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

[drakkie]

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

True. When up to speed, it clearly has less aquaplaning then some other cars. Stationary it is a fairly big problem, as i tend to drive swiftly.

[Quiggs]

235 =/= wide.

Wide.

[culver]

I suspect your professor was probably correct but not getting his point across. I recall a few times when I was in school where a prof would be answering a question. I knew what was being asked. I knew what the prof was saying. The question and answer weren't related.

You are correct that wider tires generally result in more grip but it’s not as simple as wider = better.

In a sense your prof is right as the shape of the contact patch is very important. In general if you have a wide or narrow tire if you put the same 30psi of air in the tire you will have the same contact patch surface area. The difference is the shape of the contact patches.

He is also right about cooling a race tire. They can over heat.

Where things get muddy is a wider tire can allow you to run a lower pressure tire. Now you can get more area. Now more area results in lower contact patch pressure. Now you can run a stickier rubber.

So basically what you are saying is true but he is actually adding some of the dots that get you from wider tires to more grip.

[Kultag]

Btw. why do they raise the wheels of trucks when they are not loaded? I always thought that it's to increase the pressure under the remaining wheels so they could have a better traction for braking. (In other words: because of the big difference between loaded and unloaded weight.) Am I right?

[Quiggs]

There's regulations on tonnage per axle.

[macoran]

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...

squeaking ?? they may need some grease !

[Clivey]

Btw. why do they raise the wheels of trucks when they are not loaded? I always thought that it's to increase the pressure under the remaining wheels so they could have a better traction for braking. (In other words: because of the big difference between loaded and unloaded weight.) Am I right?

If the truck's unladen, you require less tyre contact to distribute the weight of the vehicle correctly. The advantage of raising the wheels is that the truck then becomes more manoeuvrable because less tyres are "scrubbing" aling the road as it turns and you save tyre wear on the unloaded tyres. At least, that's how I understand it.

[RacingManiac]

I suspect your professor was probably correct but not getting his point across. I recall a few times when I was in school where a prof would be answering a question. I knew what was being asked. I knew what the prof was saying. The question and answer weren't related.

You are correct that wider tires generally result in more grip but it’s not as simple as wider = better.

In a sense your prof is right as the shape of the contact patch is very important. In general if you have a wide or narrow tire if you put the same 30psi of air in the tire you will have the same contact patch surface area. The difference is the shape of the contact patches.

He is also right about cooling a race tire. They can over heat.

Where things get muddy is a wider tire can allow you to run a lower pressure tire. Now you can get more area. Now more area results in lower contact patch pressure. Now you can run a stickier rubber.

So basically what you are saying is true but he is actually adding some of the dots that get you from wider tires to more grip.

Ditto...

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.

[Big time]

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.

Teachers are useless.
Try the real world instead:
Drive a car on a skidpad and measure Gs.
Then fit wider rims/tires and measure Gs again.
Wider tires rule.

By the way it's not about friction, at least not before the tires reach their grip limit.
Rubber behaves differently than other physical compounds (including friction)
That's why rubber has never been replaced for tires.
i.e. you will never see metallic or plastic tires.

[Matra et Alpine]

^^ NOT always, it completely depends on the ability of the suspension to maintain contact shape.
Too wide a tyre can often mean LESS grip and complex affects in straight line versus cornering traction.

As you say it's not JUST about friction as tyres have two differnet modes of "grip".
Too wide a tyre can introduce a contact patch which is very wide but not very long and that is not ideal for acceleration forces affecting the grip.

All materials have friction and physical grip components. Just not as good as rubber for our current needs

BUt this is one of the older threads on the topic. A search will bring up newer discussion and links to study/experiences.

WELCOME

[drakkie]

A good way to calculate is using the "magic formula" by Hans Pacejka. If you are really interested, PM me and I will give you the email adress of my teacher. He used to be working with Pacejka for years and can explain you much better than me.

[Matra et Alpine]

ADAMS/Tire Help

Gives lots more of the math - and alternatives ( and importabtly when they work best and dont work )

[drakkie]

ADAMS/Tire Help

Gives lots more of the math - and alternatives ( and importabtly when they work best and dont work )

Yep. On school we did some work with Adams. Unfortunately not this Tire-tool but I noticed it before. I've been wanting to check it out more thoroughly but I guess my free time is pretty limited and I am more interested in beer + sex

[Matra et Alpine]

^^^^ NEARLY believed you Drakkie till you mentioned the "s" word
DIY doesn't count !!!

( advance apologies, I'm in a Jeremy-mood today and just couldn't stop myself typing the above )

[drakkie]

^^^^ NEARLY believed you Drakkie till you mentioned the "s" word
DIY doesn't count !!!

( advance apologies, I'm in a Jeremy-mood today and just couldn't stop myself typing the above )

Hehe I've been away for a while but I have a girlfriend now for more than a year DIY can be nice, but it's always better when you have someone do it for you

By the way, do you have some experience with building a model in Adams/Tire ? I could use some help to make a jump-start in understanding how to simulate with it.