[Shotimes] Tire/rim width

[Leigh Smith]

The old thumb rules still hold up pretty well. However there are 
specific manufacturer's recommendations for suggested rim width, for 
each size tire. BFG and Goodyear both do a great job at this and have 
tire info posted on their websites.

There is another major issue with wide tires on the SHO, wide wheels. 
True a 8 inch wheel would support an 8 in tire ideally. But the tire 
sidewall dimension grows as well. That "thumb rule" is "add 0.5 in. to 
sidewall width for every 1.0 in added to wheel width". This means you 
need to know the "spec rim size" that the mfgr uses to come up with his 
sidewall dimension. It's in the flyers. A 8 in wheel may make the 
sidewall dimension grow as much as 1 inch.

IIRC, and the reason I bring all this up, is that the major limiting 
factor on tire width on a SHO is sidewall clearance. Mine is 1/2 in. 
(Max) away from the swaybar link "BOLT". with stock size tire/slicers. 
IIRC someone had a stock size tire blow-out at high speed on the race 
track during an earlier Atlanta convention due to rubbing this bolt and 
tearing out the sidewall. There can be a lot of sidewall movement under 
high loads with tall 60 series sidewalls.

Ian F. has 8 in wheels and 225/55 tires (or /45), but I believe his 
offset is not stock, it is outside a little bit. He has the same bolt 
clearance as stock, but the tire sticks out the fender lip 1/4 in. If he 
were to go to a stock offset to tuck the tire in, he'd tear the sidewall.

My 0.02 advice, deal with the real threat and sawzall off half the d*** 
sway bar link bolt. There is at least another 1/4 - 3/8 in or so til the 
tire rubs the smoother strut. Go with 7-1/2 to 8 wide, and tuck them way 
in with the right rim offset.

Lee
"I put 10 in wide wheels inside the stock fenders on a 70 Z28 when 
everyone said it couldn't be done"



dean james wrote:

> I had to go out to the parking lot in 100+ degree heat and take some 
> measurements. (109 degrees yesterday!)  Both sets of my Yoko 225's 
> have a tread width of about 7 5/8" which would be 194mm.  So these 
> tires are right at the limit of tread width 1" larger than rim width, 
> and an 8" wide rim should be good.
>
>> Equate terms like "the old rule" to "old wives tales".
>>
>> If in doubt, go to the Tire Rack Spec site for the particular tire 
>> and size
>> that you are looking at. That will tell you what the mfr feels is the 
>> best
>> setup.
>
>
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