Date:         Tue, 2 Oct 2001 23:11:28 EDT
Reply-To:     JKrevnov@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rico Sapolich <JKrevnov@AOL.COM>
Subject:      Re: brake noise, etc.,etc.
Content-Type: text/plain; charset="US-ASCII"

In a message dated 10/2/01 9:04:21 PM, EdVF1000R@AOL.COM writes:

<< If your rotors have to be cut, make sure that they have a nondirectional
finish on the working surfaces. Most brake lathes leave a fine spiral groove
on rotors like a vinyl record (remember those?). This causes poor break-in,
hard pedal complaints, rapid initial wear, and noise. >>

If rotors require cutting they also should be checked for runout, variation
in thickness and chatter marks after the machine work is done.  The last time
I had rotors cut, they each varied by .006 inch in thickness from minimum to
maximum.  I do not know if this would have caused a pulsation, although I am
pretty certain it would have.  I also do not know how such a cut can be made
considering the stoutness of the toolholders on an Aamco brake lathe.  Maybe
the operator had not sobered up completely and forgot to lock a toolholder.
Whatever.  Measure twice, cut once.

All lathes leave a spiral tracing as a consequence of how they operate.  If
the rotor is not finished with a non-directional grind, a change in rotor
cutting shops is in order.  If you are stuck with rotors which have not been
randomly ground, you can fake it by going over the surfaces in a spiral
pattern with 60 or 80 grit aluminum oxide cloth.  Should you happen to find
an engine lathe into which to chuck the rotor for this bit of handwork,
you're in like Flynn.  Otherwise, just break out the elbow grease, it only
takes a few minutes per side.  Since we are the Land of More is Better,
forget about using the belt sander, disc sander or anything of that sort.
You want to refine the surface, not redefine it.

Rich