Different Tyres Affect Fuel Consumption?

colin79666

mikey72 wrote: »

How does rollig resistance, (which is mainly deformation of the sidewalls) help you stop?

It has everything to do with helping you stop. More resistance (friction between the road and tyre) = more grip.

Tyre manufactures have done wonders with some tyres, reducing resistance when you want to go but using clever tread designs to keep grip when the brakes are applied.

mikey72

colin79666 wrote: »

It has everything to do with helping you stop. More resistance (friction between the road and tyre) = more grip.

Tyre manufactures have done wonders with some tyres, reducing resistance when you want to go but using clever tread designs to keep grip when the brakes are applied.

That's a common misconception of what rolling resistance is.

As you roll a tyre, the tyre deforms, so you have to roll it over the flat spot at the bottom, and push the sidewalls out of shape.
An eco tyre has firmer sidewalls, so the deformation is less, hence less resistance to rolling. (Why a highly inflated, stiff tyre is easy to roll, a flat tyre is harder).

Grip is (mainly) to do with friction between the tyre and the road, and more influenced by the tread, and rubber compound.
Admittedly, if it was super sticky, the act of peeling it from the road would increase rolling resistence, but usually it mainly affects the shear.

If you drive with a normal tyre, and overinflate it, you'll get more mpg. If you underinflate it, you get less.
In this case grip will normally change, usually both for the worse, as you're now using the tyre at the wrong pressure though.