Is there a web site that charts what tire width fits what wheel? Not really,
because it varies with each tire and manufacturer. If you are looking at a tire
on the Tire Rack Web site, click on the "Specs" and you will see what the
manufacturer recommends.
In the case of the Kumho V700 225/50-14, they actually say 6-8" with 7" being
the measured rim width. That means they mounted the tire on a 7" rim to take the
listed measurements. So Kumho says a 6" rim is okay but marginal. I prefer wider
rims, myself, but it's just one of the tradeoffs. Victor, you might want to look
for a 4.11 gearset.
Heat cycling tires also varies depending on whether it is a full road-race tire
or an autocross tire. BFG used to recommend heat cycling their Comp TA R1's and
then letting them sit for a full 24 hrs before using them "for real." Autocross
tires have to come up to temperature fast and then they cool down between
rounds, so they have to be able to deal with more heat cycles.
Here's what's going on. When they cook a tire, it is a process called
vulcanizing. The more it is vulcanized, the harder it gets and the less traction
it has, but it also lasts longer. Race tires are only partially vulcanized, so
they are still plenty sticky. As you heat cycle them, it finishes vulcanizing
them. Most street tires never approach the temperatures that you get in racing
(over 200 degrees), so they stay pretty stable.
Road race tires are a bit different than autocross tires. Most are at their best
for about 4-8 heat cycles, then they start to lose some adhesion. If you are a
budget racer, you can get "takeoffs" from the tire dealer. These are tires that
have been traded in by the big dogs after 4-8 heat cycles. We used to get
takeoff 23.0-9.0-15 Goodyear race tires for $30 each; they were $150 each new.
They can take a couple of laps to warm up. They are designed to come up to
temperature more slowly and keep their traction longer at sustained temperature
than an autocross tire. The real hard-core big-bucks racers will only use a tire
one time, but that's extreme. Sometimes they will go out in practice and run a
few laps to scuff the mold release off the tread. You'll hear people refer to
scuffed tires vs. "stickers" which are brand new unscuffed tires with the
stickers still on them.
Also, they sometimes use "qualifiers" which are almost like autocross tires -
very sticky but only good for 3 or 4 laps before they go away. F1 is famous for
this.
One final thought about driving autocross tires on the street - don't! Those
lightweight tires are not built for road hazards like potholes, railroad tracks,
sharp edges, etc. You can bruise the carcass and cause yourself big problems. I
wish I had taken some pictures of the cracks in the inner sidewalls of my R-1's
after 8500 miles of street driving. It was really scary!
Gordon Glasgow
Renton, WA
www.gordon-glasgow.org/garage.asp
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