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Old 03-23-2018, 08:06 AM   #41 (permalink)
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Quote:
Originally Posted by gumby79 View Post
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Tire slip is quantified by a formula known as the "Pacejka magic formula" developed primarily by the Dutch university professor Hans Pacejka. A curious aspect of this extremely complex subject is that some tire "slip" ( not sliding or wheelspin) is necessary for a tire to generate traction, and that there is an optimum amount of tire slip. This does not imply that wheelspin or skidding is desirable in land speed racing or in drag racing. .paterstreamliner.com/
As the tire wore out the volume of slip went down ?
Ah ..... Mmmmm ......

The Pacejka Magic Formula relates slip angle to cornering force generation. The website you quoted from is trying to relate Pacejka's "Magic Formula" to tire slippage in the tangential direction and that formula is not applicable. I'm not sure why they even brought the subject up as even their own words say there is some confusion about the terms used - and then they confuse the terms themselves!

And it certainly isn't applicable to the discussion above.

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Old 05-28-2018, 07:26 PM   #42 (permalink)
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https://www.truckinginfo.com/149929/mismatched-duals

I plan to setup a small experiment soon. The two rear tires on my car are about 2-3 32nds apart.
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Old 05-29-2018, 12:37 AM   #43 (permalink)
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the distance between the center of the wheel and the top of the pavement
is your effective radius
geometry will not allow for anything else
without spinning the tire on the rim

part of the tire is however behaving as pavement and causing some confusion

so to clear it up the flex point of the sidewall the invisible point inside the tread that acts as the hinge that point is the difference between the wheel and and the " tank tread "

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Old 05-29-2018, 08:36 AM   #44 (permalink)
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Quote:
Originally Posted by ASV View Post
the distance between the center of the wheel and the top of the pavement
is your effective radius
geometry will not allow for anything else
without spinning the tire on the rim

part of the tire is however behaving as pavement and causing some confusion

so to clear it up the flex point of the sidewall the invisible point inside the tread that acts as the hinge that point is the difference between the wheel and and the " tank tread "
I am not sure where this post fits in the scheme of things - BUT -

a) There is nothing you can measure in a loaded tire that will give you the effective rolling diameter (or radius).

b) There isn't a *point* where the tire flexes. The entire tire flexes, and it is most noticeable in the sidewall because it bulges out, but not at a single point. You could look at the sidewall as a arched leaf spring, where the end points are fixed, but compressed closer together. The entire spring flexes, but in the case of a tire, the area near the wheel is much, much stiffer than the rest of the sidewall.
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Old 05-29-2018, 10:09 AM   #45 (permalink)
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I have another thought that is directly related. Most low r tires also have lower tread depth than "normal" tires to reduce the tread deformation and thus wasted energy.

What if some of the gain in fe is from relatively more miles reported per mile?
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Old 05-29-2018, 10:52 AM   #46 (permalink)
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Thread depth does not influence rolling distance.
In the contact patch the thread lies flat on the tarmac, so a worn tire has the same rolling distance as a new one.

I tested and found the rolling distance of a fairly worn tire to be about 3 cm less than the circumference as measured over the thread. With new tires the difference should even be greater.
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Old 05-29-2018, 12:21 PM   #47 (permalink)
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Quote:
Originally Posted by CapriRacer View Post
I am not sure where this post fits in the scheme of things - BUT -

a) There is nothing you can measure in a loaded tire that will give you the effective rolling diameter (or radius).

b) There isn't a *point* where the tire flexes. The entire tire flexes, and it is most noticeable in the sidewall because it bulges out, but not at a single point. You could look at the sidewall as a arched leaf spring, where the end points are fixed, but compressed closer together. The entire spring flexes, but in the case of a tire, the area near the wheel is much, much stiffer than the rest of the sidewall.
you have seen a leaf spring?
the loop at the end is in fact a hinge
the junction between the sidewall and the tread
is the same

in fact the tires of the moon buggy work exactly like that
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Old 06-06-2018, 07:40 AM   #48 (permalink)
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This is the same dilemma as:
Does a lady walk faster when wearing high heels?

If you think about it, it al depends on the location of the ankle. From that point downward everything is always down and does not extend further to increase stride length. Even if you are wearing massive platform ahoes.
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Old 06-06-2018, 11:30 AM   #49 (permalink)
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Of course does a lady walk faster on high heels. I'm hopeless on them.
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Last edited by RedDevil; 06-06-2018 at 01:33 PM..
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Old 07-04-2018, 10:23 PM   #50 (permalink)
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Had the Energy Saver A/S on My Prius and I'm very pleased with them. These michelin tires are pricey but have great traction and very quiet on pavement.

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