Sorry for not being specific. Direct Tire in Massachusetts, and the national
chains the Tire Rack, Discount Tires and NTB advise that a 145 or 155 tire
should be used with a 4 inch wide wheel. Direct Tire warns not to exceed a 165
on a 4 inch. 175s are fine on 5 inch rims, but they will typically interfere
with the body work which is also dangerous.
In SCCA racing (solo and road racing) I have seen 175 and 185 tires on 3.5 and
4 inch rims slice, deflate, disintegrate and roll over. I have also seen
accelerated, uneven wear across the tread. I do not believe the 3.5 is allowed
in road racing any longer, but I may be wrong. Based on my own observations and
the advice of the various retailers, I would not put a 175 on a 4 inch rim.
Naturally, if your manufacturer says it works and stands behind it, then go
with it. Who is the manufacturer? I have not seen any 4 inch steel or alloy
wheels currently advertised for the sprites, and I would be interested in
learning about them. Of course you may be talking about wire wheels which came
in 4 inch width from the factory and are still available. Wires are not
allowed in road racing, except in some vintage classes. If you have wires, I
am surprised the manufacturer said 175 was ok. They certainly weren't approved
when the cars were new. Please write back as I am considering 5 inch alloys
for my bugeye so I can move up to 165 or 175s.
Regards,
Bill
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