LAC: Biodiesels, Diesels, TDIs' etc...

[Mark R]

Actually, overall tire construction has a significant effect on MPG.  Rubber
compound, tread design, as well as construction.
In a nutshell:
Rubber compound- the softer the compound, the more the tread blocks can
squirm for grip.  Tread block size and design is how they help stop (or
create) major squirm from occurring.  Most Nokians you can flex with a bare
hand.  That motion consumes energy and increases rolling resistance.  You
don't slip, you handle better, but think of it this way- it takes energy to
squish the compound into the pavement, and takes energy to suck it off.  An
engineer might think in terms of coefficient of friction.

Tread design- overall wind resistance and amount of rubber in contact with
the road.  An engineer might think in terms along the lines of coefficient
of drag.

Construction- Those new tires with the layers of soft cushy materials to
smooth out the ride?  That adds weight and rolling resistance.

OK- REALLY in a nutshell:
Basically, a tire which is narrow, light weight, well designed tread for
airflow, and has a hard compound will provide the best gas mileage.

Yes, as a track dude and Tire Rack dealer... I NEVER purchase a tire based
on the above criteria.  I just wanted to chime on purely on MPG.

And if anyone tries to put wide, sticky tires on their Prius- you can all
stand next to me pointing and laughing at them.
(Then they can laugh at me when I drop $100.00 of gas into my Escalade EXT
on the way to NHIS in a few weeks).   =)

Oh, and light rims with little airflow helps, too.  Pie-plate style covers
from the 50's can work wonders.  Or even better--- fairings.

Cheers!
Mark Rosenkrantz

On 4/28/06, Ed Kellock <ekellock at gmail.com> wrote:
>
> Wouldn't the weight and the probably larger, wider size of the performance
> rubber be the real cause of the mileage difference and not the amount of
> grip the rubber has on the road?  Just doesn't seem like the grip could
> account for really any change in mpg.  Don't most poeple run smaller,
> narrower rubber in winter than in summer?  And in many cases, different
> wheels too?
>
> Ed
>