What is "runout"
 

In several post ,I have noticed people talking anout mearsuring "runout" on the wheels and/or brake rotors. What is it measuring and how is it done?

Just wondering
Rick

Runout is the out of plane wobbling that a rotor would exhibit if it was warped, for instance. Runout also can occur on cylindrical shafts, but I think you're referring more to the rotor application.

It is usually measured with a dial indicator. The indicator is attached to a fixed surface and the pointer is allowed to rest on the rotor. As the rotor is rotated, the pointer will move indicating how far the rotor moves out of plane.

Mike

A rotating assembly should have minimum movement transversly to to it's normal plane of motion

i.e side to side movement

Usually measured w/ a dial indicator, but is often easily observable by the eye.

Run out on a tire can/does mean the same thing as out-of-round. I think Bill's definition is more correct technically, but I have used the term for ecentricity, be that right or wrong.

Tires can have side to side anomallies, but I would call that FUBAR (in this instance, R= reason :D )

Bill and IROC have it right...run out as commonly used is the deflection of a disk/rotor or wheel (items we expect to be perfectly flat in its radial plane) Eccentricity is the degree of offset bore centers, such as the bore center of a wheel half to the wheel center when speaking of a two or three piece wheel.

Runout is the grassy area that you find after performing an early apex at 5 mph faster than your traction allows :)

Ok then...runout is what happens when you buy a 911 and spent too much time on BBS' like this one....you eventually runout of money :D

grass? what track is that? Sounds nice...is there a viewing area with margaritas?

I'm guessing the tracks you have out west are in pretty dry places. Laguna Seca and some other tracks look like deserts. Here in the East we have nice grassy areas or lawns around the track and even right next to the track where there aren't gravel traps. People camp right at the track in some places.

Remember those water slide things when used when we were kids? That's what damp grass runoff feels like - like you are speeding up instead of slowing down.

-Chris

Does anybody know if the runout specs are the same for ALL rear M calipers -- no matter what year the car is?