Re: Part/repair advice wanted

[Toby Basiliko <toby@Wolfenet.com>]

Steve,
  I won't tool on you for what someone else said, but I don't buy it. 
I've had brakes with 20,000 miles on them start squealing.  Long after
any cutter marks are gone.  
  But I bet his trick often works, for it would cut glaze off the rotor,
which would in turn cut glaze off the pad.
  Whaddya all think?
Toby B
(currently with drums, anyway!)
> 
> This note on squeeling disc brakes. A local auto repair radio talk show in
> Atlanta has a mechanic named Sam Memmolo on it. He says the reason disc brakes
> squeek is that the rotors have probably been turned using a directional cutting
> tool (the kind on just about every brake lathe in mechanic shops).
> 
> These directional cutting marks cause the pad to "dance" on the surface of the
> rotor when pressure is applied, thus causing them to vibrate against the pad
> holders and make a noise. The cutting marks can also cause new pads to
> prematurely fail, depending on the type of pads used.
> 
> He says the original cut on the OEM rotors is done using a helical cutting tool (
> makes curved cutting marks across the face of the rotor instead of parallel to
> the direction of rotation of the wheel).
> 
> He comments that you can smooth down these cutting marks by mounting the rotor,
> spin it and sand it with 320 grit emery cloth, moving the paper back and forth
> from the hub to the outer rim of the rotor to remove the directional cutting
> marks of the brake lathe. He says the smoother the surface, the less the squeel.
> 
> Steve B.