Came into this discussion late, have been away from computer. The following
is a compilation of comments regarding the Al-fin drum substitution that I
have saved over the past couple years (wish I had kept the dates intact).
It does include some that were posted in the last few days, but thought it
might be helpful. I have included the name & email address of the
"respondent". Hope you guys don't mind. Addresses may be outdated on some
of them.
Carl Musson
Tampa, Florida (USA)
TR3A's - 1958 Driver &
1960 Concours d'wannabe
http://www.arts.usf.edu/~musson/triumph/
"You can't tell which way the car went by just looking at the road..."
Subject: TIPS: Al-fin brake drums on TR3
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 aluminum 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
Peter.Wilson@vsl.com.au <mailto:Peter.Wilson@vsl.com.au>
<mailto:Peter.Wilson@vsl.com.au <mailto:Peter.Wilson@vsl.com.au> >
==============================
I sent out the original answer to the question regarding Datsun
brake drums on the TR's.
I have them installed on my vintage TR4 racer and they went through
40 hours at racing speeds this summer. At least six fellow racers in my
circle of friends also use them. You really don't have to believe me when I
say they fit. That's your choice in a free country. However, for those
who choose to believe me, or for those who missed it last time, I will
repeat the list of minor alterations necessary to make them fit:
1. Bore out large center hole to same diameter as protrusion on TR
hub
2. Ream out wheel stud holes to fit the stud shoulder
3. Machine the groove at the outer diameter into which the backing
plate flange fits - 1/8 inch larger diameter, 1/8 inch deeper.
4. Machine 1/8 inch off of the width of the steel insert on which
the brake linings run
Cost of my drums was $10 apiece. Machining sounds complicated when
described in words but is really not. My cost was $35.
This retrofit works for TR3, TR4, TR4a, TR6, etc..
Peter Zaborski
Peterz@merak.com <mailto:Peterz@merak.com> <mailto:Peterz@merak.com
<mailto:Peterz@merak.com> >
==============================
We are working on a TR6 for autocrossing, and have a set of 240Z drums to
fit. The center hole needs a few mils shaved off, and the retaining screw
holes must be drilled and countersunk (we will take them to a machine shop
rather than risk ruining them). The difference in weight is significant (~5
lbs), especially considering this is unsprung weight that affects handling
more than extra weight on the car's chassis. Hopefully the fins will help
with cooling, but I can't imagine they would be worse than stock. Besides,
the rears aren't worked nearly as hard as the fronts. Hopefully, the car
will be on the road within two months and I can report on actual use.
Joe Seward
'73 TR6
==============================
A fairly recent Grassroots motorsport article (on their web archives
at http://www.grmotorsports.com/boneyard.html
<http://www.grmotorsports.com/boneyard.html> suggests that aluminum finned
brake drums from a Datsun 240Z is a worthwhile swap. Is the advantage
merely better cooling? Are the finned aluminum drums significantly lighter?
The article also mentions the Datsun drum centers have to be bored out.
I know from my dad's experience with T-series MG's that the Al-Fin
drums for them are very pricy. The 240Z drums are cheap enough that it
seems every Datsun 510 being driven competitively has them on.
---
Ted Stevens
stevens@erols.com <mailto:stevens@erols.com>
==============================
My understanding is that the main reason for using them is the weight
savings (they are apparently allowed in VARA stock classes, as substitutes
for the factory Alfin drums). Since the Datsun drums are apparently not
Alfin (which refers to a trademarked method of bonding iron to aluminum for
improved heat transfer), they may not cool any better than the iron drums.
The 10" drums used on earlier cars would probably provide better cooling
than either 9" setup, but they are heavier yet (and apparently not currently
available).
Randall Young
randallyoung@earthlink.net <mailto:randallyoung@earthlink.net>
==============================
I wrote a while back asking about what I understand is/was a popular
modification, fitting Datsun 240Z finned aluminum brake drums.
I ended up getting a set at a reasonable cost. I then *carefully*
used a drum sander to remove about 0.5mm of material from the hub center
hole, stopping frequently to test fit. After just a few minutes, a perfect
fit!
... on the right-hand side.
It seems that on my car, the brake backing plate/dust cover on the
left hand side is ever so slightly larger than that on the right
hand side, so the Datsun drum, which has a slot to receive the lip of the
backing plate, doesn't fit on the left. Looks like I have to machine out
the slot a bit.
I do think that it'll be a neat modification whenever I can get the
work done - less rotating mass, better cooling, and sharp looking.
For those of you with brake backing plates that match and are the
right size, this should be a really easy swap.
---
Ted Stevens
stevens@erols.com <mailto:stevens@erols.com>
==============================
The biggest thing that NEEDS to be done(won't work without this) is to thave
the center hole enlarged. The datsun center hole is about .080" smaller
than the triumph center, the drum will not fit unless this is done. The
retaining screw aren't a big deal and you don't need to worry about IMHO. I
don't use them and I don't have a problem. You do not need to do anything
to the stud holes, they are fine as they are. If you do decide to paint,
flat black is the only option for heat transfer, but I do not have mine
painted. Also since I assume these are breaker yard drums, have them check
for runout, you don't want pulsating drums.
hope that helps
Aaron
SpitRacer9@aol.com <mailto:SpitRacer9@aol.com>
==============================
Make sure the center "big hole" is the correct size. The brake drum
"centering" is the most important aspect of this job. If you need to open
that hole up, bring the drum and a hub to the machinist to get it right.
Think "hub centric".
Well, you might be able to get by without opening up the stud holes
since your TR6 comes with pretty wimpy 7/16th inch lugs. On my 260Z brake
drums, the holes just needed a little "chamfering" on the back side. Of
course then I installed ½ studs so then I had to open the stud holes up a
lot.
As for the retaining screws - you don't really need them, but if you
insist - go for it.
They look nice if you bead blast them... but before you do anything
make sure the ID of the brake surface does not exceed 9.055 inches, at least
that's what's cast on my drums. You might also want to "crack test" them.
Of course turning/crack testing should be done first.
;-)
Do Not paint. These babies get HOT.
Robert M. Lang
lang@ISIS.MIT.EDU <mailto:lang@ISIS.MIT.EDU>
==============================
Aluminum brake drums will be easy to identify. Aluminum doesn't rust.
(Well, aluminum does oxidize but aluminum oxide isn't red but white.
Anyway, the aluminum drums will have aluminum on the outside where it
disipates the heat generated during braking. The friction surface is steel
(since the aluminum would wear too fast) but much of the rest is aluminum
and will look greyish-white.
Good luck. There are not lots of 240Z's in the yards that I have seen.
Dave Massey
105671.471@compuserve.com <mailto:105671.471@compuserve.com>
==============================
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