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      06-28-2011, 06:43 PM   #1
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Physics ITT

So, long story short, taking a physics class at a local CC and learning about friction, yada yada. Prof asked the class why racecars have wide tires, and I'm not a physics major so I was stumped with the rest of 'em.

So, why do racecars have wide tires? Considering friction is independent of surface area, it throws out any theories I have...
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      06-28-2011, 06:49 PM   #2
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Because Race Car
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      06-28-2011, 06:51 PM   #3
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wider tires have better lateral traction and have better heat management properties than narrow tires
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      06-28-2011, 06:51 PM   #4
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wider tires make stuff go faster. duh
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      06-28-2011, 06:59 PM   #5
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Quote:
Originally Posted by TiAg335i View Post
wider tires have better lateral traction and have better heat management properties than narrow tires
'scoose my ignorance, but what IS lateral traction?
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      06-28-2011, 07:00 PM   #6
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Is friction really independent of surface area? The coefficient of friction is independent, but the overall magnitude of friction might be affected by the surface area in contact with the road and the weight of the car.
Hmm good question though, and good topic lol
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      06-28-2011, 07:01 PM   #7
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lateral grip is how much grip the tire has when going around a turn. You might recognize the term Lateral G's from car mags. Tires have much to do with this figure.
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      06-28-2011, 07:03 PM   #8
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Quote:
Originally Posted by eVitO View Post
'scoose my ignorance, but what IS lateral traction?
When your making a turn a wider tire will have more surface area contacting the road than a narrow tire.
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      06-28-2011, 07:03 PM   #9
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Well, considering this was a high school with ash-trays, I'd imagine your professor wanted you to ask a BMW forum for an insightful answer... or google.com.
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      06-28-2011, 07:06 PM   #10
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Quote:
Originally Posted by TimZ View Post
Is friction really independent of surface area? The coefficient of friction is independent, but the overall magnitude of friction might be affected by the surface area in contact with the road and the weight of the car.
Hmm good question though, and good topic lol
That's what I thought... f=m*g*(mu) proved me wrong and I was like durr.
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      06-28-2011, 07:08 PM   #11
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Quote:
Originally Posted by SchlauCow View Post
Well, considering this was a high school with ash-trays, I'd imagine your professor wanted you to ask a BMW forum for an insightful answer... or google.com.
It's extra credit, but considering google has more worthless answers than religion (sorry if I offended anyone), I thought I'd ask people who are even slightly interested in this topic as well.
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      06-28-2011, 07:09 PM   #12
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Quote:
Originally Posted by ErvGotti View Post
When your making a turn a wider tire will have more surface area contacting the road than a narrow tire.
But again, surface area is independent of friction, so I still don't understand where this puts me at...
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      06-28-2011, 07:14 PM   #13
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it's kind of a loaded question. There are so many things that go in to getting grip from a tire. Width is part of the equation but the most true answer would be: Because the sanctioning body for the racing series dictates what size tires they use; they are usually wide.


Non fancy physics answer:
Tires can only do 3 things for a car. Make it go forward, stop the car and turn the car. Tires have X quantity for maximum grip. So that tire can only administer that much grip for one of those tasks. If you ask it to make the car go forward while turning, X quantity of max grip is split up between those two tasks. ie, 40% for lateral grip with 60% forward grip may be needed just after the apex of a turn. So one way to make that 40% and 60% equal more grip is to widen the tire. Others would be stiffen or soften the sidewall or make the rubber compound softer. There is a limit to the benefits of width though.
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      06-28-2011, 07:23 PM   #14
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Quote:
Originally Posted by eVitO View Post
It's extra credit, but considering google has more worthless answers than religion (sorry if I offended anyone), I thought I'd ask people who are even slightly interested in this topic as well.

I commend you on your troll avoidance skills
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      06-28-2011, 07:24 PM   #15
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Quote:
Originally Posted by SchlauCow View Post
I commend you on your troll avoidance skills
I figured NO ONE would help me if they just got angry at me.
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      06-28-2011, 07:31 PM   #16
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Quote:
Originally Posted by MP0WER View Post
it's kind of a loaded question. There are so many things that go in to getting grip from a tire. Width is part of the equation but the most true answer would be: Because the sanctioning body for the racing series dictates what size tires they use; they are usually wide.


Non fancy physics answer:
Tires can only do 3 things for a car. Make it go forward, stop the car and turn the car. Tires have X quantity for maximum grip. So that tire can only administer that much grip for one of those tasks. If you ask it to make the car go forward while turning, X quantity of max grip is split up between those two tasks. ie, 40% for lateral grip with 60% forward grip may be needed just after the apex of a turn. So one way to make that 40% and 60% equal more grip is to widen the tire. Others would be stiffen or soften the sidewall or make the rubber compound softer. There is a limit to the benefits of width though.
Anyway you can give me the fancy physics answer?
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      06-28-2011, 07:39 PM   #17
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      06-28-2011, 07:39 PM   #18
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math sucks.

Wide tires work better because they provide more surface area contact with pavement.
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      06-28-2011, 07:53 PM   #19
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Wider tires look cool.
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      06-28-2011, 08:11 PM   #20
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      06-28-2011, 08:41 PM   #21
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The simple answer lies with wear and materials strength, not friction. Race cars have softer tires and thus wear faster (given all the lateral Gs). Unless you want to be changing tires every lap, you use wider tires.

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      06-28-2011, 08:48 PM   #22
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Quote:
Originally Posted by schoy View Post
The simple answer lies with wear and materials strength, not friction. Race cars have softer tires and thus wear faster (given all the lateral Gs). Unless you want to be changing tires every lap, you use wider tires.

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Quote:
It's because real friction forces, unlike the ones they teach you about in physics class, do depend on contact area.
http://www.physicsforums.com/archive...p/t-56486.html
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