In a message dated 6/2/04 6:30:10 PM Pacific Daylight Time,
b.a.savage@earthlink.net writes:
> Are "hard spots" real hard?
> Doesn't it require grinding the surface?
> My OEM rotors only have 0.075 left. (0.005 wear). Doesn't seem like
> much..!.?..
>
>
Yep...those shiny spots are harder than the dull metal and the pad scuff
across them differently and creates a vibration. The hardness is no where near
as
deep in the metal as the shiny spot is wide and the rotor has to be thick
enough to be machined deeper than the hard spot, usually a few thousandths.
Each
rotor has a "machine to" spec and a "discard" spec as put forth by the
manufacturer of the vehicle. If there's not enough metal left to cut both sides
of the
rotor below the hot spots it's a throw away. Most quality rotors will be
thick enough to be machined like this about two brake jobs before they get to
the
limmit. Some real cheap rotors are manufactured only a few thousandths above
the machine to limit. You can't go wrong putting on new quality rotors instaed
of machining them. Raybestos makes quality pads and rotors
and if they were clean and torqued right, and if you're not trying to stop
the Queen Mary you'll be fine. If you're ever going to have them machined it's
perfectly acceptable ........find an experienced brake shop where they can read
a michrometer and read the hot spots too.
doc
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