Jack:
Having raced 240Z's for some years with rear drum brakes, I can say your
problem is not an isolated one, however it has not usually been cause for
concern in a race. I have taken many drums off with cracks and clear
evidence of heat, but never actually had the ferrous linings come adrift.
They are especially subject to cracks as they get close to their maximum
size, the dimension for which is typically cast into the aluminum on the
face.
240Z's in the Improved Touring S-class tend to have a bit more grunt than
the brake system is designed for, so to assist the overworked fronts, you
try to bias as much to the rears as you can handle from a driving
standpoint. That usually involves high friction linings for the rears and
attention to bleeding and adjusting out the rears frequently. You end up
replacing a lot of shoes, and the drums don't last too much longer than the
shoes, especially if you take them out of service somewhat before they
enlarge to their maximum dimension. It is a maintenance intensive approach,
but they do work, and the drums are available through various supply houses
for not a whole lot of dollars. Ventilating the backing plates as well as
heat-dispersing coatings on the drums seem to make things last a bit longer.
Maybe others have different experiences with the potential hazard of the
cracks, but I've never seen a Datsun drum cause any real problems. I do
seem to remember Hardy being very attentive to his drums, of course Hardy
lavishes lot's of attention on most everything .
Dave Talbott
----- Original Message -----
From: "Jack W. Drews" <vinttr4@geneseo.net>
To: <fot@autox.team.net>
Sent: Tuesday, June 17, 2003 1:42 PM
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
|