Well it undoubtedly happened during a race. You ain't driving that car on
the street.
I don't think you're going to have real problems with the drum, even when
you see cracks like that. The cast iron is just for friction--it's not all
that structural. Cracks are common in aluminum drums with cast liners
because the aluminum expands so much when it's hot. You could make a point
for pre-breaking liners to reduce the risk of them distorting the drum or
separating from the aluminum.
Back in the good days of iron mechanics and wooden motorcycles we had huge
double-sided four leading shoe drum brakes on the front of racing bikes.
The leading shoes, tight courses and high speeds pumped a lot of heat into
the drums. The linings cracked like crazy and we ignored them--mainly
because a 210mm 4LS brake cost a small fortune and we never wanted to
replace them. I don't remember any failures, even though some of them
looked like jigsaw puzzles.
Of course now that I've said that my back wheels are going to fall off.
-----Original Message-----
From: Jack W. Drews [mailto:vinttr4@geneseo.net]
Sent: Tuesday, June 17, 2003 1:43 PM
To: fot@autox.team.net
Subject: brake drums
My TR4 race car has Datsun 280Z rear brake drums.
This morning I removed and inspected them, and found that one of them had
three cracks across the iron friction face. Yuk. I have used these drums
for five years and they never even needed turning. I inspected them last
winter and did not see cracks at that time, but maybe they were there and
I
didn't notice them.
At any rate, be forewarned that this kind of failure can occur. The
thought
of it happening during a race is not pretty.
uncle jack
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