Quote:
Originally Posted by RobertSmalls
The Potenza RE92 165/65R14 are rated for use on 14" rims, 4.0" to 6.0" wide. Stock rims on the Insight are 14"x5.5", and the spare tire has an alloy wheel, 14"x4.0". What would happen if I got four spare wheels and mounted real tires on them?
I reckon the answer would be "larger circumferance, smaller contact patch, less traction". But would the differences be noticeable, and would there be less sidewall flexion and rolling resistance?
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Using a narrow rim tends to arch the tread surface of the tire. The published allowable rim width range keeps the arching to a minimum.
But it is a misconception that the sidewall is what controls the amount of flex. What is really resisting the load is mostly in the tread area - and in particular the steel belts. The sidewall flexes, but doesn't contribute much to resisting the load.
So using a rim on the narrow end of the range isn't going to change the amount of RR, becuase the same amount of "tread" (both the tread itself and the steel belts) are being engaged.
What might happen is that the pressure distribution on the tread surface will change to more pressure applied to the center - and this might result in some wear issues. But the big thing would be the tire would become more sensitive to road surface irregularities - it will try to follow the grooves and the ruts in the pavement.
Plus many spare rims are built thinner - and that makes them less durable, prone to cracking.