Does low rolling resistance == low traction?

[LordJim]

Saw a sign the other day for some new tires that made all sorts of claims about low rolling resistance. I couldn't help but think that low RR had to somehow translate into low traction. Am I wrong? What don't I get here?

 

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Jim

[whitetiger]

well, it depends on where you want traction. tires with the least RR will be tires with no tread at all such as race tires, which have the best traction on dry tarmac. However, race tires are crap in any other condition which is why tire makes put tread block on tires. A hich performace summer street tire will have only enough tread blocks to channel water away to prevent hydroplaning yet still remain superior on dry tarmac and they maintain a low RR.

 

at the other end of the spectrum are off roar tires which have a high RR but have great traction in snow and non paved surfaces.

 

For traction, its all about maximizing footprint and road surface contact. For RR, its all about tire smoothness. So a race tire will always have the least RR, but it will only have the best traction on try tarmac. Eveything else varys in the middle.

[TravisS]

There's a pretty good chance that too achieve that low rolling resistance the tire is going to have very hard rubber. This will most likely lead to extended life of the tire as well.

 

But, at least in the case where hard rubber is used, yes the traction will suffer.

[LordJim]

well, it depends on where you want traction. tires with the least RR will be tires with no tread at all such as race tires, which have the best traction on dry tarmac. However, race tires are crap in any other condition which is why tire makes put tread block on tires. A hich performace summer street tire will have only enough tread blocks to channel water away to prevent hydroplaning yet still remain superior on dry tarmac and they maintain a low RR.

 

at the other end of the spectrum are off roar tires which have a high RR but have great traction in snow and non paved surfaces.

 

For traction, its all about maximizing footprint and road surface contact. For RR, its all about tire smoothness. So a race tire will always have the least RR, but it will only have the best traction on try tarmac. Eveything else varys in the middle.

 

Interesting. I would have imagined that RR was a function of rubber on the road. Obviously a race tire should have more rubber on the road than a snow tire or well, pretty much any tire. Guess I need to think about this one a bit more.

 

Thanks for the info.

 

-

Jim

[LordJim]

But, at least in the case where hard rubber is used, yes the traction will suffer.

 

 

And that's what I was thinking.

 

-

Jim

[jbm]

It also has to do with how well the radius is maintained. Having to lift the weight of the vehicle when the radius is increased will result in higher rolling resistance. That's why a perfectly smooth round tire will have the least rolling resistance. That's also why a harder rubber will have a lower rolling resistance as it deforms less when it meets the road. If you think of a perfect circle meeting a flat plane (the road), it will have an infinitesimally small contact patch. As the tire deforms to the shape of the road, force is required to cause the deformation. This force causes an equal and opposite force against the direction of rotation which is what we call rolling resistance.

 

So the size of the contact patch isn't really the variable, it's the deformation of the tire which of course is related to the size of the contact patch.

[Montana]

Traction is also a function that varies at braking vs at take off vs when cornering, as it's part of the physics of motion. Another consideration comes from "sprung weight" and "unsprung weight" since sprung weight is distributed but unsprung weight isn't going to shift around, for example, the weight of your wheels and tires. That isn't distributed the way the body weight is distributed, say, upon braking, when available traction in front increases and the rear lightens. Unsprung weight is a drag.