Rotor runout Options

[Olympic 914]

As one of my winter projects.

I had a slight pulsing in the brake, really only feel it just when coming to a stop. no noticeable pulling to either side.


So I hooked up the dial indicator to check the rotor runout. rears were .004 and .005
right front was .004 left front was .016

For what its worth I am running 911SC struts with A calipers. the rotors are separate from the hub. i did carefully torque the new rotors down to 18ft lbs in a star pattern when installing them.


Thinking I have found my Smoking Gun in a warped rotor, I ordered 2 new front rotors and new pads, although the old pads only had 16K on them and still looked very good. Figured new rotors get new pads.

So I get the left side back together today and was working on the right side, when I got the idea to check the runout.

Well wouldn't you know it the left side with a NEW rotor had .016 runout. WTF??

Right side back at .004, same as before.

any one have this kind of problem before?

the only thing I can think of is, when I installed the bearing races back when I first put them on, one of them wasn't seated all the way. or somehow got in there slightly crooked.

guess I will take it back apart and try to drive the races in further.

we shall see what happens.

[Olympic 914]

Pulled the bearings out and tried to reseat the races, made no difference.

And it seems that the bearing preload remains constant when spinning the rotor.

Marked the high and low spots on the rotor and hub.

Pulled the rotor off and dressed the mating surface of Hub/Rotor with a file, in case there was a high spot. also re-clocked the rotor to see where the high spot moved to.

The high spot stayed with the mark on the hub. So I guess my old rotor was probably OK,... too late now I already sent it off to the scrap pile.

So now I have to figure out what is going on with the hub. The races look like they are seated ok. but I may have to investigate further.

I recently moved and I don't have my lathe set up yet,

If I can devise a way to hold it I may be able to indicate off the race edge to see if it really is in there crooked.

I can't imagine that the rotor mounting surface on the hub was machined wrong. IDK

a small difference at the bearing would translate to much larger at the rotors edge.