Rear wheel bearings for C2s?

[Joe L.]

Re: Rear wheel bearings for C2s?

Duke;
Failure to follow these instructions by leaving the front wheel bearings preloaded and not backing off the spindle nut to the specified clearance range usually results in rapid failure.
No I can't explain it.
May have something to do with the sliding fits on the spindles verses an interference fit. Or heat building from over greasing. The "bearings last longer preloaded" is the result of specific testing done by the bearings manufactures and may not be true in every instance. May have been related to oil bath only but I would have to dig out the books again to be sure. In general terms it is very true. Add dirt, incorrect lubrication, incorrect set up and all bets are off. The studies were controlled studies that attempted to eliminate these variables. Best to stay within factory recommendations. Possibly my bearing engineering comment was ill placed for this discussion?

Interesting GM's clearance settings allowed up to .008 axial play. The available factory shims allowed one to meet this specification as they come in .006 increments. This allows one to hit the factory specified clearances but reducing it to .001 or .002 sometimes difficult. I use a surface grinder to reduce one of the thicker shims to the required thickness. Most don't have this luxury. I find differences in the center spacer's width. Swapping them side to side or having an extra around usually helps get this spec a little closer to the .002 which I prefer. This is especially important with a disc brake car.

Richard------


GM specifically cautions that no attempt should be made to adjust the thickness of the shims.

[Richard G.]

Re: Rear wheel bearings for C2s?

"GM specifically cautions that no attempt should be made to adjust the thickness of the shims."

I understand you are just passing on GM information and not judgment.
What could the possible logic be behind the caution?
I would bet the ones I grind are flatter and more accurate than the stamping they made them from?
What are they cautioning against, putting them on a steel plate and massing them thinner with a BFH?

Difficult to understand the caution is all I am saying.
Rick

[Gary R.]

Re: Rear wheel bearings for C2s?

The bell spacer in every arm I take apart is out of parallel up to 005", I parallel grind them. The shims come in sizes too wide to dial in the spec's I am looking for so I final grind shims within a few tenths to get them where I want. All the parts go together flat and tight and the dial in doesn't change from setup tool to final install.

Now with that said, seeing how some rebuilders set up rear bearings - professional or DYI- I can understand GM's statement. However, correctly done there is no issue, same for fitting a solid pinion sleeve in place of the stock crush sleeve.

[Gene M.]

Re: Rear wheel bearings for C2s?

If you don’t have the resources of Gary to custom grind, there are tooling shims available in correct diameters (within a few thousands bigger) in increments of .001 or less. They are hardened and should get you the stack up to zero clearance the taper roller bearings. I don’t recall the web site but some investigation should get you there. They were perfect for my cars in obtaining zero clearance.

Those tooling shims in combination with the available shims from Corvette jobbers should get you a perfect fit. Be wise and check all the Corvette jobber pieces for precise dimensions and squareness/parallel as Gary advises.

[Joe L.]

Re: Rear wheel bearings for C2s?

"GM specifically cautions that no attempt should be made to adjust the thickness of the shims."

I understand you are just passing on GM information and not judgment.
What could the possible logic be behind the caution?
I would bet the ones I grind are flatter and more accurate than the stamping they made them from?
What are they cautioning against, putting them on a steel plate and massing them thinner with a BFH?

Difficult to understand the caution is all I am saying.
Rick

Rick------


My thought has always been that the shims are case hardened, not through hardened. So, by adjusting them the case hardening is lost, at least on one side.

One other thing: a lesson that I learned a long time ago is that when GM specifically cautions about something, there is usually a good reason for it. They most often don't state what the reason is but if one does not observe it, one may suffer the consequences.

[Gene M.]

Re: Rear wheel bearings for C2s?

Rick------


My thought has always been that the shims are case hardened, not through hardened. So, by adjusting them the case hardening is lost, at least on one side.

One other thing: a lesson that I learned a long time ago is that when GM specifically cautions about something, there is usually a good reason for it. They most often don't state what the reason is but if one does not observe it, one may suffer the consequences.

But realistically when the bearings are shimmed correctly and tightened down torqued as they should be there is no relative motion of the shims and sleeve relative to anything that would wear. Everything creating the bearing fit is torqued up solid and cotter pinned. Certainly a shim or sleeve out of square/parallel is worse than the surface ground true a bit into case hardening.