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Old 06-11-2008, 09:42 AM   #113 (permalink)
CapriRacer
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Quote:
Originally Posted by tasdrouille View Post
That aint quite so.

RR = RRC * load

You've got a car applying a load X.
You have P215/70R15 with a RRC of roughly 0.0099.
You have P195/65R15 with a RRC of roughly 0.0113.
Both tires can handle load X.

Which tire has the lowest RR?

EDIT:

Where exactly do you see rated load in the RR equation?

This gets back to the issue of confounding:

A P215/70R15 has a Load Index of 97 and an OD of 26.9" , where a P195/65R15 has a Load Index of 89 and an OD of 25.0"

What this means is that a P215/70R15 would never go on a vehicle where a P195/65R15 is specified and vice versa.

As you have noticed, the RRC goes up as the Load Index goes up, but this isn't useful in dealing with an individual vehicle (unless you are either designing one from scratch or extensively modifying an existing one) As a general rule, a given vehicle is pretty much constrained to take tires within a small range of LI's.
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