Cold vs. Hot tires vs. MPG

[gone-ot]

Paper on effects of Cold vs. Hot tires upon MPG: Document Display | NSCEP | US EPA#

But, also notice the 1978 date!

[roosterk0031]

First engine block heater, now going to need to get tire warmers. Might be easier to turn up the radiant floor heat in the garage.

[tortoise]

As best I can puzzle it out, the "hot" test started after the test tire had been run for 22.95 minutes. I see no indication of how hot they got. I wonder what would be optimum. Auto racers put heating pads around the tires before the start of the race. (to increase grip, not to decrease RR)

[Diesel_Dave]

Interesting quote from pg. 6:

The average percent fuel economy improvement of hot tires over tires at ambient temperature is approximately 5%. It was found that this improvemnt does not change with respect to tire type, size, or manufacturer. This 5% improvement is fuel economy on the dynamometer corresponds roughly to a 50% decrease in tire rolling resistance on the road.

I've noticed in the mornings it seems to matter not only what the current temperature is, but also what the overnight lows were. I seem to do better when it was warm overnight. I wonder if that's because the road temperature heats up the tires more quickly.

I wonder how much of it is due to in increase in tire pressure. I also wonder how much of the total rolling resistance is due to the tires, vs. drivetrain friction.

[euromodder]

5% difference in favor of the warm tyre - but obviously only while the tyre warms up.
And a study dating back to the days of Flintstone-compounds.

[F8L]

This is similar to how rolling resistance is reduced as ambient temperatures increase. I forgot where that paper went but to paraphrase the findings, rolling resistance can double when temps are reduced from approx. 100F to 32F or something along those lines.

[JRMichler]

HMMMM. Anybody want to try a new mod? Quad exhaust aimed at the tires?

[gone-ot]

Originally Posted by JRMichler

HMMMM. Anybody want to try a new mod? Quad exhaust aimed at the tires?

...makes you wonder if the NASCAR guys were onto something with having their exhaust pipes exit directly in front of the rear tires? Didn't help the fronts, but certainly "warmed-up" those rears for acceleration properties (think drag-race "burn-outs" here).

[jakobnev]

I'll be doing this each and every time before driving off from now on:

http://www.youtube.com/watch?v=DQosfF2m7wE