I am given to understand its to stop the material breaking up around the
outside because its still thick enough to hold the rest together.

Not that I know a lotabout cars, but that seems to be the reason people are
given.
Brian

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"Jim GM4DHJ ..." wrote in message
news

"DerbyBorn" wrote in message
2.222...

Why don't they make the pads just a bit bigger so that they don't allow a
lip to develop on the periphery of the disc?

so mercedes etc can sell you discs ......