims

I have the body off of my 63 convertible, and am reassembling the chassis. I marked the shims as they were removed during the tear down, and have now cleaned up and reinstalled the same shims. Putting in the last shim on each side required more than tapping. More like pounding. It is probable that the prior configuration was not proper. Maybe I should start from scratch following your instructions for shimming?

Steve

[Duke W.]

Re: C2 trailing arm shims

If you installed new trailing arm bushings, the shim pack may not end up
the same as original, but the original shim configuration is a good place to start. Maybe you should remove one 1/32" shim on the packs, then make new measurements to ensure that your toe-in is correct.

I recall when I did my SWC (frame off) that on at least one side one 1/32" shim
ended up on the other side of the trailing arm to get the 1/32" toe per wheel
that I was shooting for, but the total shim
count was the same as what I took out. I essentially used all the original
shims (that had been cleaned up and replated), no more, no less, but the final
positions were not quite the same, and the packs were tight with the final
(thick shim) requiring tapping with a hammer to install due to a slight interference fit.

I measured the toe-in on each side from a string that I carefully hung along the centerline of the frame with plumb bobs with the rear suspension blocked up (spring not connected) to the nominal "D" dimension, which is nominal normal ride height. To find the centerline I carefully measured the center points at each cross member and recall that they lined up quite well.

Duke

[Dick G.]

Re: C2 trailing arm shims

The shim kit I have is a non-slotted pack of shims. From your posts, I presume they were to be slotted. Both ends? So now I suppose I need to order a new slotted kit? Although, using non-slotted shims would stop any from falling out,it would make any adjustment more difficult. Any suggestions appreciated.

[Joe L.]

Re: C2 trailing arm shims

Dick-----

1963 used unique-to-that-year slotted shims. For 1963, no additional retention method for the shims was used.

1964 to ABOUT 1970 used shims with holes on either end. These shims make rear toe adjustment extremely difficult and I absolutelky DON'T RECOMMEND the use of these shims for ANY 64 to 70 Corvette.

From ABOUT 1970 through 1982, the shims were slotted on the inner end and had oblong holes on the outer end. These shims were used with special long cotter pins that went through holes in the frame and the outer holes in the shims to provide "positive" retention of the shims. I don't think that the cotter pins are absolutely necessary if the shims are installed TIGHT and are oriented down into the frame cavity (as they have to be, anyway, if the cotter pins are to work as designed). The key factors are: (1) the shim pack has to be TIGHT, with the last shim pounded in as previously described; (2) the shims have to be oriented so that they are facing downward into the frame cavity for additional retention; (3) the forward torque arm bolt has to be torqued to specification (with the car sitting at NORMALIZED ride height) and the cotter pin properly installed.

I recommend the use of the ABOUT 1970 through 1982 style shims (inner slotted)for ALL 1964-82 Corvettes and I also recommend them for 63's if you don't have the original 63-style shims.

[Joe L.]

Re: C2 trailing arm shims

Duke-----

If the trailing arm bushings are installed correctly using GM parts, the final installed "thickness" of the forward bushing assembly (as measured from the face of one bushing washer to the other) will be the same as original. This is especially true if the bushing washers are re-used as they often can be. Even if new GM washers are used, it won't make any real difference; I've measured the thickness of original versus current GM washers and they are the same to within a few thousandths. When I did the bushings on my 69, I measured the total thickness before and after. They were the same within a few thousandths. Actually, I was surprised that they ended up this close, but after thinking about it, if the installation is done properly and parts of the original dimensions are used, it ought to come out just about the same. And, it did!

If the frame cavity into which the trailing arms attach is not distorted (as can happen if the previously installed shim pack was not TIGHT when the forward bolt was tightened OR if too much force was applied to install the final shim), then the TOTAL shim pack removed will be exactly the same as the TOTAL shim pack installed. Of course, there may need to be an exchange of shims on either side of the bushing to achieve proper toe, but the total will be the same before and after.

[Eugene B.]

Re: Stainless steel shims

Gents,
I will be putting my '65 back together with original style (two hole) shims. I did choose stainless steel to eliminate rusting and make future removal for alignment purposes easier.

Question: Do judges use a magnet to determine if SS steel shims have been used and if so, what is the point deduction for using same?

Thanks,
Gene

[Joe L.]

Re: Stainless steel shims

Gene-----

I don't know if the judges subject the shims to the "magnet test". I expect they do, but it's not too hard to discern the "stainless steel look", anyway. I have no idea of the points loss. I would NEVER use anything but stainless steel shims. Even here in California, the unplated, mild steel shims rust rapidly given their location. Rusted originals aren't "original", either, with respect to condition.

Do as you wish regarding the 2 hole shims. Personally, I wouldn't even CONSIDER using them. It will cost you big $$$$ to get the rear aligned since most shops charge by the hour for Corvette rear alignments, not flat rate. In any event, you're unlikley to get as good of an alignment job with these shims installed. The technician will be VERY inclined to say (to himself) "that's close enough".