Join Date: Apr 2003
Location: Cambridge, England
Re: tyre dimensions and handling ?
In the dry, all things being even (compound, construction, temperature etc.):
- The wider 17" tyre will have a larger contact patch and thus yield more grip than the 15" tyre.
- The lower profile sidewall (stiffer) of the 17" tyre will break away faster on the limit of grip, the 15" will "let go" much more progressively.
- The 17" tyre will give a harder ride as there is less spring effect in the tyre (stiffer sidewall again).
- The 15" tyre will heat faster than the 17" so may reach optimum temp. first (they may overheat quicker too).
- Final gear ratio will be around 3% lower given the different rolling circumferences.
I'd not run these mixed unless I was being ver careful. If you must, put the tyre with greater grip on the rear as your grip is normally limited to the front wheels, this way they can only follow the fronts. Putting greater grip on the front could cause dangerous handling effects (especially in the wet). Because of the difference in circumference do not mix side-to-side, unless you want an oval racer the effects could be disasterous and could cause drivetrain damage.
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