Peter, the magnet is a great idea if you are specifically looking for
aluminum. I really don't know if the 240Z drums came in *both* alum. &
steel castings. ISTR it was only in alum. But the memory ain't what it
used to be.
But, assuming the radially finned casting is aluminum, I'm sure you will
still find a steel insert inside, where the shoes ride. I believe this
may be replaceable if/when the drum is worn out, so the outer casting is
reused (provided you can find parts and folks who know how). The insert
is what you would have turned to true up the drum if needed. So, you
might want to use a weaker magnet for your test and do your test on the
extreme ends of the fin radius, or the magnet might pick up on the steel
inside the drum. P.S. if you find an *extra* set of drums at a great
price, drop me a note! I intend to do this on my 4, to, but it's not
high priority... however, if a great deal comes along... ;-)
In case it is helpful to anyone on the list, just checked a new TR4
rotor in the garage & it is marked min. thickness 11.3 mm, which I
believe converts to .44 inch. Since it's new, I measured the starting
thickness & found it is .505, which means you have .065 of wear allowed
over the life of the rotor. I am guessing that TR3 through TR6 are
probably about the same. May be diff. for some of the other Triumphs out
there.
The min. thickness on this rotor (Brembo) is stamped into the outside
rim. I've also seen it cast into the hub area of the rotor.
As an aside, a friend of mine just had the rear brakes on his XJ6 DHC
rebuilt... get this, he tells me the rotors are welded onto the axle at
the factory & the whole assembly has to be replaced! Bet that was way
expensive! He wouldn't say. Makes me really appreciate Triumph's tried &
true design simplicity!
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
Peter Zaborski wrote:
>
> This topic comes up occasionally on the list, namely that the brake drums
> from the early 240Z were made partly of aluminum and are a pretty reasonable
> fit on a TR6 <http://www.grmotorsports.com/boneyard.html>. Does anyone know
> how to tell if a drum off a junked car is actually aluminum or all cast
> iron? I would like to do this at the junk yard so keep in mind I won't have
> every tool from the garage with me. Is a magnet adequate? (ie. it clings to
> cast iron but not to aluminum, right?).
>
> Thanks for any suggestions.
>
> Peter Zaborski CF58310UO
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MZ
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