Subject: [Shop-talk] wobble in brakes

From: "John Niolon" <[email-masked]>
Date: Fri, 26 Dec 2014 13:12:06 -0600

2008 Suburban.... noticed lately that when I apply brakes I feel a vibration
or pulse like one of the rotors might be warped.  Rotated tires this week and
used a dial indicator to check for run out.  The right side was less than .001
the left side varied from .001 to .005.   Can 5 thousands show up in the pedal
??  can a shop turn that much out ??   the rotors have never been trued at
all...

thanks
John

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From: "Karl Vacek" <[email-masked]>
Date: Fri, 26 Dec 2014 20:40:49 -0600

Another possibility is pad material building up unevenly on rotors.  A set
of EBC Green Stuff pads on a Mustang years ago drove me crazy.  They'd pulse
and wobble, then later be fine.  Turns out I wasn't the only one having that
problem.

Those pads also could fade in one stop from 60 MPH.  A set of OEM pads
smoothed everything out for the rest of the years we had the car.
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From: "Randall" <[email-masked]>
Date: Fri, 26 Dec 2014 20:47:34 -0800

>  Can 5 thousands show up in the pedal ??

.005" is huge, if the other side doesn't match it (in other words, thickness variation).  Typical maximum spec is under .001".

However, if the thickness is constant, then .005" shouldn't cause too much of a problem.  The caliper just tracks the wobble without
pulsing the pedal.

>  can a shop turn that much out ??  

Depends on how badly worn the rotor is.  Most cars these days have rotors so thin that they can almost never be turned (once they
have been used) without going below the wear limit.  But I have no idea if that would apply to a Suburban or not.

Randall

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