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Summery about ? on Rear Brake Drums

To: submit <triumphs@autox.team.net>
Subject: Summery about ? on Rear Brake Drums
From: J&E <ebk@buffnet.net>
Date: Mon, 10 Jan 2000 08:49:30 -0500
Hi List!
        Here are my questions asked to the list:

Subject: Rear Brake Drums  interchangablity?

Hi List!
        Since the topic of AL. Fin Rear Brake Drums, off of a 240 ->
280Z, has
come up, I have a question on interchangablity. Is the TR6 Rear Brake
Drum interchangable with the TR4/A IRS Rear Brake Drum? 
        Please correct me if  I'm wrong: The TR4 Rear Brake Drums are
interchangable with the TR4/A Rear Brake Drums, & the TR4/A IRS Rear
Brake Drums are interchangable with the TR4/A Rear Brake Drums. TIA
 -Cosmo Kramer
------------------------------
Subject: Legal wear on drums?

Hello List again!
        Another question popped into my head reguarding AL. Fin Rear
Brake
Drums. I have learned that the AL Fin Drum has a steel lining inside the
drum. Which makes sense. My question is: if one is to obtain a used set
of AL Fin Drums, then how does one know if the are reusable? or If
turned down beyond "safety" spects? I shall post any "off line"
responces back to the TR List. TIA -Cosmo Kramer
============================
These are the "off list responses that I said that I would post to the
TR List:

#1- Subject: RE: Legal wear on drums?
        Date:    Sat, 8 Jan 2000 12:24:25 -0600
        From:    "Ken Gano" <kengano@mcleodusa.net>
    To:          "J&E" <ebk@buffnet.net>

At least on the 240Z drum, there is, cast into the inside, spec's re:
minimum diameter.  -Ken Gano
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#2- Subject:    Re: Legal wear on drums?
    Date:               Sat, 08 Jan 2000 11:59:10 -0800
    From:               Randall <randallyoung@earthlink.net>
    To:                 J&E <ebk@buffnet.net>

Cosmo :
The only way to know for sure is to measure them.  I don't have a 240Z
manual handy, but I'm sure you can find one in the library.  The best
way to measure is a special tool for the purpose, but you can sometimes
'make do' with a 12" dial caliper.  Any shop capable of turning drums
should be willing to measure them for you (but of course that means you
already got the drums).

I suppose another possibility would be to make a 'no-go' gauge
consisting of a length of steel rod with the ends rounded and ground to
exactly the maximum ID of the drums.  -Randall
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#3- Subject:    Rear drums
    Date:               Mon, 10 Jan 2000 11:05:11 +1000
    From:               Peter Wilson <Peter.Wilson@vsl.com.au>
    To:                 ebk@buffnet.net
    CC:                 triumphs@autox.team.net

Hi Cosmo/list,
With respect to the various messages on this topic, I have put 240Z
drums
on my TR6, and may be able to shed some light.

1) These drums would fit any TR using the TR6 stud pattern and using the
9"
drum . This includes all TR4's, TR4A's and of course TR5/250. All
applications will require opening out the central hole and countersunk
retaining holes (optional). Stud holes would also need to be opened-out
for
live axle cars.

2) All 240Z's had finned aluminium drums with a cast-in iron liner.
Don't
know about 260Z's and I suspect that rear discs were used by the time of
the 280Z. However, due to their uniqueness and popularity, you may find
that a 240Z has lost its alloy drums and had them replaced by solid iron
items off a lesser Datsun.

3) The iron liner is not replaceable.

4) The 240Z drum has a maximum permissible diameter cast on the inside.
>From memory, this was about 230mm (or 55 thou) over the nominal size. Mine
did not clean up when machined until about 70 thou over. This is not a
safety problem, as the cast iron liner is very thick. What it does mean
however, is that you cannot use standard brake linings. Any reputable
brake
shop will be able to bond some thicker linings (to your standard TR
shoes)
and then "radius" these to match the new drums. I did this with mine and
they bedded in very quickly and have worked fine ever since for both
fast
road and some track work.

5) Good luck finding some healthy 240Z drums. They do tend to corrode
onto
the hub and will come off in pieces if a heavy hand is used to remove
them!

Regards, Peter Wilson
/////////////////////////////
        I whant to thank everyone for they time & effort to responding
to my
questions about Rear Brake Drums. Wether you answered on or off the
list.
-Cosmo Kramer

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