> From: jey@frame.com (Jeff Young)
>
> I've got a '65 Ginetta G4 that I'm taking vintage racing when I finish
> restoring it. It's got a Spridget live rear axle with 7" drum brakes.
> Or at least they normally do (that is, the ones that didn't have the
> Ford 10 rear axle).
>
> Mine's got the Spridget axle, brake backing plates, and brake drum.
> All the internal brake bits are Spitfire. The top of the backing
> plate had a big rectangle cut out of it, and the corresponding piece
> of a Spitfire plate welded in. A couple of holes were drilled for the
> shoe retainers, and all the Spitfire internals were substituted.
>
> Now if *I* had gone to all this trouble, I would have at least
> upgraded to 8" or 9" drums, but who am I to say. I can only
> conjecture as to why someone else did it:
> - the front suspension and brakes are Spitfire, and they wanted
> everything consistent?
> - the Spit wheel cylinder has one less seal to leak?
> - something else is better about the Spit internals?
> - they had Spit stuff on hand, and the brakes that came with the axle
> were dead?
First, why was this done? Was it on a race car from some time past or was it on
a street car that you have decided to vintage race?
Assuming it is an old race car, it is possible that either the brakes were
changed because there was an advantage to using the Triumph Spitfire parts (like
better brake material, better cooling, etc) or a large supply of parts and the
rules permitted a change of materials without allowing a change in size (no 8"
or 9").
-or-
changed because they were better again like before but they were illegal to do
so and thus were hidden inside the legal-appearing 7" drums.
> Can anyone postulate on whether or not I might have trouble with this
> system? The welds look to be quite solid (although I didn't X-ray or
> Magnaflux them).
Best guess would be to inquire with the person who own the car and drove it this
way. After all, you own it now, so he doesn't have anything to lose by telling
you they stunk if they did or gain by saying that they were great.
> I might want to pursue. Do aluminum brake drums have iron inserts for
> the friction bearing surface, or do the shoes ride directly on
> aluminum? If so, do they use a different pad? (It seems like
> aluminum would gall up most any friction surface.) Does anyone know
Aluminum drums were iron on the inner lining on most cars so I'd see no reason
they are not on this one. Aluminum would gall the brakes like you said.
Advise?
In vintage racing, most groups use the 7/10ths rule and the 13/13 rule.
The 7/10ths rule means that you drive to 7/10ths of your ability and the cars
ability. If the car can do 100, you do 70. If you could take the corner at 50,
you take it at 35.
the 13/13 rule has to do with make a mistake and you go on 13 months probation.
Make another and you go on 13 months suspension.
combine these two and it says that you should be very careful and not nearly as
fast as you think you could go. So you should be able to take even a system out
there that may not be the greatest (like a good street system) and still be able
to run. Just don't crowd anyone and don't try pushing the limits. Leave lots of
room to stop and slow down. If the brakes work ok, then you can slowly push
upward toward that 7/10s.
Best advise is take them to an autocross, where you can try them with some speed
and see if they work, without worrying about hitting something or someone and
without worrying about cops.
If you don't feel comfortable about them, take them to someone who understands
brakes (we aren't talking Midas here) and discuss honestly what you are doing
with the car.
Doc m.cobine@genie.geis.com, 70373.2450 on Compuserve
ASR #77 Corvette, Chicago Reg. Nat. Comp., Div. F&C, Reg. Sound, Crew
^^^^^^^
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