C2 trailing arm shims

[Frank D.]

Re: C2 trailing arm shims

NCRS restoration standardsfor the mid year trail arm shim is the longer two hole shim. A slotted configuration is wrong as in not typical factory production and will be a deduction under the CDCIF standards as total wrong configuration and receive a full deduction.

There is a reason GM made the design with holes and not an open slot. The shim is 100% captive and no chance of dislodging over the life of the car even under extreme conditions, rust, degradation, and wear. Just because a slotted design is easier doen’t justify it as a viable option.

It does in my book - I'll take a points hit to have an easier job of aligning the car...

[David H.]

Re: C2 trailing arm shims

It does in my book - I'll take a points hit to have an easier job of aligning the car...

Frank,

Agree. Shims are included in Chassis: Trailing Arm Assemblies & Spindle Support -- 5 points Originality, 5 points Condition. After assessing point fraction assigned to Shims alone, then assessing partial deductions for issues of Configuration, Date, and Installation with those shims, total points lost is minimal.

Dave

[Joe L.]

Re: C2 trailing arm shims

Gene-------


If someone is building a car to be, essentially, a "trailer queen", by all means use the original shims. In fact, for such a car a rear alignment is not even necessary-----just place half the shim pack on either side of the bushing and be done with it.

However, if someone is actually going to drive the car, then I highly recommend using the slotted style shims. In fact, GM replaced the original 1963-69 "2 hole" shims with the slotted style for 1963-69 SERVICE. So, apparently, GM approves the use of the slotted style shims for 1963-69 Corvettes. Otherwise, they would simply have discontinued the "2 hole" shims without supersession.

If someone wishes to maintain the original 1964-69 shim installation configuration as installed on the car, one only needs to slot the original shims by removing the material between one of the holes and the end of the shim thus making it slotted. Once installed, no one will be able to discern the difference. As I previously mentioned, I used the slotted shims not installed down into the frame pocket and without cotter pin for many years and miles and never had a problem. Apparently, GM came to this conclusion or they would not have replaced the "2 hole" shims with the slotted style for SERVICE of 1963-69 Corvettes. Also, consider this: the front a-arm shims have always been of the slotted type and have never included any sort of "fail safe" retention mechanism. I've never heard of one falling out. Certainly, it's never happened to me on any Chevrolet model I've owned.

When it comes to strict adherence of originality, as I've said before there are many deviations from this on even the most correct and meticulous restoration. No Corvette was ever supplied with stainless steel sleeved calipers, wheel cylinders, or master cylinder. Anyone that uses original connecting rods with 1962-65 327's is asking for trouble. Etc., etc., etc. And, as Dr. Rebuild so accurately states, "any part that is not original to the car is a replacement part". That's true even of NOS parts.

Others may differ, but for me restoration is not a religion. While I certainly like and appreciate original configuration, I'll deviate from it when it makes sense and the deviation is either unseen or an insignificant compromise of original configuration.

[Timothy N.]

Re: C2 trailing arm shims

I’ll just add what I did if it has any value for consideration. I aligned mine myself by putting the car on 4 ramps so car sat on its weight but I could get under it. Let the tires set on plastic bags so I could bounce the car and it would relax to its normal stance. The camber caster heads I have fit the rear hubs with wheels on and adjusted the camber. I then used the open shims and started to adjust the toe in and tracking on the trailing arms. I used a string to run across the rear tire up to a data point half way up the frame. I made sure the distance was equal on both sides to center of the frame and also moved the trailering arms with the OPEN shims until I got the correct toe in and centering (no dog tracking) . After I rechecked camber, I then removed the open shims and replace them with the exact correct closed shims. Then I again made sure all was correct spec wise. Time consuming (a day) but I knew when I locked it down they would never need to be redone and I had the original shims for judging. Just explaining what I did...PS Just a tip I learned after getting red faced under the car, when reinstalling the trailing arm bolt, use a center punch to line up the hole. Reinstall the bolt, you might find that it does not line up on the outside hole. In other words the bolt is half way through and stops. Jack up a little and remove the ramp so the trailing arm can hang. As you lower the arm to the “hang” position, the outer hole lines up with the bolt. After I learned that, the job really became pretty easy changeing the shims back to the originals... Tim

[Gene M.]

Re: C2 trailing arm shims

Gene-------


If someone is building a car to be, essentially, a "trailer queen", by all means use the original shims. In fact, for such a car a rear alignment is not even necessary-----just place half the shim pack on either side of the bushing and be done with it.

However, if someone is actually going to drive the car, then I highly recommend using the slotted style shims. In fact, GM replaced the original 1963-69 "2 hole" shims with the slotted style for 1963-69 SERVICE. So, apparently, GM approves the use of the slotted style shims for 1963-69 Corvettes. Otherwise, they would simply have discontinued the "2 hole" shims without supersession.

If someone wishes to maintain the original 1964-69 shim installation configuration as installed on the car, one only needs to slot the original shims by removing the material between one of the holes and the end of the shim thus making it slotted. Once installed, no one will be able to discern the difference. As I previously mentioned, I used the slotted shims not installed down into the frame pocket and without cotter pin for many years and miles and never had a problem. Apparently, GM came to this conclusion or they would not have replaced the "2 hole" shims with the slotted style for SERVICE of 1963-69 Corvettes. Also, consider this: the front a-arm shims have always been of the slotted type and have never included any sort of "fail safe" retention mechanism. I've never heard of one falling out. Certainly, it's never happened to me on any Chevrolet model I've owned.

When it comes to strict adherence of originality, as I've said before there are many deviations from this on even the most correct and meticulous restoration. No Corvette was ever supplied with stainless steel sleeved calipers, wheel cylinders, or master cylinder. Anyone that uses original connecting rods with 1962-65 327's is asking for trouble. Etc., etc., etc. And, as Dr. Rebuild so accurately states, "any part that is not original to the car is a replacement part". That's true even of NOS parts.

Others may differ, but for me restoration is not a religion. While I certainly like and appreciate original configuration, I'll deviate from it when it makes sense and the deviation is either unseen or an insignificant compromise of original configuration.

Joe
The front A arm shims are a different situation. They are locked up solid between a flat frame member and a forged casting. The trail area are between the frame sides in a pocket against a pivot cushion on both sides. The arm does articulate up and down. It either twist the rubber cushion or the steel washer face sides. This has a definite chance of wear. Excessive bolt tightening will BEND IN THE FRAME SIDES. I have seen plenty of Corvettes at the cruise in with missing shims in the trail arm frame pockets. The owners did confirm the car was squeamish down the road.

You are free to do as you like and take the easy way. But to be correct per CDCIF the judges will now slide in their little mirrors to verify the shim is not cut for slip in assembly. Open slot in is not 100% it definitely has the possibility of dislodging as I have seen and pointed out.

I drive my cars all over the country. In fact 1000’s miles on the ‘65 and the shims are full hole style as GM built and I have no alignment issues. I assembled the shimming as they were and aligned the car. Took the car home made the shim changes as per alignment data re set the car at alignment to verify and all was perfect. A word of advice if you drive your car a lot as I do set the camber at zero to eliminate inside tire wear.

Thank you for your very lengthy response but I have to agree to disagree with your slotted shims. The rest was on service and adherence of originality, and religion seems illrevelent to the shims. What’s that all about?

[Brian M.]

Re: C2 trailing arm shims

So let's hear the point deduction for slotted shims.

[Frank D.]

Re: C2 trailing arm shims

I'd have to dig out my 2016 regional judging sheets to see if they were even "caught"; my car has had slotted shims since I've owned it and when the trailing arms were rebuilt 6 months back I added the long cotter pin to secure them. But I drive my cars - a lot....

[Joe L.]

Re: C2 trailing arm shims

Joe
The front A arm shims are a different situation. They are locked up solid between a flat frame member and a forged casting. The trail area are between the frame sides in a pocket against a pivot cushion on both sides. The arm does articulate up and down. It either twist the rubber cushion or the steel washer face sides. This has a definite chance of wear. Excessive bolt tightening will BEND IN THE FRAME SIDES. I have seen plenty of Corvettes at the cruise in with missing shims in the trail arm frame pockets. The owners did confirm the car was squeamish down the road.

You are free to do as you like and take the easy way. But to be correct per CDCIF the judges will now slide in their little mirrors to verify the shim is not cut for slip in assembly. Open slot in is not 100% it definitely has the possibility of dislodging as I have seen and pointed out.

I drive my cars all over the country. In fact 1000’s miles on the ‘65 and the shims are full hole style as GM built and I have no alignment issues. I assembled the shimming as they were and aligned the car. Took the car home made the shim changes as per alignment data re set the car at alignment to verify and all was perfect. A word of advice if you drive your car a lot as I do set the camber at zero to eliminate inside tire wear.

Thank you for your very lengthy response but I have to agree to disagree with your slotted shims. The rest was on service and adherence of originality, and religion seems illrevelent to the shims. What’s that all about?

Gene------


The trailing arm forward attachment assembly is just as "solid" as the front upper a-arm. The bolt compresses the frame, shims, bushing plates and retainers. This is all just as solid as the front a-arm inner attachments. There is no "rotation" at the trailing arm forward attachment steel components. All of the "rotation" occurs within the flex of the rubber bushing.

There are more definitions of religion than the common one involving a supreme being. Here's one from the dictionary and it's exactly what I was referring to in my previous post:

---a pursuit or interest to which someone ascribes supreme importance

[David H.]

Re: C2 trailing arm shims

So let's hear the point deduction for slotted shims.

Brian

5 originality points total for Trailing Arm Assemby and Shock Mount Bolts. Assign Shims a percentage of that 5 points, then assess damage based on CDCIF. Pretty minor out of 4510.

Dave

[Brian M.]

Re: C2 trailing arm shims

5 points I'd make a notation. This type of kniticking and point deduction is a deterrent to this hobby. JMHO

[David H.]

Re: C2 trailing arm shims

5 points I'd make a notation. This type of kniticking and point deduction is a deterrent to this hobby. JMHO

5 points total for line. Expect shims would get assigned 1 point, then some fraction of 1 point CDCIF of that. Call it 1 point.

[Joe L.]

Re: C2 trailing arm shims

5 points I'd make a notation. This type of kniticking and point deduction is a deterrent to this hobby. JMHO

Brian------


I'd say it's pretty much a moot point. I'd be amazed if any judge would even check for the possibility of 64-69 "2 hole shims" being slotted on the inner end, let alone be able to discern this even if they attempted to check with a mirror or any other contrivance. I think they'd need x-ray vision. There's only one guy I know of that has that and I don't think he judges Corvettes.

[Richard G.]

Re: C2 trailing arm shims

Joe get my vote for some common sense on the shim issue and some humor to boot.

Because I like pictures below are picture of the original shims from my 1963.

[Edward D.]

Re: C2 trailing arm shims

I do a lot of C2 and C3 alignments. I'm probably the only shop in my region who will touch the rear alignment of these cars. For pre-1969 cars that originally used the longer 2 hole shims I always setup the alignment with the later slotted shims. If its a driver (won't be NCRS point judged) I leave those in and will even drill the holes in the frame for the 4" safety cotter pin. For owners that want original two holes I remove the slotted shims and install an identical thickness of shim pack inner/outer of the original type. Its really not that difficult to do. Easy removal of the trailing arm bolt is a balancing act, you have to have the vehicle weight on the arms and bottle jacks under the spring end and frame, plus a ratcheting strap around the arm and your lift ramp to get to a balance point where the bolt will slide out easily and allow you to insert the 2 hole shims and slide the bolt back in. You do not need to hammer in any shims, they should slip fit in tightly and when you tighten the castle nut on the bolt they will be firmly in. You should not be able to move the shims by hand after tightening if properly done. Same goes for the newer style slotted shims that are tucked into the frame pocket, they ought to be tight after torquing the nut/bolt. One other pointer, if using slotted shims install the long safety cotter pin before you torque the nut.

[Gary B.]

Re: C2 trailing arm shims

Edward,

Thanks for the descriptions of the process. Very informative and interesting.

Gary