Fat rear tires

[Blair15951]

I was thinking about getting some more aggressive rims and tires.
Thought about going with some nice fat tires in the rear but physics tells us that friction is independent of surface area
friction depends on the weight of the car not surface area
so fat tires will be just as effective as skinny ones

however, supercars have really fat rear tires
so whats up?
someone needs to explain this to me bc i cant find anything on the internet

[redlude97]

You are oversimplifying the problem. You have to consider the change in the contact patch as the car moves dynamically. Read up on slip angles, then post back

[Blair15951]

im still not seeing how that has anything to do with the traction

it doesnt matter how much of the tire is in contact with the road
or what part of the tire is in contact with the road

its all about the weight pushing down that determines how much friction you get
and how much traction you get

maybe my logic isnt right?

[redlude97]

did you do ANY reading on the subject?

[Blair15951]

yes i did
but i dont think you know what youre talking about
because you cant seem to explain anything

[redlude97]

Then if I don't know what I'm talking about, please enlighten us on your vast knowledge on the subject. Once again, you are over simplifying the problem

[Sbeck]

Wider tires = more contact patch

more contact patch = more traction

Go ahead and make your car heavier.....we will all sit here laughing. It's not like the G35 is heavy enough...right

[Blair15951]

no thats not how friction works
friction is dependent on weight
not surface area

therefore

more contact does not equal more traction
thats why race cars have wings and not tires that run the full width of the car

im guessing that wide tires have some effect but no one can offer a logical explanation of why

[mr.stealth]

so why do fwd drag cars have huge drag slicks while at the same time keeping the car as light as possibly keep in mind weight is also transfered toward the rear during accleration.

[redlude97]

Conventional concepts about coefficient of friction are thrown out the window when you are considering materials that are not infinitely hard and abrade due to the friction between the surfaces

[CalsonicVQ]

Taken from post #6 in here: http://www.autocross.us/forums/index.php?showtopic=4410

For the same vertical load and internal pressure, a tire with a wider tread has a shorter, wider contact patch than a narrower tire. The area of both contact patches is the same if the internal pressure and the load are the same. . . A shorter contact patch at the same slip angle begins to slip at roughly the same distance from the leading edge as with a long contact patch. But the shorter contact patch has more of its length stuck to the road than the longer, narrower contact patch; and therefore a larger portion of its overall area is gripping.

And here's basically the same explantion but with some visual aids: http://stockcarscience.com/blog/inde...009/03/22/p108

[Alan]

Originally Posted by Blair15951

friction is dependent on weight

incorrect. its downward force. weight is one source of it because of gravity. look at an F1 car. very light, tons of downforce, tons of grip!

[Blair15951]

haha no
im not talking about the material

im talking about the width
say you have a G35 with super fat tires
and the same G35 with skinny tires (both made from the same material)

technically, according to the laws of physics, you will get exactly the same amount of friction
and therefore the same amount of traction

but supercars and race cars have fat tires
why?
i dont know maybe we'll never settle

[Blair15951]

ohhhhh
CalsonicVQ
youre right
thanks dude
i see now

everyone else read that
its all about the amount of time the tire is in contact with the road
wide tire=longer contact
=more traction

[redlude97]

Originally Posted by Blair15951

haha no
im not talking about the material

im talking about the width
say you have a G35 with super fat tires
and the same G35 with skinny tires (both made from the same material)

technically, according to the laws of physics, you will get exactly the same amount of friction
and therefore the same amount of traction

but supercars and race cars have fat tires
why?
i dont know maybe we'll never settle

For perfect surfaces interacting with no change in surface characteristics due to slip. Like I said, you are oversimplifying the problem