Roland Dudley writes >
>Is it generic (i.e. tire width = rim width/.75) or is the .75 dependent
>on other factors. I currently have 205/15s on the snake's 6" rims but
>will be replacing these very tall tires with lower profile rubber. How
>do I calculate the maximum effective width tire that can be mounted on 6"
>rims?
The industry standard for measuring section width requires that the tire be
mounted on a rim which is 70% of the section width. Yes, I know this sounds
like circular logic.
The industry-standard measuring rim for a 205mm tire is thus 143.5mm or 5.65"
Generally, for sporting use, I would not want to put a tire on a rim that was
less than 70% of the section width. Therefore, a 6" wheel is adequate for a 205
at 75.4%. The widest tire I would want to put on a 6" wheel would be a 215, as
that would be right about 70.9% This is OK, for street use, IMHO, but I would
want more rim, less tire, for autocrossing. I am planning on using 185-60-13
on 6" rims on the Europa for autocrossing. This is 82.4%, which I consider a
good area. At the extreme, I don't think you would want to go past 100%.
Although the actual section width would move out to still be a bit wider than
the rim, I think it would be pushing your luck to put a 155 tire on 6" rim
(98.3%).
A 298 Cobra is comparatively heavy and powerful car, so 205-60-15 sounds like a
good size to me. The 215s may not really give you any more cornering power.
Anything wider than 215s would probably be a waste of time.
If I were you, I would get 205-60-15 BFG Comp T/A R1 tires in the road racing
coumpound. They are probably cheaper than any other decent tire, and they
will stick like glue.
Phil Ethier, THE RIGHT LINE, 672 Orleans Street, Saint Paul, MN 55107-2676
h (612) 224-3105 lotus@pnet51.orb.mn.org (infrequent mail checks)
w (612) 298-5324 phile@pwcs.stpaul.gov (lists go here)
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