Bob F actually wrote:

+ The engine delivers ~25% less driving force to the wheel contact patch

That's crazy! Where on earth did that come from. 1" diameter increase
would only cause that change if you started with 4" O.D. tires.

Maybe I read the article wrong that was referenced by Ed Pawlowski?
https://www.carthrottle.com/post/how...t-performance/


Low profile tires compensate for the wheel diameter increase, so no
increase in tire diameter occurs, and no torque loss should occur.

+ Which results in a decrease in acceleration
+ And which decrease in fuel economy (presumably at all times)
It should increase economy. Just like driving in a high gear does.

I understand your intuition, which is the same intuition we all have but if
it's true what that article from Ed says, then 25% less torque at the
contact patch means 25% less torque to combat increased wind resistance at
highway speeds.

That means, in the words of the article, the engine has to 'work harder' to
combat that wind resistance.

You tell me how making the engine work (presumably a lot) harder increases
fuel efficiency.

My understanding is that low profile tires are being used because they
have lower rolling friction - the rubber is flexing less, so there is
less loss to heating the tire.

Neither of the two articles mentioned that factor.

And unsprung weight goes up by a few pounds

The main astounding number is the fact the torque felt at the wheels is
astoundingly less for a single inch in overall diameter change.

Yes, it is astounding. In fact, I would suggest it is unbelievable.

That's a fair assessment since 25% less torque for a one-inch increase in
diameter is astounding.

Can you take a look at the article to see if I did my math wrong?
https://www.carthrottle.com/post/how...t-performance/

360 Newtons is 78% of 460 Newtons.
460 Newtons is 128% of 360 Newtons.

That's roughly 1/4 if my math is right.
(I never know which direction to quote but both end up being about 1/4.)