Brake rotor with .003 runout - will that cause shudder?

[JMI]

So I posted earlier (http://www.bimmer.info/forum/showthread.php?t=33872) about turning rotors. Got out a dial indicator to check amount of runout. The front passenger side was spot on with no runout but the driver side has .003 of an inch runout. Is this enough to cause a fairly severe shake when braking moderately hard?

Thanks

[winfred]

that small amount shouldn't be a problem

[632 Regal]

was the rotor bolted to the hub?

[JMI]

was the rotor bolted to the hub?

Yes.

[Bill R.]

Did you check the runout with only the screw holding the rotor to the hub or did you have all the wheel bolts installed and torqued? If only the screw then the rotor can be cocked a little causing the slight runout you measure.... And any rust or debris that gets behind the rotor can cause it to cock slightly ..

At any rate as Winfred said, .003 shouldn't be enough to cause a shudder..





Yes.

[Jehu]

Have you checked anything other than rotors? Upper control arm bushings? Tire wear? Put a set of tires you know to be worn evenly ,maybe switch fronts with rears and see if that does it. It did on mine . I had already recently replaced the upper CA bushings and had just put on 4 new rotors (Brembos in front ,Zimmerman on rear with new Akebono ProAct pads all around $400.00 for everything btw) and went up on the highway to try bedding.As soon as i got up to around 50mph the front end started doing the hula dance . I swapped the front tires with the rears which were just weeks old at the time and that shudder was gonzo. Also do you have an aftermarket wheel on? If yes How about hubcentric rings? Those also stopped a shudder which was for all intents and purposes inndistingushable from the bad CA bushing and missworn tire surface shudder. The brake rotors only ever caused the slightest vibration and that when braking.

[JMI]

Did you check the runout with only the screw holding the rotor to the hub or did you have all the wheel bolts installed and torqued? If only the screw then the rotor can be cocked a little causing the slight runout you measure.... And any rust or debris that gets behind the rotor can cause it to cock slightly ..

At any rate as Winfred said, .003 shouldn't be enough to cause a shudder..

Busted! Yes it was with only the screw and not the lug nuts.

[JMI]

I had (and have) the shudder/shimmy which caused me to replace lower control arms and upper control (thrust) arms. Both sets are Lemforder with thrust arm bushings being of the M5 persuasion.
Wheels are stock basket weaves. Front rotors (Brembo) have less then 4000 miles.
I'm going to have the wheels/tires rebalanced. Maybe rotated as you suggest.
I have always been careful about the tightening sequence of the lug nuts and their torque value.

Thanks

[bsell]

I had (and have) the shudder/shimmy which caused me to replace lower control arms and upper control (thrust) arms. Both sets are Lemforder with thrust arm bushings being of the M5 persuasion.
Wheels are stock basket weaves. Front rotors (Brembo) have less then 4000 miles.
I'm going to have the wheels/tires rebalanced. Maybe rotated as you suggest.
I have always been careful about the tightening sequence of the lug nuts and their torque value.

Thanks


You said runout...you mean like a warped record (LP)? Did you measure the change in thickness all around both rotors? I forget what that is called but if there is enough variation in the thickness of the rotor, you can get vibration problems just like the warped LP (runout) problem.

Brian

[Barney Paull-Edwards]

check them off the car, then check the hub run-out.Sounds more like other problem to me.Correct wheels?

[GoldenOne]

Hmmm...could someone go into detail what run-out is and how one can check for it? I think is could be what is causing my braking shudder...