Skinny vs. Fat....

[Zvoiture]

What gives you more dry grip, narrow tires or wide tires? Why is it universally accepted that wide is best? Does temperature of patch area figure in at higher psi's? (and I don't mean the pressure IN the tire). Lets ignore downforce in this discussion.

steve77

[jcdozier]

STEVE:

I'm not a tire expert, but I have a theory. If one makes the assumptions that two tires, one with 6-inch tread width and one with an 8-inch tread width are "equal" in all other respects, and that the fore-aft measurement of the "footprint" is, say 5 inches for both, the the "footprint" area of the 6-inch tire is 30 square inches and the area of the wide tire is 40 square inches. If one further assumes "grip" roughly equates to "friction", then 40 square inches will provide more "friction surface area" than 30 square inches. Good for dry, okay for damp, bad for standing water...

OBTW, I like your picture. Is that you on the right or the left??

[WishN4DaZ]

"Wider Is Better"

"Where the rubber meets the road"

Wider tires mean more grip, plain and simple, however! if your car doesn't generate a whole ish load of Ponies and torque...

you wont be able to turn those big ole tires over...which will bring you to a lower time...

Matt

[Phacade]

Having talked to a number of quote 'experts' on this matter, I have come to believe that the middle of the road is the best place to be. Obviously if your tires are too narrow then you get no traction, if they are too wide you feel every bump in the road. If you have traction and traction and handling is what you are after then wider is better. However, for the most of us, a nice 205 width to maybe 225 is acceptable. If you don't mind the bumps, and you want more traction and your getting some, then bigger is better.

EDIT: Maybe that last line didn't have the meaning I wanted it to have. I meant if your getting traction, then bigger is better; not if your getting some then bigger is....oh never mind.

[Zvoiture]

OK, but Timberwolf's theoretical two samples would provide: the wider, 40sq.in. footprint would have only 16 psi (2500lb car) while the narrower tires would have 21 psi on the road. It seems to me more psi pushing on the pavement would provide more grip. I know there has to be a 'happy medium'.

I just wondered--since everything else imaginable has been engineered to within an inch of its life--if there is a graph or sliding scale or formula or something where the 'best of both worlds' could be located.

steve77

[ZmeFly]

i can see that your thinking entirely to much on this subject. point is if you want more traction wider is better. but not for the fact of wet weather handling.

[Mike]

One thing we are forgetting here is usability. What's the purpose of the tire? Tires can be use for so many things, it's almost impossible to claim that wider is better.

If you're going to do off road rally... would you choose a wide low profile tire? Nope, you'd probably go with a tire designed for off road use which is taller.

Gonna do some road rally on pavement? Well, you probably want a wide tire and low profile so the tire doesn't lean around those corners or drift from side to side.

How about oval track? I don't know much about this one, but, I would think you should use a tire designed for high speed and longectivity (sp).

If the car is a daily driver, you probably don't want to go with low profile tires and big rims because it would be uncomfortable to drive. Yes, it might look good, but, if you drive an hour to work and another hour back every day... it can really wear you out. So, something around the 15" or 14" rim with a 60 series tire is applicable. And, do you need wide for this commuter? No. In fact, wide tires might be worse if you drive in a rainy climate such as up here in Oregon. Hitting a high water area on the highway at 60mph isn't fun... I couldn't imaging how the car would hydroplane if you had a wide racing tire on the vehicle.

So, there you have it. Determine the use and then go for the right tire.

[EScanlon]

One other item to consider here: Coefficient of Friction. i.e. that amount of force that can be exerted and still benefit from the counter force developed by friction.

Acceleration can only happen or push on the tires until the coefficient of friction is overcome, at that point you have a "burn out". Simple right?

Braking is the same, same with cornering.

Now, the discussion regarding the foot print:

A larger area footprint means the load (weight of the car) is exerted in such a manner as to be LESS weight per square inch of area. And that difference is what allows more force to be exerted both under acceleration and deceleration as well as lateral forces (cornering). So don't be fooled by the weight/area relationship you've established.

Mike has explained the major considerations to make, all else is just hype.

[XYZ]

ZV-

Check this book out some time and you'll probably get more info and theories than you care too but a really good reference. The book is called "How to make your car handle" written by Fred Puhn ISBN #0-912656-46-8. It covers all aspects of handling; suspension, tires, springs and struts, basic dynamics of cars and capabilities in turning etc. If you still have some questions then I don't know what to tell ya. It's a pretty interesting book. I believe that your analysis is on the right track about less weight distribution over a larger area but I also think there is some factor in there for slip angles, friction coefficient, handling characteristics, tire height, CG of car weight dist. etc.

I'm actually looking at a small section on the relationship of grip to weight. The last sentence says, "The rule is, when a tire is more heavily loaded, grip of that tire is reduced." Has to do with the vector forces of slip angle on the tire. I bet this book has the answer for you.

[MDyer]

I'm certainly no expert, but I've asked some folks w/ a lot more expertise than me, and they lean toward wider is better when considering all around performance. Ever seen an Indy, F1, or NASCAR on VW bug tires?