Why 13 inch Wheels?
05-22-2019, 05:50 PM
#21
Race Director
Simply put a "very sticky" IE hot slick or super 200 tire will feel better on track with the wider wheel.
A 13" wheel will have less sidewall deflection than a 12".
Sharper feel will make you faster.
People have been mounting 18x13's with no problem since a week after the C7Z came out.
Note this is for track use where you are at the limit. For the street a 12" actually is more pleasant to drive.
A 13" wheel will have less sidewall deflection than a 12".
Sharper feel will make you faster.
People have been mounting 18x13's with no problem since a week after the C7Z came out.
Note this is for track use where you are at the limit. For the street a 12" actually is more pleasant to drive.
05-23-2019, 09:29 AM
#24
Le Mans Master
Some things are a matter of fact rather than opinion. Believing that a wider contact patch means less longitudinal acceleration is factually untrue. It's easy enough to disprove. Also, it's easy enough to prove empirically whether a particular tire performs better on a 12" or 13" wheel. I don't think a lot of what's been stated in this thread as fact is...factual. For example, a sharper steering is faster on track: maybe, maybe not. It depends on the driver and car setup. But lots and lots of pure race tires don't have very sharp steering response. The peaky slip angle curve that tends to come with sharper steering response makes it harder to keep the tires near their peak grip envelope. And while it may - may - be true that a tire stretched onto a wider wheel has less sidewall flex, there's more than just the amount of flex to consider. For example, a tire whose section when mounted looks like a rectangle will have equal flex angles for both sidewalls, and keep the tread more parallel to the road as it flexes. Whereas a tire whose section looks like a trapezoid (truncated pyramid, with longer base than upper tread surface) will flex with different angles on both sidewalls. The result could be that the tread on the outside is lifted off the road surface while the inside is pressed harder into it. The point here is that nothing in tire dynamics is simple, and there's no edict that says eliminating sidewall flex is a universally good thing, or that stretching a tire onto the widest wheel it can physically fit on is automatically the best performing setup.
There are tires that work a lot better on 13" wheels, no doubt. The 345 Hoosier is surely among them. But some tires are not designed for that width wheel, and the 335 Rival is a good example. We all use the 315 Rival on 11" wheels, which seems to be ideal fitment. The 335 is less than 1" wider, and has way less than 1" extra tread width...so I don't see the logic in trying to stretch it onto a 2"-wider wheel. When BFG says that tire's max rim width is 12", that should be considered as additional evidence.
There are tires that work a lot better on 13" wheels, no doubt. The 345 Hoosier is surely among them. But some tires are not designed for that width wheel, and the 335 Rival is a good example. We all use the 315 Rival on 11" wheels, which seems to be ideal fitment. The 335 is less than 1" wider, and has way less than 1" extra tread width...so I don't see the logic in trying to stretch it onto a 2"-wider wheel. When BFG says that tire's max rim width is 12", that should be considered as additional evidence.
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froggy47 (05-23-2019)