Quote:
Originally Posted by slowmover
I'd alert professional tire engineer (and contributor) CapriRacer to this thread.
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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.