Tyre grip VS tire rolling resistance

[xpensive]

...
But no, this has nothing to do with heating up tires or anything temperature related. Traction effectively comes directly from energy loss. Better read up on that *.pdf, bud!

Afraid I'm at a loss here. If traction "effectively comes directly from energy-loss" as you say, but without "heating up tyres",
what's the function of said loss and what happens to that energy anyway? A three-line crash-course perhaps?

[Jersey Tom]

Afraid I'm at a loss here. If traction "effectively comes directly from energy-loss" as you say, but without "heating up tyres", what's the function of said loss and what happens to that energy anyway? A three-line crash-course perhaps?

You can't be at too much of a loss as you're speaking to this already in another thread:

But on typical tarmac, the rubber will follow the irregularites of the surface, thus creating direct horizontal forces...

All the asperities or texture on tarmac giving rise to high frequency excitation of the tread are generating forces via the hysteretic component of tire traction (as opposed to adhesive or more traditional "smooth" coulomb friction). Hysteresis = energy loss.

[thisisatest]

i'm sure there are some large, fundamental differences between a car tire and a bicycle tire, but i thought i'd add this little bit:
with bicycle tires, a large contributor to rolling resistance is the casing material and construction method. typical racing bike tires start with a casing material that has 120 threads per inch, usually of nylon, two layers on the sidewalls overlapping to three layers over the tread. other tires, mostly made by Vittoria, use a poly/cotton blend for the casing, with much finer fibers at up to 320 tpi. the casing becomes thinner and there is essentially less rubber in there. some track and record-attempt tires have silk casings. generally, the more supple the casing material, the lower the rolling resistance, AND the better the traction, all else being equal.

[ubrben]

...
But no, this has nothing to do with heating up tires or anything temperature related. Traction effectively comes directly from energy loss. Better read up on that *.pdf, bud!

Afraid I'm at a loss here. If traction "effectively comes directly from energy-loss" as you say, but without "heating up tyres",
what's the function of said loss and what happens to that energy anyway? A three-line crash-course perhaps?

Where do you think marbles come from? If you take an rubber eraser and rip it in half chances are it's warmer than before you started...

To be a little more helpful, there's two things going on. When you generate lateral force you have to have a slip angle (and therefore a sliding speed) force x speed is N x m/s i.e. work done per second aka power in watts. Integrate that w.r.t time and you have N.m i.e. work done aka energy.

In the case of "grip" that process is mainly going on on the surface of the tyre. If the rubber can't deal with that energy input if will break down, wear out, grain, or all manner of other things.

As all that's occurring on the tread surface the tyre is rolling. As a portion of the tyre enters the contact patch it will compress and then extend as it leaves the contact patch. This deformation tends to be in the upper sidewall and base of the tread (think cantilever beam - bending moment is highest at the base) due to visco-elastic properties of rubber this deformation causes energy to be dissipated resulting in heat buildup.

There is only so much you can do to decouple the two mechanisms (particularly what's occuring at the tread base) when the tread is a matter of mm thick.

Ben

[Jersey Tom]

I should clarify from before... highly hysteretic treads WILL run hot, but the difference in running temperature isn't necessarily what leads to improved ultimate traction.

Should also be noted that hot does not necessarily = good, and that some tires are less temperature sensitive than others.

[xpensive]

...
Where do you think marbles come from? If you take an rubber eraser and rip it in half chances are it's warmer than before you started...

Ben

Boy that's deep, but let's see, from the tyres perhaps, a heated up tyre that is?

As for erasers, I rarely use them so I wouldn't know, will I burn my fingers?

[volarchico]

As for erasers, I rarely use them so I wouldn't know, will I burn my fingers?

Yes. Avoid excessive eraser usage at all costs.

[Jersey Tom]

As for erasers, I rarely use them so I wouldn't know, will I burn my fingers?

Yes. Avoid excessive eraser usage at all costs.

Good advice. Excessive eraser usage generally goes along with f'ing something up big.

[xpensive]

...
To be a little more helpful, there's two things going on. When you generate lateral force you have to have a slip angle (and therefore a sliding speed) force x speed is N x m/s i.e. work done per second aka power in watts. Integrate that w.r.t time and you have N.m i.e. work done aka energy.
...
Ben

Point is that rolling resistance will come without "slip angle", actually without neither torque nor lateral force on the tyre,
even a free-rolling car will have rolling resistance from the hysteresis of he tyres alone.

Every kid with a 20" bike trying to compete downhill with his older brother's 28" knows that.

[DaveW]

Apologies for butting in on a good discussion, but

Every kid with a 20" bike trying to compete downhill with his older brother's 28"...

would be wise to read the whole of Ben's post. He might then, possibly, learn something ...

[xpensive]

...I believe you failed to finish that sentence Dave, what do you mean that Ben is supposed to learn?

[ubrben]

...
To be a little more helpful, there's two things going on. When you generate lateral force you have to have a slip angle (and therefore a sliding speed) force x speed is N x m/s i.e. work done per second aka power in watts. Integrate that w.r.t time and you have N.m i.e. work done aka energy.
...
Ben

Point is that rolling resistance will come without "slip angle", actually without neither torque nor lateral force on the tyre,
even a free-rolling car will have rolling resistance from the hysteresis of he tyres alone.

Every kid with a 20" bike trying to compete downhill with his older brother's 28" knows that.

I completely agree.

The point I was making was that you are limited in how much you can decouple grip and RR when both mechanisms (frictional sliding and viscous heating) are occurring at the same time in a corner and the tread has very high hysteresis and is only 3mm thick for example.

Ben

[ubrben]

...I believe you failed to finish that sentence Dave, what do you mean that Ben is supposed to learn?

I think he meant you might learn something. More's the point I think you know that's what he meant

Ben