Quote:
Originally Posted by CapriRacer
I think the "wider is better" works regardless. Look at it this way,
If RR is energy loss - and the energy is lost in form of heat by the internal friction of the tire and the friction with the road surface plays a minimal role - then most of the heat is generated within the tread rubber, because it is both the largest mass and because it is deflected the most. Sidewalls have a much smaller mass and depending on where on the sidewall you look, they are defected as much as the tread.
That means the ply materials, such as polyester and steel don't have a very big impact on RR so replacing them doesn't result in much difference. But changing the tread rubber does.
Also, the amount of deflection is controlled by both the inflation pressure and the load. So going to higher inflation pressures gives you better RR - and going to a lighter load gives you better RR.
In fact, RRC (Rolling Resistance Coefficient), where RRC times the load on the tire = RRF (Rolling Resistance Force), is fairly linear and not dependent on how close to the rated load you are. You could be above it or below it and the RRC is still fairly linear - and for a given inflation pressure, the same value.
While as a tire engineer, I am happy that is so - keeping people safe should be my first priority - that doesn't change the laws of physics. It's just the way it works.
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Capri
I always try to embrace all opinions.
However
Orig poster went from 15 to 17 to decrease mpg
Do you own and familiar with that particular vehicle
really not seeing the basis in experience that going
from 185/65R-15 to 175/65-15 would decrease RR,MPG, and performance.
What I think may happen is one of two which is changes nothing or possible improvement.........
I also have found a tire dealer who would mount the tire.......