Axle/bore friction

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joe
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Axle/bore friction

Post by joe »

If you choose wheels with smaller bores, let's say .094" as opposed to .095" (I don't recall the real numbers); is there a savings in overall friction, and if so is the corresponding reduction in friction linearly related to the bore size? i.e. the circumference of a .094" bore is about .295" and a .095" bore is about .298". The smaller bore presumably has 1% less braking torque (is that right?), is this a 1% savings in friction or is there some other more difficult way to figure it out? I already know that the smaller bore gives a little better "ride" so to speak because the wheel is a bit more stable.
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Re: Axle/bore friction

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Re: Axle/bore friction

Post by joe »

OK, I read that, it's interesting. It says (not related to above):
Car modifications that can reduce the CRF can reduce the rolling resistance by the same factor. For example, a "V" or "H" tread pattern limits the contact area between the wheel and track and thereby reduce the CRF and rolling resistance. Note that a raised wheel does not reduce the overall rolling resistance since the full weight of the car is distributed over the remaining three wheels and increases their rolling resistance. However, the rolling resistance is greater for the rear wheels in a rear biased car since they bear a greater fraction of the weight.
I don't understand why a V tread, which they say reduces the contact patch, lowers the rolling resistance, but using one less wheel, which by this same explanation you would think also reduces the contact area does not. The explanation is that the full weight of the car is distributed over the remaining 3 wheels. Yet the full weight of the car is still on the V tread also, and the pressure is greatly increased (intuitively although I'm not so sure if the wheel is mostly inflexible). There seems to be some disagreement about rolling resistance among physicists. One can find plenty of explanations on the web that INSIST that the rolling resistance is actually lowered by a shorter yet wider contact patch, when the tire pressure remains constant. They say the wider wheel would be more favorable because of the SHAPE of the contact patch.

I think these physicists would say that the V tread has a longer contact patch since the weight is being distributed over a smaller tire; and that the wider tire would thus have a much shorter yet wider patch. It is also OFTEN the flex in the tire sidewall that increases rolling resistance in pneumatic tires.
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