Tom,
Having raced a wire-wheeled, drum-braked MGA for the past ten years, I have
a couple of comments. Certainly the original 48-spoke wire wheels were
inadequate for a car weighing nearly 2000 lb. But anyone converting to
original factory steel disc wheels must beware: we have seen MANY failures
of the factory steel discs in vintage racing.
IMHO, cast alloys (being stiffer) probably transmit higher shock loads to
the suspension. Most of the king pin failures we have seen on MGA's in
vintage racing, were cars with cast alloy wheels (and wider, stickier
tires). Not all, but most.
The more I see, the more I like my 60-spoke Dayton heavy-duty wire wheels.
They probably flex a bit & cushion the shock to the suspension. They do
break a spoke once in a while, usually no more than two in a single session,
when the wheels are getting towards the end of their useful life (around
30-40 races). That, to me, is a relatively safe failure mode, offering me
the chance to change the wheel before further damage occurs. The factory
disc wheels crack, and the crack propogates very quickly and is much harder
to detect (in the early stages) than a broken spoke or two. We have had a
couple of instances of sudden/complete/catastophic wheel separation with the
factory disc wheels.
There's no perfectly safe solution -- racer beware.
Mark Palmer
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