At 10:47 AM 2/16/2000 -0800, Jonathan Lawrence wrote:
>....
>I have been autocrossing a 93 240sx for the last two years on race tires.
I would like to try my 64 MGB in a few events this year. It has wire
wheels and I am concerned about over-loading them with the forces generated
if I put race tires on them. Any information or opinions on this ?
Yes. DON'T DO IT !!! When I first ran race tires on my MGA I was
generating stress cracks in the steel disk wheels on a regular basis, like
breaking one wheel every second or third autocross date. Two days before
my custom built alloy wheels arived I broke three steel wheels in one day,
with the last one finally flying off the car. With the tremendous traction
that race tires have, I'm sure this treatment will not be good for wire
wheels.
However, if you are so inclined to chance it anyway for one race date only
to test out the excitement of racing your MG on real race tires, then I
would agree, with the following additional advice:
First, be sure the wheels run straight and true and that all of the spokes
are in place and all tight. If the tech inspectors do their job properly
they will not pass a wire wheel with more than one loose spoke. Inspect
them yourself anyway -- do not trust your life to the integrity of the
official tech inspectors. (I can say that, because I'm one of them).
Secondly, you might consider giving the car just a little less than maximum
effort on the first lap.
Third, check the wheels carefully again after each lap with the same eagle
eye and same concern for tight spokes and safety, and if the spokes remain
suitably tight you might consider taking the next lap.
Fourth, if you do notice one or two spokes getting loose after any one lap,
consider seriously not taking the next lap.
While you may well eventually stretch a spoke or two loose in any given
lap, I don't think you will be doing a lot of damage or totally destroying
a wheel in any given single lap. I would not recommend that you continue
to use the wire wheels with race tires for any more than the one autocross
date. If you only have one set of wire wheels this sounds like a lot of
bother to mount and dismount the race tires just for one autocross date, as
well as the significant risk to the wheels. But knowing where the fun is
(hee hee hee) I don't blame you one bit for going to all the trouble.
I don't know where you are located, but if it's anywhere within one day's
drive of northern Illinois I would be ammenable to lending you the MGA with
an attitude for your trial day, so you can at least try it with an MG (of
sorts) on race tires with nice safe alloy wheels. I'm sorry if it may not
be the same compliant suspension qualities (didn't want to say "mushy" in
public did I?) as you may be used to with your own MG, but at least my MGA
with it's stiff sway bar will get around the track in some reasonable
fashion or another with only a little coaxing. Those few of you who have
had a chance to test the track in the MGA with an attitude should feel free
to let Johnathan know that it is at least "feasible". (Already ROTFLMA).
>As a follow up question, do I need a new rear axle housing to switch to
disc wheels? I know that there are different tube type axles for wires and
discs but I am not sure about the earlier banjo type axle that I have on my
car. ....
Yes. With the banjo axle both the axle housing and the half shafts are
about 7/8" shorter on each side of the car with the wire wheel version to
accomodate the length of the wire wheel hubs and still give the same track
width. You cannot use the WW half shafts in the DW axle housing, or vise
versa. Also, bolting WW hub adapters on to the DW axle may cause rubbing
of the tires on the rear fenders because of the resulting increase in track
width. In short, to convert from WW to DW you need to swap out the entire
rear axle assembly as it unbolts from the leaf springs. Fortunately there
are folks who have had a propensity for converting wheel types in either
direction, so if you were so inclined I'm sure you could find the parts you
need with relative ease.
Pleasant motoring,
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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