Do wider tires grip better - all else being equal?

[XH29N0G]

Do wider tires grip better for acceleration - all else being equal? 

I see all sorts of discussion on the internet that say there should be no difference.  I am wondering if this is correct.

[Ghoste]

It comes down to a few things ( sidewall stiffness, rubber compound etc.), but all things being equal the wider tire is putting a greater contact patch of rubber to the road surface so yes, it should grip better.

[Mike DC]

                   
When you say "all else being equal" do you mean the contact patch size?  As in, comparing a wider/lower tire to a taller/narrower tire with the same total area of contact patch?  

For acceleration, I don't know.  


But wider tires definitely grip better for cornering, at least in theory.  It's because the wheel on a cornering car has a curved path but the tires don't roll that way, so only a sliver in the middle of the contact patch (front to back) can be perfectly in line with the car's travel at any time.  (Same principle for why you need a differential of some kind allowing the inside & outside wheels to travel at different speeds.)

Like I said, this is the theory.  As a practical matter the suspension's alignment/geometry limitations usually cancel out the gains from this.  It's rare that the suspension holds a tire PERFECTLY perpendicular to the road while under cornering G-forces.  Even a solid rear axle ends up with the contact patch being slighting cambered because the tire itself flexes.  The wider the tire, the wider the contact patch, the more it magnifies the effects of imperfect camber.

[XH29N0G]

All else being equal, I meant aspect ratio, diameter, compound, tread, etc....

What I read is that a taller tire is supposed to make a difference, and a wider tire would do better on corners, but for straight line acceleration, having a wider tire means (1) the contact patch increases, but the weight/area on the contact patch decreases and this is supposed to cancel in the total force that can be applied to acceleration.  I have not yet seen discussion of whether this applies both to the case where the tire is not spinning and the case when the tire is spinning.  I have seen some discussion that the forces on a narrower and narrower tire, being distributed over a smaller amount of rubber, will ultimately cause a very narrow tire to fail.

I do not have a background in engineering or physics, so I cannot tell if there is anything wrong with what I have read, and if there are other real world considerations that make a wider tire better for straight line traction.

So that is what I was asking. 

Thanks for the responses so far.

[Cooter]

Depends on the suspension. I've seen big tire cars that didn't hook as well as one with a 9" tire.

[twodko]

More surface area equals greater friction.

[dual fours]

I started out with G60-15's on the rear, F60-15 on the front, on a 70 Dodge Charger SE. Went to Firestone L60-15's on the rear, kept the F's up front, with the L's on, that car accelerated faster and kicked butt faster, covered more ground in less time. Things are never equal! This was back in the late 70's. The Charger still sits this way today. I was a street racer, anything from 1/8 to 1 mile, it was in it's glory, and did what it was meant to be doing, kicking a$$. I say again "THINGS ARE NEVER EQUAL"

[XH29N0G]

Thanks.  I think I am circling around the drain on this one.  The impression I get is that the issue is that tire traction depends on factors in addition to those used to argue for a direct 1:1 trade because  (1) the contact patch increases, but the weight/area on the contact patch decreases and cancels the benefit for the total force that can be applied to acceleration. I suppose the tires are changing in different ways as well (deforming etc..)  it also makes sense because if another aspect ratio worked better, people would probably be using it.

[HeavyFuel]

Too many variables.....


Winter tires are skinny in order to concentrate the weight into a smaller contact area = more grip.   Ever try to go up a snow covered hill on 50's?   

[WhiteOnGreen]

More surface area equals greater friction.

Yes, but more surface area and same weight equal to minor presure for square meter 

[green69rt]

It's not a straight matter of friction between the tire and the pavement.  Modern tires have various degrees of "stickiness" to them.   That's part of the reason high performance tires wear out so quickly.  Rather than rely only on friction for grip the tire actually sticks and in some cases adheres to the road.  When the tire pulls away from the pavement a little of the rubber compound is left behind.  High performance tires are sticker than every day street tires and lose compound at a faster rate.  Drag racer tire manufacturers know this well.

[XH29N0G]

Just thinking  - same compound, same tread to leave that out of it, same pavement, same weight.

My understanding is that physics of force of dry friction  (Force parallel to surface = friction coefficient * normal force) remains constant independent of contact patch, but that in the case of a car tire the situation is more complex.  It might be more complex in part because tires deform and effect weight transfer or in part because of how a larger contact patch might do a better job averaging out variability in the surfaces. 

Assuming wider tires grip better (all else being equal), what I do not know is how much more the wider tire will grip, or what math describes this. 

It is kind of transparent, but I can also put it this way.  If I buy 255 60 15 or 275 60 15 MT drag radials  how much better will the wider ones be?

[cdr]

i told my wife that the bigger 295 50 15 tires are safer, because they get better traction,,she said well you just gotta get those bigger tires.

it worked !!!!!!

[XH29N0G]

i told my wife that the bigger 295 50 15 tires are safer, because they get better traction,,she said well you just gotta get those bigger tires.

it worked !!!!!!

Sounds like something my dad would do...  BUT I think my mom knew very well what he was up to. 

[HPP]

let me ask this,

are doing some sort of racing where an extra .1 reduction in time makes the difference between winning or loosing?

If yes, worry about it and look for more detailed info. If no, then put what looks good and makes you feel good on it.

IMO, 255 to 275 = no difference.

FWIW, according to physics theory, nitro cars should not be able to accelerate as fast as they do.

[XH29N0G]

That makes sense.  Thanks.