Rotors runout

[Olav]

Hi!

The runout on my C5 front brakes is about 0.004" or 0.12mm Will this cause problems og is is OK. Think the limit is 0.003 on the vette... Will this cause pumping pedal/ vibrations ?

Olav

[Olav]

Ttt

[Apogee]

Ideally, less axial runnout would be better, but what you have should at least work until you can properly address the issue. You probably will feel some of the runnout back at the pedal and it will probably get worse, not better, as things wear in. The floating calipers are certainly more forgiving than the fixed ones when dealing with issues such as this, but not completely forgiving. IIRC, you're running the stepped-bore, quick take-up S10 master cylinder on a hydro-boost no less, so a little pad knock-back for you may not even be noticeable. It's not even comparable to what guys running manual systems with small bore master cylinders have to contend with.

Is the source of the runnout your hubs, the rotor or a combination thereof? If it's a combination, I would suggest trying the rotor in it's 5 possible orientations relative to the hub and rechecking the runnouts. You could always have the rotors turned with an on-car lathe, but that's usually a last resort since it only addresses the symptom and not the real problem.

Tobin
KORE3

[Olav]

I put indicator on the hub and also the rotor. The problem is on both parts. When i started the runout was twice readings I have now. I tried the rotor all 5 places to get the best result.
The tapered washers/ shim are they waste of money?

Olav

[Apogee]

It sounds like you have access to machine tools, so is truing the hubs relative to their bearing bores an option or is that something you're trying to avoid? Just for reference, whenever I've indicated in our billet hubs during an installation, they tend to be within .0005" to .001" of true. Shims seem to work well initially, however it's a couple of additional contact surfaces to get dirt and corrosion between which seems to offset any initial benefit over time in my experience. Let us know what you end up doing since I'm sure there are others who have had similar issues and questions.

Tobin
KORE3

[Olav]

Then I probably have to indicate the hubs when they are on the spindles. Mark the readings. Put the hubs in the lathe and align to the same readings as on the spindels. Then Resurface!

Olav

[Apogee]

That would be one way of doing it. I would make sure that your bearings are good before doing anything though. If your flange is true to the bearing centers, you could chuck off that and indicate both bearing counterbores until you were happy, then face the flange. When you turned the flange, did you chuck off the snout of the hub or internally on a bearing counterbore?

Tobin
KORE3

[Olav]

That would be one way of doing it. I would make sure that your bearings are good before doing anything though. If your flange is true to the bearing centers, you could chuck off that and indicate both bearing counterbores until you were happy, then face the flange. When you turned the flange, did you chuck off the snout of the hub or internally on a bearing counterbore?

Tobin
KORE3

When i machined the hubs I put the snout in the chuck on the lathe. Indikated the bore for the inner bearing radial and and aksial on the end of the hub.
I did not machine the flange on the hub only the outside. The rotor has a light press fit to the hub. 45 deg. edge on the outside to clear the radius inside the rotor.

As long as I did not machined the flange on the hub the rotors / hubs must have uneven been before i started.
I could have done something wrong when i machined the parts. I'm not perfect . But both rotors!!!


Olav