GTR1999

I ave some time off this year so I'm getting ready to get back to various parts of the 72 I took off a year or so ago. Tonight I had my buddy true the rear spindle/rotor for me in his 12" lathe. I hoped to do this in the 10k South Bend I have by the rotor diameter is just too big. For those that want/have access to a 12" or larger lathe and are doing thier own rear beairngs this is what I did.
I first marked the relationship between the rotor/spindle, removed everything, cleaned the spindle, rotor, filed down any high spots in the mating areas of them, tapped the spindle rivet holes 3/8-24, used a 82* countersink on the rotor rivet counterbore, and finally bolted them together using 3/8-24x5/8 flat socket screws.
I had to remove the lug studs to mount it in the lathe. We held the outer end by the spindle OD and used a live center in the other end. Put an indicator against the rotor and measured runout. .004" on th eoutside/ .003" on the inside surface. This are the originals, never turned with 55k miles on them. they "miked" at 1.251" to start. Turned the outside surface by holdingthe spindle on the large bearing journal.
Finished with .0005-.001" runout and 1.244" thickness. I'm going to paint the hubs with POR15 then separate the spindles to start rebuilding them with new bearings, it will be interesting to see how much the runout changes when I bolt them back together with the bearings?
Did anyone ever assemble them with the rotor attached? I thinking the load pulling the bearing throught the housing my make it hard to do?

Any input?
Thanks,
Gary

Barry's70LT1

I see no one has commented on your post.
I am a firm believer in having the runout perfect. So many problems are
eliminated by having true rotors.

I have a question.....
If I were doing this procedure, I would have turned the spindle separately
from the rotor, and then as well, turned the rotor separately.
Then, would not the end result be the same.??

The only difference in procedures is that if a rotor replacement is required in
the future, then a true rotor could be added without any runout issues.

Thanks
Barry

GTR1999

Hi Barry,
I didn't want to turn the spindle at all because it would then be undersize. I have the spindle setup tool for the bearings and it is .001-.0015" undersize and the bearing slide right on, but I don't want a slip fit on the spindle. I have seen and had done,many years ago,the rear rotors turned separately and they looked great except they weren't concentric with the spindle center line. Sometimes the runout was greater then it originally was! That's why the factory turned them together.
I would like to know how much oversize the rough casting was and what machine they turned them on. I had to remove the studs in order to get the outer spindle "chucked" the 12" Hendley Lathe we used. I would think any local machine shop wopuld have a lathe larger then the 12" so it would be easier to setup on.
Gary

Barry's70LT1

Hi Gary..
This fall I rebuilt my trailing arms, bushings/bearings, the whole thing.
When I removed my spindles, both were twisted, however my rotors
were in excellent condition.
For convience and cost, I purchased two used spindles from the local
Corvette graveyard here.

When this guy sells used spindles, he always removes the rotors and
studs and sends them to a machine shop to have the flange face machined
true to the spindle.
This worked fine for me, as one of my original rotors was actually true, and
resulted in less than .001 runout.
The other one was about .008 out. I shimed it to .0015, rather than have
my original rotor turned.

Just though I would share that little bit of trivia.

Barry

GTR1999

Barry,
Sorry I misunderstood your previous post,I thought you were referring to the spindle shaft where the bearing race rides. I did check the spindle flange face and had .001-.0015 runout before doing any other checks. After I bolted them up I had .003 on one side and .004 on the other face of the rotors. That's when I faced them and they are now true-at least until I unbolt them again. :smash:

GTR1999

Barry,
I forgot to ask, where were they twisted, at the splines?
Gary

Barry's70LT1

Gary...
Yes, they were twisted at the spline. About a 1/4 of a spline. The left side
was worse than the right.
They took a lot of hard runs over the past 31 years.

Barry

Ingar, Norway

I aligned both my spindle flanges in a lathe. Solved the severe air sucking problem I had. The rotors were ok.
Also went for slip fit. Don't want to go through that PITA job of dismantling the spindle once more. This also make checking/greasing a breeze.
Have 6k miles this season and no problems.

Tom454

All you folks who are installing o-ring caliper (pistons) to fix your "spongy brake pedal".... listen to these guys... they know how to do the job the right way. Address the rotor runout first- then deal with the calipers. This is the stuff that separates the men from the boys. Awesome!