Does added tire width actually increase contact patch?
I got into it recently with a bmw guy on this issue, and I'd like to know what the racers take on it is. And it's not nearly as simple as you might think. But before I post results I'd like to see what people think. All else the same (diameter of wheel and tire, PSI, Tire Compound, car weight)
Keep this in mind. Pascals principle...Archimedes may apply also... assume the car is supported by the air pressure, ie, ignore the sidewalls or assume they are the same for both tires, assume it's 50 psi inflation... each wheel supports 1000 lbs... what is the force on the ground? 1000 lbs. what is it's area? 1000 lbs / 50 lbs/in^2 = 20 in^2 (the lbs cancel) tire shape does not enter into it...it will take what ever shape the tire configuration will allow, but it will be 20 sq in, regardless... if the tire is very, very narrow it will be a 10 L x 2 W patch if the tire is very wide it will be a 2 L x 10 W patch it has to: it has to support the car...and the force on the ground has to equal the wt of the car and air presure (force) supporting it, exactly equal so they cancel, the definition of static system... |
The Mark Donohue principle still holds true is all I would say....
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a "wider tire" on a "wider wheel" answers your question.
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Well appearantly this has been a heated debate because accoring to physics, the contact patch should be the same, with the tire adjusting to the weight of the car, no matter what the size of the tires, at least that's what some people have been arguing, it makes sense to an extent though. A smaller tire gets compressed more, making it flatten out and put more % rubber on the ground and certain PSI than would that same weight on a wider tire.
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My 2 cents
A wider tire will have a larger contact patch if all other factors are equal (brand, model, air pressure, aspect ration, and if mounted on a rim of the correct width, etc. The weight distribution or lbs per sq. inch in the contact patch will decrease on the wider tire due to the wider contact patch. |
What if the tire were 100 yards wide? Would it have the same contact patch/area where the rubber meets the road as a tire that is only six inches wide, diameter of wheel and tire, PSI, tire compound and car weight all being the same?
I don't think so. |
A tire is clearly not the theoretically perfectly flexible bladder that elementary
physics requires for a car to be supported only by pressure. A tire is somewhere between the perfectly flexible balloon and a solid block. Elementary physics would say that a solid block's contact patch would grow linearly with an increase in block size. Particularly for current stiff-walled tires, the contact patch can be significantly the same in size for a range of pressures, and can certainly be bigger with a bigger tire. |
Given the usual "all other things being equal" part of this argument inducing question, which all other things never are, and given the restrictions of the possible tire sizes that any particular car can utilize, the reality is that the differences in contact patch are very small, if there is any. The important issues that come into play with different size tires are the differences in the shape of the contact patch, as well as those many variables that are existent with different tire sizes....sidewall height, etc.
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of course the contact patch gets larger for a wider tire/wheel. It's the pressure across the contact patch that decreases with a wider tire/rim since the weight of the vehicle is supported by a larger area you get a lower lbs/sqr inch.
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Originally Posted by Paul 996
(Post 4556771)
of course the contact patch gets larger for a wider tire/wheel. It's the pressure across the contact patch that decreases with a wider tire/rim since the weight of the vehicle is supported by a larger area you get a lower lbs/sqr inch.
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I would agree that the contact patch gets WIDER with a wider tire, but I'm not so sure the total area will be much different...
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I am no physicist, but this is a no brainer.....
otherwise one size would fit all....... |
Originally Posted by Mark in Baltimore
(Post 4556629)
What if the tire were 100 yards wide? Would it have the same contact patch/area where the rubber meets the road as a tire that is only six inches wide, diameter of wheel and tire, PSI, tire compound and car weight all being the same?
I don't think so. |
Geez, with a wider tire on a wider wheel, of course it's bigger. The real question is what about a wider tire on the same wheel? :corn:
Steve |
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