Posted by Roger on September 27, 1999 at 14:16:27:
In Reply to: tire diameter vs width influencing fuel economy posted by Bill Austin on September 24, 1999 at 06:35:53:
Sorry but the true answer is not available as there are just too many other variables.
A change in size does have an effect in Rolling Resistance but tires are only about 10 to 20% of total fuel economy so it would take a major change in RR to see a change in fuel economy.
I will even point out an error in your basic assumption. If you put a taller tire on the car you will go more miles for the same number of engine revs which would imply improvec economy. But you also have increased the air drag because the vehicle is now "bigger" as far as the air resistance is concerned so this reduces the fuel economy at higher speeds.
See why it is complicated and we didn't even get to the different brands of tire or tread compound or tread design or inflation pressure or alignment etc etc etc.
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