RALLYE
USED BRAKE DRUM INFO - page
1 of 4
Why
all this writing? Determining what is a "good" used part
or a "bad" used part is debatable. I could just sell used
drums with no comments. I think it is better for you to
know what is what when you are looking to save a buck in
your repair/restoration.
You
have to remember that old cars are dangerous. They can
kill you. Driving them; working on them; they are not
2016 vehicles; they aren't as safe. This is something you
need to accept if you have an old car. They're definitely
more fun, like rock climbing or cycling or any other
endeavor we undertake other than hiding under the bed.
Used parts are used parts; they are old; they can break;
they can fail. New parts can have defects as well; and
once you mount it on your car; your "new" part is now a
USED part.
Don't
quote me on any of this as I am not a brake engineer. Use
these facts, opinions and conjecture at your own risk. Do
your own research; form your own opinions; I am only
reporting what I have observed in 44 years of playing
with these roadsters. Take any information on this page
with the proverbial grain of salt. I tried in the 70s to
get "official" specs from Nissan on the minimum thickness
of the rotors, ball joint clearance maximums etc.; and
was never successful. One of the letters I received that
I wish I had kept and framed said something like "They
should be replaced when worn to a suitable
amount".
Drums
too thin can have strength and heat retention issues
leading to warping, cracking and brake fade. (I've never
seen a cracked one.) Also; the more the diameter is
increased; the more the curvature (arc) over where each
brake shoe contacts the drum is altered. Eventually; the
shoes are only making contact in a limited area of the
drum. In the past this was handled by "arcing" the shoes;
a procedure done by automotive machine shops or some auto
repair facilities. This isn't done much anymore unless
the shop has specialized equipment to handle the release
of possible asbestos laden brake shoes.
As
a result; the braking done by the rear wheels is reduced
somewhat. The shoes will wear faster in certain areas but
will "fit the arc" better after some time. A single
cylinder system as found on the rear of the roadster
doesn't work properly anyway; compared to a dual cylinder
setup. We are also talking about a VERY small difference;
as even a plus .060" diameter drum is only .030" larger
in any specific area of the drum. Also keep in mind most
of the braking action is done by the front brakes.
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