I've wondered this for a few years now and finally decided to ask - why are wider tires supposed to provide better traction?

I remember learning way back when I took physics that traction depends on two factors - the weight exerted on a contact patch and the area of the contact patch. The equation for traction is one of those inverse relationships. For example;

(A)(b) = (a)(B)

So the wider tire has a bigger contact patch but less weight on each square inch of contact patch. So theoretically, a car with a 3" wide tire will get the same traction as a car with a 10" wide tire.

Who can school me?

 

No.. you got it. It's explained in detail on the D Series website.

 

I did some searches and couldn't find what you are referring to. You meant on d-series.org right?


Anyway, so what is the advantage (other than handling) of a wider tire?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">I remember learning way back when I took physics that traction depends on two factors - the weight exerted on a contact patch and the area of the contact patch. The equation for traction is one of those inverse relationships. For example;

(A)(b) = (a)(B)

So the wider tire has a bigger contact patch but less weight on each square inch of contact patch. So theoretically, a car with a 3" wide tire will get the same traction as a car with a 10" wide tire.

Who can school me?</TD></TR></TABLE>

Actually, the relationship typically seen in an elementary physics class does not even include contact area. Traction is considered to be equal to the product of the coefficient of friction (which depends on the two materials in contact) and the normal force. But as any physics book that gives this relationship should state, this equation is a gross oversimplification. One way of looking at things is that the coefficient of friction is not a constant. It does depend on the force per unit area. Specifically, the coefficient of friction seems to decrease as the normal force increases. So having a larger contact area is beneficial since it decreases the per unit area force, thus increasing the effective coefficient of friction.

 

sounds like you got schooled -

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">Anyway, so what is the advantage (other than handling) of a wider tire?</TD></TR></TABLE>


Um.......isn't that kinda the point?

Why is wider better? Let's see if I can do this so that it makes sense....

The "traction" of a tire is often confused as a product of the vehicle weight and the surface area in contact. Well, that's exactly backwards. The vehicle doesn't affect the traction of the tire - the tire affects the traction of the vehicle.

confused yet?

The traction of a tire is actually the static force (static friction) between the tire and the road. Ever notice it's harder to do a burn out after you've been driving for a while? That's because your tires have heated up and are "sticky", thereby requiring more power from the engine to overcome the static friction between the tires and the road, as opposed to when they are cool. Taking this into consideration, would you rather have 6" wide of sticky under you or 8" wide of sticky?

So to be totally correct, is should be said that wider tires increase the amount of force required to break the negative friction force (i.e. "sticky") between the tires and the road.

Notice that didn't mention one thing about the vehicle's weight? In most driving cases, the vehicle's weight actually is part of the force acting against the tires (other than the normal force required to hold the tires to the ground). Consider turning: Put a ball on the backseat. Take a left turn, what happens to the ball? It rolls to the right. The tangential force (remember physics?) acting on the ball overcame the static friction of the surface of the ball and the seat, thereby pulling it in the direction of the force. Put some duct tape on the ball and try that turn again - it takes a lot more force to move it, if it does at all.

I guess I should rap this up.....the traction of a tire is dependant on the friction between it and the road. The more material you have in contact with the road increases the amount of force required to break that contact. Making that surface hot (rubber + hot = sticky) increases that friction exponentially.

Sorry so long-winded....hope it helps.

 

Wait, are we talking about drag racing or road racing? In road racing, you reach a point where wider tires does nothing for you. On our cars, this is between 195 and 215 width tire as in 205/50/15 or so. You can get the details and even physics (if you're a sick bastard for that kind of thing) from various books on racing (do a search) like the Handling Handbook by Don Alexander.

For drag racing, I think you use the minimum tire that you need, or the widest tire that is practical. Wider is probably always better if you have the power for it. Drag racing is not my interest though.

 

Actually from a drag racing stadpoint wider is not necessarily better for traction. Taller is better for traction. With a taller slick there is much more rollout that the tranny must turn to move the car. This is why we see many people breaking more tranny's with 26" and 28" than with 24.5" and below. Since drag racing is pure acceleration the more contact patch you have with the track the better times will be (as long as you have enough power to turn the slick). If you guys have anymore input please add as this is a very interesting post.

 

I get it.

Tires are not made wider for better traction. The fact that they are wider is a result of the soft compound - they have to be wider in order for the soft sidewalls to support the vehicles weight. A skinny slick would provide the same traction but it's unsafe to have 2000lbs pushing down on a skinny slick.


So getting wider tires (for drag racing) has nothing to do with contact patch. A 4" tire and an 8" tire both made out of a harder compound will both get the same traction.


Also, it's better to have a wider tire because it keeps the car going straighter down the track and helps prevent rollovers. They also last longer.


5mins on teh google

 

Alrighty!
f=uN
friction= coefficient of friction times the Normal (weight or mass times gravity)

The coefficient of friction is the contact between the tire and road, which both can be different composites which result in different coefficients. In theory, the tire is round and only comes into contact with the road in one spot. That is why Hoosiers can turn a car, they stick to the ground as opposed to retread tires, which suck ***.

Yes, the heavier the car, the harder it is for it to skid (the transfer from static friction to the other friction...forgot sorry!) Once you skid, the friction changes and that's why it is easy to keep skidding (drifting)

The wider the tire comes with torque (equal Force time distance from pivot point)
Look at the BMW M3. Wide tires because of huge torque out the rear. If you derive this equation torque depends on surface area. The bigger the surface area the more torque transferred to the ground.

I was majoring in physics for a while then decided to become a chemist.

 

F(traction) = mu * F(normal)

That's the equation you get in basic physics. What they don't say in high-school is that the coefficient of friction (mu) is not even close to being constant.

Notice there's no contact area; it drops out of that equation. But in real life the value of mu depends on the area & pressure. (And temperature, rubber composition, etc...)

But the car's 'handling' depends on how the tire behaves BEFORE it lets go of the road. A skinny tire has a contact patch that's long & narrow. A wide tire has a contact patch that's short & wide. For the same air pressure & same vehicle weight, the area is the same, just the shape is different. But it makes a difference in how it behaves. Taller or shorter sidewalls behave differently, even for the same width of tire.

So you got all this other stuff that's not really based on that equation up there. Tires' slip angle as it rolls down the road, & how much that slip angle changes with different loads, is what make all the difference.

 

you're confusing the terms traction and pressure. weight / area = PRESSURE not TRACTION...traction has more to do with the interface between two surfaces right? not just the physical contact patch.