Reducing rolling resistance?

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May 19, 2010 | 12:38 PM

#21

ZDan

Joined: Feb 2007

Posts: 6,863

Likes: 125

From: Pawtucket, RI

Quote:

Originally Posted by sahtt,May 19 2010, 11:43 AM

You can't simply "turn on" the tire surface's ability to stick to the road only when you need it.

Actually, high-performance track-worthy tires do need to get some heat into them before they "turn on". Particularly R-compounds. Grip is very noticeably reduced until they get up to temp. And they'll *never* get up to temp being driven normally on the street.

Quote:

It's based on the same principle as trying to roll a tire with sticky material on it versus a tire that doesn't, although much less obvious in nature of course.

Outright "stickiness" of even the highest performance tires, including R-comps, is often tremendously overstated. In my experience, yeah the get very soft and gummy, but as far as actual ADHESIVE stickiness (i.e., tractive GRIP even with zero normal force), there really isn't much.

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Your experience is meaningless,

Not to me it isn't! Perhaps you meant to say my experience is anecdotal, as is yours...

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but that's good you haven't noticed decreased mileage; wish I could say the same.

I'll fully agree that max and extreme performance tires may not be as optimized for low rolling resistance as other tires, but there's no reason they should be particularly bad. The adhesion/stickiness factor is a non-player.

BTW, early hybrid cars had special low-rolling resistance tires with tread compounds significantly SOFTER than normal high-mileage passenger car tires. UTQGs in the 100s and 200s. It was a major gripe for some, the tires didn't last nearly as long as most "normal" car drivers are used to.

May 19, 2010 | 01:18 PM

#22

ZDan

Joined: Feb 2007

Posts: 6,863

Likes: 125

From: Pawtucket, RI

Interesting link related to this discussion (including molecular bonding!):
http://www.school-for-champions.com/scienc...ion_rolling.htm

Excerpted summary:

Quote:

Rolling friction is the force that slows down the motion of a rolling wheel. This frictional force is typically a combination of several friction forces at the point of contact with the ground.

When the materials are both hard, static friction and molecular friction slow down the rolling. When the wheel or tire is soft, its distortion slows down the motion. When the other surface is soft, the plowing effect is a major force in slowing the motion.

Another link: http://www.tyres-online.co.uk/technology/silica.asp