Rolling Resistance vs. Temperature

[RedDevil]

So I just repeated the test with some rubber bands, but they remained flexible ???
Ahhh, not all rubber is the same. Need the black vulcanized stuff that is not too flexible at room temperature, I guess.

[oil pan 4]

You might be able to increase tire temperatures slightly with an Argon fill.

Argon is used as thermal and sound insulation between the layers of glass in higher end windows.
In a tire it should help keep the heat in the tires tread, since Argon offers lower thermal conductivity than air.

An Argon tire fill wont elevate temperatures to an unsafe level since there is a least one OEM that I know of who fills tires with Argon from the factory.
Lexus Argon fills their tires from the factory to reduce road noise, to at least help get the car off dealers lot.

A standard argon welding bottle regulator puts out right about 50psi, enough pressure to fill any car tire, any load range C and most LT truck tires.

I plan to argon fill my trailer tires to finish off my argon bottle when it gets low, not to reduce RR but to help fend off dry rot from oxygen permentation.

[mort]

Originally Posted by Frank Lee

I disagree.

You say steel belts are the biggest contributor to r.r. when actually they are the biggest thing that reduces r.r.; steel springs back efficiently thus returning nearly all the energy it took to deform it vs rubber which due to hysteresis doesn't return as much when "undeforming"; thus the rubber is the culprit in absorbing energy when rolling.

This would be true if the steel belt was a band of sheet metal. But it a woven belt, and flexing causes some of the wires to slide across other wires. through the weave, for which there is no rebounding force. That is pure hysteresis. I stand by my statement.
But don't try to slide the context out from under me. I'm talking only about steel belted radials. In other tires there are other contributors to RR. In non-belted tires (bias ply) squirm is the overwhelming source of RR.
-mort

[Frank Lee]

http://deepblue.lib.umich.edu/bitstr...2B0?sequence=5

Here we are- an oldy but a goody. Don't worry; there's good stuff early on.

P.S. Here is a "little bit more"...

http://books.google.com/books?id=zcZ...stance&f=false

Pg 67 sez steel cords rule for fe.

[wdb]

I can add anecdotal information about viscosity and cold weather. When I start my Subie in the winter and let the clutch out (in neutral), the load it places on the engine is palpable; the revs drop, the computer compensates. The car even moves a bit, so I make sure the handbrake is set before letting the clutch out. For the sake of comparison on that engine (2.5L turbo flat four), when the AC comes on there is no discernable difference in load whatsoever; I just hear the clutch lock in.

That's just the oil in the transmission. No diffs are turning, no wheel bearings either.

[slowmover]

I'd alert professional tire engineer (and contributor) CapriRacer to this thread.
.

[Diesel_Dave]

Originally Posted by Frank Lee

http://deepblue.lib.umich.edu/bitstr...2B0?sequence=5

There's a plot on pg. 5 showing the exponential dependence of rubber loss characteristics to temperature.

[CapriRacer]

Originally Posted by slowmover

I'd alert professional tire engineer (and contributor) CapriRacer to this thread.
.

I seem to remember there's data in the NHTSA book on tires. I'm not near my copy at the moment so I'll post back when I've done the research.

But a couple of comments are in order:

Rubber hardly contributes at all to the stiffness of a tire. Stiffness is mostly inflation pressure related - at least as far as RR is concerned.

The steel belt isn't woven. It's 2 layers of parallel wires - one going one direction and one going the other. If you X-ray a tire, it may look like it is woven, but that's just an optical illusion.

Yes, a steel belt really changes the stiffness of a tire, but since we are talking passenger car tires where virtually every tire is a steel belted radial, the steel belt hardly makes any difference from tire to tire.

What really contributes to a tire's RR is the nature of the the tread compound. The technical term is hysteresis, and it is a measure of how much energy you put in to bend the compound, vs how much you get back out when you allow it to return to its original position. Even very stiff rubber compounds could consume more energy.

In fact, low RR tread compounds tend to be soft - just like grippy tread compounds. Long wearing compounds tend to be hard. So you can't tell if a tread compound is a LRR compound simply by measuring it's hardness.

So the rubber band experiment was not measuring the important property.

[RedDevil]

Bicycle tires have no steel belts and do have higher rolling resistance when cold.
So why would it not have that effect on car tires? As it seems to fit with the roll test observations?

I can add mine. Car tires cool off quicker than the engine and bearings. So leaving the car park in a workday evening after dinner in the cold, car still warm, sees bad free rolling in neutral, engine killed. Leaving in summer with a cold engine etc. got me rolling much further.
Same tires, 1985 Honda Civic, testing done in 2001, but no less true today.

[Frank Lee]

My first link graphs cool-down and it really cools a lot in the first 10 min.