I had this problem on some aluminium hubs on my sports racer. My thoughts
on a fix:
The bearings themselves are probably not the problem. They may be
incorrectly installed, or repeated bearings changes may have permanently
changed the seats and bores that they press into. I'd be very sure that
the bearing seats and bores are as perfect as they can be, and that the
install is correct.
Then, I'd be very sure that the disc mounting surface on the hub is what is
actually wobbling. I do this using a dial indicator on the hub installed
on the car. Swapping the hubs side to side on the car may tell you
something, as well.
I fixed mine by determining that the opposite face to the disc mounting
surface on my hub was true, which allowed me to chuck the hub in my lathe
and take a clean up cut on the disc mount surface. This will fix the
problem pretty much permanently, and new discs should be able to mount
straight on to the hub.
The other way is to have the disc skimmed on the car - you used to be able
to have this done a specialty brake shops, to correct exactly this problem.
keep in mind that you should also check the runout on the wheel mounting
surfaces - this will help you decide where the error is originating.
Brian
At 10:58 AM 05/29/2000 -0400, AnalogMike@aol.com wrote:
>Hi,
>
>I rebuilt my front hubs with new bearings and races, and installed new
>brake rotors on my '73 911.
>The brake disks now show about the max factory runout (.008) which is a LOT.
>I thought it might be the disk, so rotated it and remounted to the hub
>and found the hub is actually the problem as the same part of the hub
>was still wobbling the same. I did one hub rebuild myself and one
>at a machine shop and both are off similarly.
>
>Braking at Watkins Glen afterward was not good, high braking pressure
>caused shuddering. My last set of brake disks shuddered for several
>events then stopped, maybe the old disks wore off the .008 from the
>high points?
>
>I am not sure where the hub wobble comes from, I don't quite
>understand how the bearings/races/spindle/etc work together.
>I guess the wobble is due to the bearing
>races not being perfectly squared, or the hub not true??
>Could it be the spindle which I messed up a but when installing the
>spacer ring?
>
>Anyway, how do I fix the problem:
>
>1) Have the hub machined flat where the disk mounts?
>This would seem to get the brake disk nice but the wheel may
>still shimmy a bit as the wheel mounts to the other side of the hub.
>
>2) Try to straighten the bearing races somehow, maybe bang
>on the race at the "high" point of the hub?
>
>3) Am I missing something? Is this a common problem??
>
>THANKS!!! (Pocono race next week).
>
> Regards, mike piera AnalogMike@aol.com '72 911S '73 911RS Clone
>
> my racing pages - http://www.analogman.com/911
>
> ~^v^~ aNaLoG.MaN ~^v^~ vintage guitar effects www.analogman.com
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