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Discussion Starter · #1 ·
I'm needing some help here,,,,I got into a discussion at work over the physics of tires. If I'm not mistaken, I once read that while driving down the road the contact patch that has contact to the ground is technically not moving. But once it loses grip, your tire will begin to do a burnout.

Am I right or wrong here? And if I'm right, does anyone know where I can find some information in this matter.

Thanks in advance.
 
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Discussion Starter · #2 ·
Re: Different type of tire question (blkhalo996)

if you're accelerating in a straight line, and you lose traction, (acceleration force greater than the coefficient of friction to maintain traction) the tire can/will spin. if it spins fast enough, the surface rubber can overheat and smoke.

the contact patch remains the same, but can fluctuate with weight, bumps and/or road surface. the "patch" is whatever section of the tire is in rotational contact with the road at the time.

is this what you're getting at?
 
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Discussion Starter · #3 ·
Re: Different type of tire question (Rigor)

Well, I was thinking more along the lines of a tank track. The part of the track that is on the ground is stationary and the tank then rolls over the track. I would think that the same principal would be the same for a tire, since the contact patch on a bike or car tire is flat with the ground. Also, like in funny-car pics, where the rim is actually twising in the tire. Most of the rubber is crunched up at the forward part of the rear tire.
 
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Discussion Starter · #4 ·
Re: Different type of tire question (blkhalo996)

That's pretty much it.

The tire tread/asphalt relationship is like a set of gears with really, really small teeth. If you could see the contact point through a microscope, you would see the rubber conforming to all the little cracks and crevices in the pavement. When the tire starts to spin, it's like grinding those gears...

So at the bottom point of each rotation, a given point on the tire comes to a complete stop for a very brief moment, unless it's spinning.
 
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Discussion Starter · #5 ·
Re: Different type of tire question (AZ Scott)

Unless you're corning, braking, or accelerating, then the tire's slipping.
 
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Discussion Starter · #6 ·
Re: Different type of tire question (Just Riding Along)

Yes, but slipping isn't the same as spinning.

Curious, blkhalo, what exactly is the debate here?
 
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Discussion Starter · #7 ·
Re: Different type of tire question (AZ Scott)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AZ Scott »</TD></TR><TR><TD CLASS="quote">Yes, but slipping isn't the same as spinning.

Curious, blkhalo, what exactly is the debate here?</TD></TR></TABLE>

I just asked if they believed that while driving down the road, is there any part of the tire static or not moving on the ground? Their thinking was that if any part wasn't moving the tire would rip. I remember reading it somewhere,,,,I want to say I read it in one of the Keith Codes "Twist of the Wrist" books, volume 1 I think.
 
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Discussion Starter · #8 ·
Re: Different type of tire question (blkhalo996)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blkhalo996 »</TD></TR><TR><TD CLASS="quote">Their thinking was that if any part wasn't moving the tire would rip...</TD></TR></TABLE>

They're high.
 
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Discussion Starter · #9 ·
Re: Different type of tire question (AZ Scott)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AZ Scott »</TD></TR><TR><TD CLASS="quote">They're high.
</TD></TR></TABLE>

and it's not green
 
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Discussion Starter · #10 ·
Re: Different type of tire question (AZ Scott)

The gear analogy is good for straight-line riding, but as I understand it while cornering the tire will generally be slipping somewhat unless the turn radius happens to match the camber-thrust cone radius - otherwise the tire's "gears" are grinding against the road surface (which is what shreds a tire). A good article explaining some of this is here (there's more in his book):

http://www.tonyfoale.com/Articles/Tyres/TYRES.htm
 
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Discussion Starter · #11 ·
Re: Different type of tire question (JeffKoch)

Straight line there's slip since the contact area's deforming constantly. That's the feel or feedback everyone talks about. If you're talking micro second measurements then after some steady state travel in a straight line the slip would vanish, and the tire would give you that tooth and cog analogy. That could be one of those "scientific" measurements that only exists in math since the tire's also a spring, and would still absorb input from the road.

There's an expanded explanation of this in Tony's book that I have not cut and pasted here. If you have access to the book or CD it's on page 2-16.

Halo, if you're talking to a room full of engineers, physicists, or other propeller heads they'd love the Tony Foale book.
 
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