Wilwood rotor runout

[Rsnake]

I have a little over 300 miles on the roadster and have had a brake pedal pulsation above 60 mph when braking. So last night I pulled all the wheels to check rotor runout. Of course all of them where around .001 to .0015 until I checked the rear passenger. The inner face was less than .001 but the out face was .006 and I am sure this is the source of the vibration. Has anyone else had issues with the wilwood rotors and will they send a new one?

[GFX2043mtu]

For best results rotors should be true to with in .0025”. If it’s over this then something is not right. Check to make sure there isn’t any thing between the hub and rotor. Chips of stuff can cause issues.

[NAZ]

Here's what Wilwood says about rotor runout: Rotor runout should be adjusted as soon as you receive your Wilwood components. Wilwood rotors are precision machined to ensure the rotor surfaces are flat and parallel. Sometimes hubs, bearings or other components have runout that cause the rotor to runout. As a rule of thumb, allowable runout should be .005” - .008”. Adjust the runout by re-indexing the rotor or by placing shims between the rotor and hub, or hat. Runout should be rechecked regularly. You can assume the runout to be acceptable as long as you are not experiencing brake drag, pedal oscillation or excessive piston knock back.

From my experience, .008" runout is going to produce enough pulsing you'll feel it. I agree with GFX above that you should check for debris on the mating surfaces before assuming the measured runout is from the caliper. If I recall an average human hair is ~ .003" thick so that will give you some frame of reference for these dimensions we're throwing around. Lets say you have a piece of dirt sandwiched between the hub and the rotor and that dirt measures .002" thick. The runout effect is going to be significantly more than .002" as where you measure runout is much farther from the center of the hub than the dirt and that is mechanical leverage at work.

[Rsnake]

I did check and the mounting surface on the hub looks good. The big issue is the back of the rotor is perfect, the outer face of the rotor is the issue so if it was debris on the mating surface both sides would have runout. I could have a few thou taken off but since it's brand new I feel it's wilwood's issue and they should replace it. Wilwood's recommendation of 5-8 thou seems a little excessive as you will feel that in the pedal.

[GFX2043mtu]

Wilwoods general recomendations are based on the rotor being true. If you have zero run on one side and .006” on the opposite then you’ll have one set of pistons not moving and the other pushing and pulling. With this displacement you’ll feel it. If the rotor thickness is true and the rotor flops around I still don’t like over .0025” but you may not feel it. With more run out things like threashold breaking become an issue and wheel lock occurs before it should and maximum braking becomes compromised. If it’s bad enough all breaking becomes compromised and you’ll feel the pedal, brakes, or both pulsing. When racing karts especially my 250 F/E we set all the rotors as close to zero as we could get. I found that if they where not less then .0025” I could tell as that wheel/s would consistently lock before the others when pushing it hard. Call wilwood and tell them about what you found when measuring the rotor and tell them about the pedal pulsation and they’ll help you out.