INSTALLING TRAILING ARM SHIMS

[Rob A.]

I have seen several questions in the archives regarding re-installing trailing arms when the original shim packing is not known. I find myself in that same position. Here is what has been suggested to me by the shop that rebuilt my trailing arms; With just the pivot bolt in place, (no spring or strut attached) start with a 1/4" shim on each side, then pack the remainder, keeping the rotor even with the outside of the frame rail.

[Chuck G.]

Re: INSTALLING TRAILING ARM SHIMS

I guess that's as good as any suggestion. There are variations in the frame, which might not allow for even shim placement. Whatever you end up doing, after the car is done and back on the road, you're going to need a 4 wheel alignment anyway. I had the T arms out of my 69 last winter. Found one bent arm which needed replaced. When I put the shims back in, I used the same number of shims on the replaced T arm side as were on the original T arm side. Worked out for me. When I took the car to the alignment shop, it was within spec. Somebody smarter than me can probably tell you how to "string" the car to set the rear toe-in. Chuck

[Michael W.]

Re: INSTALLING TRAILING ARM SHIMS

Your best bet and the most conventional wisdom is to simply put half the shim pack on one side and half on the other side of the trailing arm - to start with. This will bring you within one or two degrees of the desired range on a typical car.

This is MORE than accurate enough to get you to the alignment shop.

[Harmon C.]

Re: INSTALLING TRAILING ARM SHIMS

Mike Any of the above methods will get you to the alignment shop but finding someone willing to take the time to adjust the shims and do a good job can be a problem. I pay by the hour to a older Corvette guy who uses an old machine and like the results.

[Joe L.]

Re: INSTALLING TRAILING ARM SHIMS

Rob-----

The methods suggested by the others are right on. To synopsize:

1) If you have a situation where you disassemble the suspension and know the shim packs on either side of the bushings, use the same shim packs when you reinstall, regardless of other changed parts;

2) If, for whatever reason, you don't know what the original shim packs were, then place half the total shim pack thickness on either side of the bushings.

Also, NEVER, EVER use the original 64-69 style "two-hole" shims. ALWAYS use the 70+ style "SLOTTED-ON-ONE-END" shims. You don't need to use the cotter pins with the later syle shims used on earlier cars IF you install the shims properly AND are certain that you have a TIGHT shim pack (like you should for other reasons).

[Juliet P.]

Re: INSTALLING TRAILING ARM SHIMS

Joe wrote "Also, NEVER, EVER use the original 64-69 style "two-hole" shims. ALWAYS use the 70+ style "SLOTTED-ON-ONE-END" shims."

Joe, other than the hassle to align the car issue, is there another reason you state this? It's very rare for you to use the NEVER, EVER statement. FWIW, my early '70, Feb 18 build date had the two-hole shims. When I redid the rear suspension I put in shims just like the originals. It required pulling the T-arm pin on one side to get the rear aligned, which cost a bit more, but worked out fine. Thanks, ~Juliet




1970 Corvette Registry

[Joe L.]

Re: INSTALLING TRAILING ARM SHIMS

Juliet-----

The difficulty which is created for alignment is the entire reason that I suggest NEVER, EVER using the "2 hole" shims.

Removing and reinstalling the forward pivot bolt which is required to replace/change "2 hole" shims can be a nightmare. In fact, this is usually one of the most difficult parts of trailing arm removal/installation on the car. So, having to do this, perhaps several times, during the course of an alignment can be frustrating and expensive. Most shops will only do Corvette rear alignments on a "per hour" basis; no flat rate. This is the reason.

What's more, there is another "hidden negative" to using the "2 hole" shims: having experienced the "pain" of removal and reinstallation of the bolts and realizing that the customer's bill is rapidly escalating (which will not make the customer happy when the customer finds out that the rear alignment is going to cost several hunder dollars), the technicians become inclined to be satisfied with "it's close enough".

When you think about it, all of this pain, misery, frustration, and expense over the use of "2 hole" shims which feature is virtually indiscernable with the shims mounted on the car. In my mind, it's just not a wise restoration decision. Many negatives and only 1 theoretical positive. Personally, I would NEVER, EVER use the "2 hole" shims. Under no circumstances. EVER. PERIOD.

[John D.]

Re: INSTALLING TRAILING ARM SHIMS

Joe:

I just pulled my trailing arms to have them rebuilt. I kept the 2 hole shims (early 68) in zip lock bags to reuse them. The question is, in your opinion should I reuse the old rusty ones or acquire new ones? I am concerned about the thinning of shim x-section due to steel oxidation and flaking.

I believe there were standard thicknesses for the shims so it ought to be a staight forward replacement.

I am leaning toward replacing with the two hole shims, or possibly "hiding" the slotted ones inside the two hole ones.

Any thoughts are greatly appreciated.

John

[Craig S.]

Re: INSTALLING TRAILING ARM SHIMS

John - I got a set of two hole shims from LI corvette. I am thinking of using them on the outside and using the slotted shims inside to allow easy adjustment. They don't show much anyway if you don't install the cotter pin. Joe L. had recent posts about never using the two hole style.......Craig

[Roberto L.]

Re: INSTALLING TRAILING ARM SHIMS

Hello, get a new set of slot like shims. Sets usually come in three or four diff thicknesses. As Joe said many times, ones installed nobody will know the difference.
In my 70 the right side was more problematic to install due to lack of space, but if I'm correct 68 doesn't have the chassis side reinforces, so installing the bolts are a lot easier.

good luck, Roberto, NCRS #30019, RMC