Summer tires year-round in San Francisco

[coleAK]

And yes as for the rim diameter questions. Smaller diameter rims: better acceleration, more comfort, better economy (eRange or MPG), better breaking (although ^^^ quoted article says otherwise for breaking, larger rim =more rotational mass). Larger rims: better on the skid pad, and according to today’s mass market standard look better.

Most road course race cars run 17-18” rims. The 911 GT3 cup car - really the standard for a somewhat mass production “race car” comes with 18” rims.

 

[TT97]

And yes as for the rim diameter questions. Smaller diameter rims: better acceleration, more comfort, better economy (eRange or MPG), better breaking (although ^^^ quoted article says otherwise for breaking, larger rim =more rotational mass). Larger rims: better on the skid pad, and according to today’s mass market standard look better.

Most road course race cars run 17-18” rims. The 911 GT3 cup car - really the standard for a somewhat mass production “race car” comes with 18” rims.

I was actually surprised about braking as well from the article's result as I assumed the smaller wheel would brake better (or at least equal) as the contact patch would be equal or slightly larger with the bigger sidewalls. I have two guesses for the difference: 1) the bigger sidewall could have more rotational flex affecting braking or 2) the V vs W rating for the tires - not sure how much difference either makes.

 

[miimura]

I think the better acceleration and braking are purely due to the lower rotational inertia of the smaller diameter wheel. Even if the wheel/tire combo has the same total mass, a larger diameter wheel will necessarily have more mass at a larger radius, requiring more energy to speed it up or slow it down.

The factory Michelin MXM4 18" tires have a very aerodynamic profile with the tread noticeably narrower than the wheel. The sidewalls are even aerodynamically blended into the wheels. If you want higher performance on the same wheel and are willing to give up efficiency, go with a wider tread and lower profile combination that will give approximately the same rev/mile. For example, Pilot Sport 4S is also available in 255/40ZR18 with 8.7" tread width and 799 rev/mile compared to 7.8" tread width and 790 rev/mile for the factory 235/45-R18 size. If I'm not mistaken, the wheel is 8.5" wide, so the 255 tire is not too wide.