Low resistance tire in the rain

Clear, consumer friendly ratings of a tire's LRR or efficiency is not a requirement in the US as it is in Europe, so it is difficult to know which tires are LRR and make a selection.

Nearly any new tire will result in lower fuel economy as a new one's rolling resistance is at its worse until there is at least few thousand miles of wear on them. The corollary to that is the old, worn tires just replaced, where providing the best efficiency numbers seen by the car.

 

That may be, with some tires, and sounds very plausible. I did have one experience though, coming from well worn Bridgestone Insignia SE200_02 (LRR OEM), to brand new Bridgestone EP20 (basically the same tire, identical tread anyway) where mpg did not skip a beat.

 

Why I used that "nearly"
A more efficient tire could trump the old one, but we in NA do not have the means of knowing if a particular tire might do so before buying. Rolling resistance actually can be different between sizes of the same model tire, so reviews are hit or miss in terms helpfulness.

edit: changed "down" to the more sensible "do not"

 

Is it that the rolling resistance is more on a new tire or that the diameter is greater or both?

 

For sure diameter increase is a factor, but not that large. Maybe 2% at most?

 

I've heard the mold release compounds increase the rolling resistance of the top layer of rubber.

Whatever the exact cause, EPA rules for the MPG test disallow tires with more than 4000 miles of wear since the manufacturer is using worn tires on the test. So somewhere in between 0 to 4000 miles, the tires become 'broken in' for better fuel economy.

 

The deeper the tread, the more rubber is getting squished when it rolls into and out of contact. Since elastomeres lose energy when they compress and rebound, more tread means more rolling resistance.

Tires with 2/32nds left are great for mileage, but lousy in the rain.

 

I have Michelin Premier A/S on my PIP. Awesome in rain but a noticeable hit to MPG over the Energy Savers.

Will probably go back to the Energy Savers next time.

 

Yes, agree completely with this.

Less hysteresis loss... (I like fancy words..)