C2 Rotor runout question - Spindles ?

[Mark P.]

I cleaned my hubs, removed the lug bolts and draw filed over the holes to make sure there were no burrs. I then installed new Raybestos rotors with 3/8"-24 flat head screws instead of rivets. I then installed the lug nuts, new bearing races and had a machine shop turn the rotors with the races and centering bucks. They said the hubs were off a bit and had to take off about .015 of material off the rotors to get them cleaned up. I now thought I would have zero runout.

I installed them on my spindles with SKF BR2 and SKF BR6VP bearings made in Brazil and my runout is .006 on one side and .005 on the other.

Planning to ship them. Any tips on how to do that ?

Could my spindles be off a bit ?

My calipers are the later O-ring design style I believe.

Was .008 the factory limit ?

Thanks,

Mark

[Joe L.]

Re: C2 Rotor runout question - Spindles ?

I cleaned my hubs, removed the lug bolts and draw filed over the holes to make sure there were no burrs. I then installed new Raybestos rotors with 3/8"-24 flat head screws instead of rivets. I then installed the lug nuts, new bearing races and had a machine shop turn the rotors with the races and centering bucks. They said the hubs were off a bit and had to take off about .015 of material off the rotors to get them cleaned up. I now thought I would have zero runout.

I installed them on my spindles with SKF BR2 and SKF BR6VP bearings made in Brazil and my runout is .006 on one side and .005 on the other.

Planning to ship them. Any tips on how to do that ?

Could my spindles be off a bit ?

My calipers are the later O-ring design style I believe.

Was .008 the factory limit ?

Thanks,

Mark

Mark------


I'm surprised that the TIR measured on the rotors mounted to the spindles is as good as it is. The rotor mounting surface on GM spindles is often WAY OUT on TIR. That's because I don't think that GM held a very tight tolerance on these because they were going to machine the unfinished rotor with it riveted to the spindle as an assembly. So, the finished assembly would be within TIR specs even if the spindle was not.

I think your runout will be OK when used with o-ring calipers.

[Richard G.]

Re: C2 Rotor runout question - Spindles ?

Might try this?
Pull the rotor and rotate one bolt hole and torque the nuts and check the run-out.
Do this for each bolt position and see if there is a sweet spot. Mark the stud and rotor with paint after assembled at the low tolerance point.
This should note the position for future reference.
Did you also measure at the hub for run-out before the installation?
Easy to stack tolerances and get further off than one might think.
Remember to measure at the same distance from the center each time.
Rick

[Mark P.]

Re: C2 Rotor runout question - Spindles ?

Joe - the hubs had a machined surface but it wasn’t a very fine cut, The factory GM rotors must have been thicker than 1.25" which is what my new rotors measured. I just checked my rotors again for thickness and about .020 material was removed. Between the bucks and bearings, something might have been a bit off.

Richard - I will try indexing them before I resort to shimming. The lessons learned would be not to get new rotors turned on the hubs but instead index or shim to an acceptable runout. Losing .020 of my rotor thickness was a big price to pay.

Thanks,

Mark

[Michael W.]

Re: C2 Rotor runout question - Spindles ?

My calipers are the later O-ring design style I believe.

gm never used o-ring calipers.

[Joe L.]

Re: C2 Rotor runout question - Spindles ?

Joe - the hubs had a machined surface but it wasn’t a very fine cut, The factory GM rotors must have been thicker than 1.25" which is what my new rotors measured. I just checked my rotors again for thickness and about .020 material was removed. Between the bucks and bearings, something might have been a bit off.

Richard - I will try indexing them before I resort to shimming. The lessons learned would be not to get new rotors turned on the hubs but instead index or shim to an acceptable runout. Losing .020 of my rotor thickness was a big price to pay.

Thanks,

Mark

Mark------


GM started with UNFINISHED rotors riveted to the spindle, front or rear. Then, the rotors were machined to finished thickness of 1.250" on the spindle center. This cannot be done in SERVICE as there is no way to obtain unfinished rotors.

If indexing does not get you where you want to be, Raybestos has available tapered shims to correct runout. You would have been better served by using these shims prior to doing any machine work on the rotors. I do not recommend machining the rotors to correct runout for exactly the reason you mention----loss of rotor thickness.

[Gary R.]

Re: C2 Rotor runout question - Spindles ?

Mark
If you like I can call you and go over the procedure.