How to set front wheel bearings

[norvalwilhelm]

I have been asked a number of times how to adjust the front wheel bearings. This is NOT my method but one that I like and I follow it. I have tested the results and agree with it.
This is from the Article BigBlock from Hell. I am copying it.

Our lip seals on our brakes have a .010 limit in flex before they start pumping air. This is bearing play plus rotor runout added together. If you accept .008 bearing play it leaves nothing for rotor runout.

The allowable front wheel bearing clearance is .001-.010 with .003-.005 prefereable. Follow that and you will have problems.

In 63 the service manual had us torque the bearing nut to 12 ft/lbs and back off one nut flat and install the cotter pin. This gave us 0-.007. in 71 manual the clearance was increased to .001-.008.

Later chevy said to tighten the nut to 12 ft / lbs then back off until just loose then hand tighten until one of the cotter pin holes lines up. This is .001 to .005

This is the method recommend. Global West whoever they are came up with this and I like it.
While spinning the wheel in the direction of forward vehicle travel, torque the bearing nut to 15ft/lbs, this sets the bearing and grease.
Back off the nut until loose then while rotating in the direction of travel retighten to 50-60 inch pounds, Install the cotter pin without backing off to the nearest cotter pin hole. This give .0005-.001
Now the problem is there is no cotter pin hole??? Check and you will find there are TWO 2 holes in the spindle and the chances are good one of them lines up. If not then you can use valve spring shims under the nut, install one shim try the proceedure agian and check the TWO cotter pin holes.
I have used this for years along with trued/shimmed rotors and the most runout I have in one wheel is .003 total for bearing and runout.

 

[JohnZ]

The spindle nut has 20 threads per inch, for .050" per revolution. The nut has six pin slots, which gives .008" per slot. Having two cotter pin holes cuts that in half, for the possibility of fine-tuning it within .004" without shims. As you said, .004" isn't close enough, so you have to shim to work within the .000"-.004" window to get as close to .0005"-.001" as possible.

 

[norvalwilhelm]

The spindle nut has 20 threads per inch, for .050" per revolution. The nut has six pin slots, which gives .008" per slot. Having two cotter pin holes cuts that in half, for the possibility of fine-tuning it within .004" without shims. As you said, .004" isn't close enough, so you have to shim to work within the .000"-.004" window to get as close to .0005"-.001" as possible.

That is the method I will now use. Since I posted SCWDuke from Corvette C1/C2 told me of that method also and I like it better.

 

[mrvette]

Why not just go to O ring calipers and forget about all that???


GENE

 

[tomtom72]

Hi Guys, I have a few sincere questions since I am not a mechanic. Am I correct in thinking that "O-ring" calipers do away with the original chevy rubber caliper piston seal, the seal that looks like a circular door sweep, and replaces it with an O-ring to seal the caliper piston bore? Also I have a stupid question about front brakes on a C3. If you bought new rotors or if the old rotors were still thick enough to be re-used and you had then cut to "true" them up, wouldn't the "trued" rotor have no waves in it? Or is it impossible to "true up" a rotor no matter how good the lathe is? I guess I always thought that a "trued up" rotor had zero run out, I'm wrong or I obviously don't know enough about what's really going on at the front spindles. Any help would be great, thank you. Tom

 

[Vettehead Mikey]

Why not just go to O ring calipers and forget about all that???


GENE

Ummm, cause not everybody's middle name is Bubba??

O ring calipers are very good and can be seen as a valid alternative to the stock configuration, but I don't understand why people don't go after the root cause of a problem and prefer to put band-aid fixes instead.

But that's just me.

 

[Vettehead Mikey]

Hi Guys, I have a few sincere questions since I am not a mechanic. Am I correct in thinking that "O-ring" calipers do away with the original chevy rubber caliper piston seal, the seal that looks like a circular door sweep, and replaces it with an O-ring to seal the caliper piston bore? Also I have a stupid question about front brakes on a C3. If you bought new rotors or if the old rotors were still thick enough to be re-used and you had then cut to "true" them up, wouldn't the "trued" rotor have no waves in it? Or is it impossible to "true up" a rotor no matter how good the lathe is? I guess I always thought that a "trued up" rotor had zero run out, I'm wrong or I obviously don't know enough about what's really going on at the front spindles. Any help would be great, thank you. Tom

The o-rings do indeed replace the original V type seal.

A properly machined rotor should have no surface defects beyond the tolerance called up by the OEM and subject to the capability of the machine that the work is performed on.

Does that mean a rotor will have NO waves or runout? It will if you are measuring stuff to the ten thou of an inch (.0001"). The spec for waves (parallellism) is probably .001" and runout most likely the same or close. Others can confirm.

Any half decent shop can easily manage this spec.

 

[JohnZ]

The problem is that the original hub (or spindle) flange mating surface wasn't machined to the same finished tolerance as the assembly, nor was the rotor; that's why they riveted the rotors to the hubs and spindles and did the finish-machining of the rotor's friction surfaces to the final tolerance with the two parts joined solidly together. Machining the hub (or spindle) flange mating surfaces and the rotor mounting surfaces relative to the friction surface separately, accurately enough so that the finished assembly would always be within the required runout tolerance, would have been prohibitively expensive. That's why they were riveted together prior to finish-machining of the rotor's friction surface.

Corvette rotors will just about last forever when used with OEM organic pads; if they are truly scored (but can still be be turned and remain above minimum thickness spec), they should be turned ON THE CAR - most professional brake shops have the equipment to do this.

Most average brake shops have no clue about the requirements of '65-'82 Corvette fixed-caliper brakes, as they stopped making them over 20 years ago; everything they work on today has single-piston floating calipers, which don't require the tight lateral runout tolerances that fixed-caliper systems do (unless they're working on Ferraris, Porsches, or Vipers, all of which use Brembo 4- or 6-piston fixed calipers).

 

[norvalwilhelm]

Why not just go to O ring calipers and forget about all that???


GENE

Hi Gene. I have 4 perfectly good stainless calipers that don't leak. Why go to the trouble and expense of replacing all the pistons just because the rotors are out and the bearings are not adjusted properly. With a dial inticator and a few shims I can bring the rotors into running true within .001 or .002. With the wheel bearings set to about .001 this puts my maximum runnout to .003 and well within the specs for a stock lip seals. I also feel if everything is running true it will also be smoother and last longer. I guess that is why my car can run at 100 mph plus with the wimper. I am a stickler for detail and O rings seals are just bandaids like already posted. Fix the problem.

 

[tomtom72]

Thankyou Vettehead Mickey and JohnZ and Norval for the education! If you do any work on the front brakes & or wheel bearings you must bring the run out of the bearings + rotors to the specs listed here, right? If you do any work to the rear brakes & or rear spindles or spindle bearings & or parkingbrake you must bring the rotor+spindle bearings back to the correct "run out" spec? I now understand where I went wrong when I rebuilt my front brakes and rear brakes and parking brakes,I think. I had a recurring air problem because I did not perform the steps to verify the "run out" at both ends of the car. At the time, 1978, I was only familiar with sliding caliper disc brakes. I did not realize if the piston seal is on the piston runout becomes a governing factor to system integerty. I was lucky, I guess, that when I decided to do the rear spindle bearings via the local chevy dealer they found the stupid mistakes I made and told me about them and fixed it all. Thank you guys for turning on the lights for me. Tom