C3 trailing arms question

[Ken B.]

Was looking for some opinions...My trailing arms are original and have never been rebuilt to my knowledge and by the looks of them.Is it better to rebuild them or do a swap with ones that are already rebuilt by...lets say Ikerds. Thanks in advance
Ken

[Jeff D.]

Re: C3 trailing arms question

I send mine in for rebuild when I have them done. They have a casting date on them and if they are original you will want to keep the correct dated parts. Ikerds does a great job.

[Gerard F.]

Re: C3 trailing arms question

Ken,

If you want to get your car back on the road in a hurry, buy new or rebuilt trailing arms complete with the riveted on rotor. The changeout is a day, and I got a one week delivery from Ikerd's (through Paragon) on my 67, after a wheel bearing burn out. It ain't cheap though.

If you have the time, and are able to have your car up on blocks for an extended time, then you can take your old ones off, send them in to be refurbed, and then wait for them to come back. I think Ikerds, as well as Bairs and other outfits will do this. If you are going to do one, you might as well do both.

[Steven B.]

Re: C3 trailing arms question

I like to keep my original parts whenever possible. 'You only have original parts once. Bair's is excellent.

[Jim T.]

Re: C3 trailing arms question

I am still enjoying my rear spindles that www.bairs.com riveted my rear brake discs to about 20 years ago.
Chev garage did warranty replacement rear wheel bearing work and separated the spindle and brake disc. Result was runout and brake calipers pumping air, loss of rear brakes.
Only wish I had known of Bair's services earlier, would of saved money having it done right.

[Gary R.]

Re: C3 trailing arms question

Keep your originals if they are not bent or rotted, there are plenty of guys who exchanged and ended up with arms not as good as the originals.

Aside from that you should be asking who ever does the work what bearings they use, should be Timken-USA, not imported. What spec the bearings will be set to and if the runout will be correcte if the rotors are installed. Ask what grease is used.

Any qualified shop will answer these questions without a second thought. Be wary if you don't get exact answers. I've rebuilt many of these and repaired a lot of others work. Some of the things I've had to correct:
imported bearings, wrong endplay, runout over 005", bad repairs to the PB, bushings not compressed and flared, damaged spindles, bent arms.

Good luck. If you look up my thread on this job it may help you check them at home before you commit to anyone.

Also this response is not in regard to any business listed in this post. I deal with both Bairs and Ikerds,no problem. A lot of the bad work I fixed came from owners, local garages, dealerships, even some corvette shops.

[Phil D.]

Re: C3 trailing arms question

I've rebuilt many of these and repaired a lot of others work. Some of the things I've had to correct:
imported bearings, wrong endplay, runout over 005", bad repairs to the PB, bushings not compressed and flared, damaged spindles, bent arms.

How do you measure runout exactly? I didn't see a procedure in my book. I just had my trailing arms done by a local corvette shop which was highly recommended by a fellow ncrs member. Installed them and took a test drive around the block and hear a noise in sync with the wheel rotation at the right rear. Put it up on the lift and ran it in gear to see whats going on and wheel was visibly wobbling. I put a dial against the face of the hub at the very edge outside the bolt circle and measured just a hair over .005". I'm guessing I measured it right and I need to remove the arm and take it back for them to correct it. What can be done to get it down toward zero?

Guess I won't be making the LSCC meet this weekend.

Phil

[Terry M.]

Re: C3 trailing arms question

Did they rivet the rotor tot he hub? If not (and most rebuilders don't) mark the rotor so you can get it back to the original position and try rotating the rotor one wheel stud hole, and remeasure. This process is called "indexing" and you can do it repeatedly (well at most five times) and see if you can reduce the run-out. Maybe you can make the meet yet, if you get lucky.

[Gerard F.]

Re: C3 trailing arms question

Terry,

Doesn't the hub go on the spindle only one way. So that the hole in the hub lines up with the parking brake adjustment wheel. Or am I missing something here, being just a C2 guy.

Thought I saw something about shims on the lugs in a distant thread in the past.

[Terry M.]

Re: C3 trailing arms question

Gerry, You are right about the parking brake adjustment hole locating the rotor in one orientation. My aim, and I should have stated it, was to give Phil a shot at going to the meet WITH functioning brakes. Also, given the choice between functioning brakes and access to the parking brake adjustment -- I know which I would chose, but that is just me.

Yes there is a shim kit available to resolve the rear brake rotor issue more professionally, and there is the rivet and cut the rotors service (which is how the factory did it) offered by some trailing arm rebuilders. Either of these are good long-term options, but both take more time investment than Phil seems to have at the moment. He ought to put them on his list for the long-term however.

[Gerard F.]

Re: C3 trailing arms question

Just wondering, if Phil had both sides done at a shop, and the rotors are unriveted, and there is excessive runout on both sides, maybe the shop swapped the rotors on each side.

Maybe check the other side, a swap back might be an easy fix.

[Joe L.]

Re: C3 trailing arms question

Terry,

Doesn't the hub go on the spindle only one way. So that the hole in the hub lines up with the parking brake adjustment wheel. Or am I missing something here, being just a C2 guy.

Thought I saw something about shims on the lugs in a distant thread in the past.

Jerry-----


Yes, if the rear rotor is re-indexed to the spindle, the parking brake adjustment holes in the rotor and spindle will no longer line up. However, that presents VERY little problem. All one needs is a good 1/2" drill and a sharp drill bit. Using the parking brake adjustment hole in the rotor, drill a new adjustment hole through the spindle flange. No problems created and no one will ever know the difference.

[Gary R.]

Re: C3 trailing arms question

You need to see exactly what you have by using a dial indicator. You have to be sure there in no movement in the base as well as this can lead to false readings. Feel and touch go a long way in getting a correct reading. I don't trust those cheap import indicators and bases either. I c clamp the base so I know there in no movement and use an Starrett indicator.

I set them up with the arm off the car when I rebuild the arms.

I was never a fan of the index method either, you loose the adjustment on the PB shoes and it's just a hack way of doing it.

The best way is to rivet or bolt them on and have them faced. This is not as practical for most shops to do and make assembly a hassle. An on the car lathe would work but finding a shop with one could be a problem.

I like to have access to the PB, so I never rivet them back on. I tap the spindle and bolt them on. In the process I shim using 001 increment SS shim stock to dial in runout under 003". "set it and forget it"!

I have faced spindle flanges,used NOS,original,import and SHP rotors and they all runout. I found it is usually better not to face the flanges as long as they still have the original turn marks. The rotors will runout in most cases. Some new spindles and rotors are near perfect others are not.

005" total will probably be ok but I like under 003"

[Joe L.]

Re: C3 trailing arms question

Gerry, You are right about the parking brake adjustment hole locating the rotor in one orientation. My aim, and I should have stated it, was to give Phil a shot at going to the meet WITH functioning brakes. Also, given the choice between functioning brakes and access to the parking brake adjustment -- I know which I would chose, but that is just me.

Yes there is a shim kit available to resolve the rear brake rotor issue more professionally, and there is the rivet and cut the rotors service (which is how the factory did it) offered by some trailing arm rebuilders. Either of these are good long-term options, but both take more time investment than Phil seems to have at the moment. He ought to put them on his list for the long-term however.

Terry-----


The factory had the advantage of machining the rear rotors as an assembly with the spindles using UNFINISHED rotors. That provided plenty of "meat" to machine the rotors to NEW thickness AND obtain runout within spec.

Many GM spindles are WAY out on TIR on the spindle flange. So, if anything but the originally installed rotor in the originally installed position is mated to the spindle, the TIR will be so excessive that the rotor will have to be cut below minimum thickness to get the assembly into TIR spec.

In many cases, the only way to do this and maintain proper rotor thickness is to first machine the spindle flange to achieve minimum TIR, then machine the rotor so that there is minimum runout measured from the spindle flange mating surface to the brake pad surface, and, finally, rivet or bolt the assembly together, measure TIR and correct if necessary with a small finish cut to the rotor. This effort results in a LOT of machining and COST. There are at least 2 ways around it, though:

1) correct most of the excessive TIR with the tapered shims. Then, finish machine the spindle/rotor assembly, IF NECESSARY, to achieve in-spec TIR;

2) use a new aftermarket spindle as available from International Axle which has a guaranteed TIR on the spindle flange of 0.0005" or less in conjunction with new SERVICE rotors which are usually machined to less than 0.001" TIR measured from the spindle seating surface to the barke pad surface. Rivet or bolt these parts together and you'll almost always be WELL WITHIN the specified TIR with no machining required, at all.

[Phil D.]

Re: C3 trailing arms question

Well I've been messing with it since I got home from work. I tried swapping the rotors from side to side thinking that mabe somehow I or the shop got them switched, but that only made it worse, so I guess they're on the sides they came off of. I'd always thought of indexing the same as Gary, but I tried it as suggested and it was very interesting, however, not a solution. I could get the runout on the rotor face down to .006" by moving it one hole counterclockwise, however, that increased the runout on the hub face (rotor hat) from .008" to .012". The best I could get on the rotor hat was .008" at the default position. Indexing only made that worse. I wish I knew if the rotors were original to the car. They were not riveted when I bought the car, but they've got a bunch of holes and they all line up if that means anything.

So question. Is there something that the corvette shop did or could have done wrong in the rebuild process that got the runout out of whack or is this just inherent in the original poor build quality that's just now showing its ugly face?