This has been bugging me for ages!
I was reading a post the other day where one of the members was saying that he was going to put on some wide tyres to increase his 1/4 mile times.
Now in engineering terms, grip (or frictional resistance) is u(friction co-efficent) times by the force. Notice there is NO allowance for surface area!..... ie/ width of tyre / contact patch.
Despite this, everyone knows that wide tyres grip better! Is this just because a higher grade rubber compound is more likely to be used in a wider (more expensive) tyre?.... Or maybe the size of the tyre allows for better heat dissipation?
I had countless arguments with lecturers / tutors about this subject when I was at uni & have not been satisfied with any explanations offered (There are other friction application that disprove the grip thing).
I'd like to know what any of you guys that are involved with racing or are servicing the automotive industry think.

I have often wondered about this,

The smaller the contact area the greater the pounds per square inch and the larger the contact area the lesser pounds per square inch.

So you would think that narrower tyres would be less likely to slide because they have more weight for surface area to hold them down.

But then I look at Clubmans car and it has massively wide tyres but it only weighs 500kg.

Is there a formula to work out when surface area loses out to downward PSI?

I believe they do and so does the tech section under Suspension. More contact patch. This is part of the reason Formula One cars are quicker than superbikes (considerably) around a track. Four tyres are better than two. That is my theory anyway.

I think the Physics of tread and width keep things the same, But when you involve Adhesion then the equation changes, If you can picture having one spot of glue, its easy to pull apart, but if you spread that over a larger area then it makes the job alot harder.

talking from experience, the difference between 175 and 185 is very noticable with my car, also on a mates vp with 205s it chirpies big time into second with 225s there is nothing. Makes sense to me that the more tyre on the ground the more grip/friction? Braking also improves dramatically with wider tyres

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Until you add some variables, like water, and then the wider the tyre, the quicker you start aquaplaning.

I'm certainly no genius on this issue, but there must be a maximum point at which the benefits of a wider tyre start to become eroded.

In theory there may be a point where going wider looses grip/traction - but you'll have been scrubing the guards then getting flares etc way before that point

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Hmmm... Water with wide tyres can be interesting.

mmmm
believe it or not this is a very tecnical question with many areas of physics coming into play with your final outcome....

there is a book called "how to make your car handle" it is all to so with slip angle...
and also aerodynamic resistance and achieving the best comprimise between the two.
For example, a Formula Ford usually has 14 x 7's with 195 55 14 Avons on board. If they were to have Formula 1 wheels and tyres, they would have better grip but would be slower overall due to weight and increase aero drag.
Everytime you add something you need to realise it always comes at a cost and you need to outweight the benefits with the cost.
If you were to put on space savers better aero but less surface area so less grip around the corners and slower times.

Dragster tyres are designed to be wide a fat for takeoff (increase in surface area) but as speed/rearwheel rpm increases, it narrows due centrifugal force and then surface area diminises....but this is good as there is less inertia meaning less grip is needed and more aero drag, so the frontal is decreased.

Ok then there is the question of side wall construction and also tyre compound and areodynamic lift and you suspension being setup to keep your tyre on its optimal tread pattern.......
this is getting very technical so there is a formula:-

I have to get my book out....back with that formula after dinner........

Not so. (Converted posted at the same time, so this doesn't reference his post)

The formula for calculating "static friction", does not have an "area" component.

Ff = uN

However, when a tyre is under load, the cross-section of the tyre does not have a uniform "static co-efficient of friction", as u (mew) changes with temperature, nor does the tyre have equal force (Newtons) on the crosssection of the tyre on the ground.

So as you can see, it's all rather complex.

The basic reason for having wider tyres is that they last longer (if both are same compound). There is more rubber supporting the load of the car, allowing the tyres to be softer, which changes the u (mew= static friction constant) to be more favourable to grip. The bigger tyres also dissapate the heat better, keeping the crosssectional tyre temperature more consistant.

I believe this is the best tyre explanation.

If tyres didn't get hot, skinny ones would be the best.