Wider Tire = More Grip, right??? Hmm...

[Pitwork]

I'm having a debate with my physics teacher. I contend that, all other variables being equal, a wider tire will produce greater grip in the form of lateral g forces. He disagrees, stating that race cars run wider tires in order to promote cooling of the tire and are therefore able to use softer compound rubber. I can accept that, but has also stated that the size of the contact patch has nothing to do with the "grip" produced. Discuss.

[Clivey]

Originally Posted by Pitwork

I'm having a debate with my physics teacher. I contend that, all other variables being equal, a wider tire will produce greater grip in the form of lateral g forces. He disagrees, stating that race cars run wider tires in order to promote cooling of the tire and are therefore able to use softer compound rubber. I can accept that, but has also stated that the size of the contact patch has nothing to do with the "grip" produced. Discuss.

If what he says were to be true, then why do most "sports" versions of regular road cars run wider tyres as standard?

[coolieman1220]

well i dunno about corners but for going straight it helps but down power better for sure. distributes the weight better. i kno low profile can help so

[NSXType-R]

The surface area's been increased with wider tires.

It should increase grip as well.

That's why old racing slicks had no treads in them at all. Smooth rubber tires throughout.

That's also why they're rubbish when the rain comes. Can't move the water out of them at all so it's extreme hydroplaning.

[deffenbaugh03]

To me it seems like saying that a wider tire doesn't provide more grip then a skinny tire is basically saying that the surface area of the contact patch has no effect on grip. If that were true than it would also be true that if the tire is just barely touching the ground it would provide the same grip as when the tire is firmly planted on the tarmac. I'm pretty sure we all know this isn't true.

[Matra et Alpine]

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

about half way down will explain the different kinds of grip a tyre provides and how deformation under corner weight means that the CONTACT PATCH is not what you expect

btw he's wrong about the race tyres

and an oft missed component on a very wide tyre is that to take a tight turn then the wheel MUST give up traction across a largish area of it's footprint and thus reduces the actual cornering grip that a narrower tyre would have. There are calculable limits to all of these things. ENjoy the ideas the tyre bible will present you and your teacher with

[RacingManiac]

Interesting concept was explained in "The Consultant" section of Racecar Engineering a while back about the merit of wider tire. The common misconception is that wider tire = bigger contact patch area. This is not necessarily true(on the face value), as wider tire just simply means that your contact patch will be shaped differently(at a given tire pressure, narrow tire has a longer contact patch, but narrower, while a wider one is the opposite). However, being a wider tire it gives you a higher tire spring rate, which allows you to run at a lower pressure to get your desired wheel rate, hence the end result of "larger contact patch". While the softer tire spring will generate more heat which may help the compound to operate at its desired temperature, and wider tire do give you more tire "cooling" because of the extra surface area. All this though can vary greatly between car, tire, construction and compound.

[fpv_gtho]

Originally Posted by Pitwork

He disagrees, stating that race cars run wider tires in order to promote cooling of the tire and are therefore able to use softer compound rubber

Race cars use softer compound tyres because they might have to last 100-200km max, depending on what series etc. A road tyre might be expected to do 20-40,000 km's and has to be much harder to be durable enough.

[johnnynumfiv]

Originally Posted by fpv_gtho

Race cars use softer compound tyres because they might have to last 100-200km max, depending on what series etc. A road tyre might be expected to do 20-40,000 km's and has to be much harder to be durable enough.

The cooling effect could be important in some situations. If a very soft compound tire gets too warm the rubber greases over which results in poor performance.

[drakkie]

My car proves very well in the rain, that narrow tires don't have much grip. Almost every traffic light the tires are squeaking no matter how slow you accelarate...

[Wouter Melissen]

Originally Posted by drakkie

My car proves very well in the rain, that narrow tires don't have much grip. Almost every traffic light the tires are squeaking no matter how slow you accelarate...

That's the exceptionally powerful engine working against you; any width tire would get that result.

[ruim20]

Your professor had a bad day i guess, the wider the tire the more grip you have in accelaration and in cornering, the wider the tire the biger the contact patch gets ence more traction in the pavment.

[fpv_gtho]

Originally Posted by drakkie

My car proves very well in the rain, that narrow tires don't have much grip. Almost every traffic light the tires are squeaking no matter how slow you accelarate...

In the rain though width means little in comparison to tread depth and design.

[acfsambo]

If the tyre is wider, the pressure has less of a range. If the pressure is too low than only the outside of the tyre will conatct the pavement, and if it is too high, the middle will be the only part contacting the pavement. So wider tyres can = more grip only if the tyre pressure is right, and for wider tyres, its a smaller band.

My dad's car (XR6T) is reccomended to run 38psi back and 36 front, but optimal is 40 back and 38 fromt. It has low prfile tyres (pretty wide as well). So he has too keep it higher so he doesnt hav to keep checking them as regularly, and so it has better grip (he needs it)

[2ndclasscitizen]

Originally Posted by acfsambo

My dad's car (XR6T) is reccomended to run 38psi back and 36 front, but optimal is 40 back and 38 fromt. It has low prfile tyres (pretty wide as well). So he has too keep it higher so he doesnt hav to keep checking them as regularly, and so it has better grip (he needs it)

235 =/= wide.