Why are wider tyres grippier?

Hamzter · 18 Jul 2008 at 22:01

Now this will inevitably result in a rush of people claming that they have more grip because the contact area is bigger, but I'm afraid this isn't the right answer. The real answer is much more complex, I'm interested to what everyone thinks though as there seems to be a range of explanations! So why do you think wider tyres are grippier?

[TW]Fox · 18 Jul 2008 at 22:02

The wider your tyres are, the cooler your car is, obviously the faster it is and the more girls will think you are awesome.

Grip is simply a side benefit.

Joe T · 18 Jul 2008 at 22:04

Hamzter said:
The real answer is much more complex,

Are you going to tell us then? Or are you just trolling for laughs?

2Thumbs · 18 Jul 2008 at 22:05

mavity.

Not as much grip as putting your back seats down though.

Hunders · 18 Jul 2008 at 22:06

I'll be honest here and say that I always thought it was down to a bigger contact patch.

hardc0re_tid · 18 Jul 2008 at 22:10

it depends, wider tyres arent grippier in snow

Gaygle · 18 Jul 2008 at 22:11

Me too ^^^

But i also knew that just because a car had wider tyres, didn't mean it was a grippy car.

A stab in the dark....anything to do with the weight of the car over more of the tyre?

benjo plz. · 18 Jul 2008 at 22:13

With snow etc thinner tyres are better at cutting into the mud below.

Hunders said:
I'll be honest here and say that I always thought it was down to a bigger contact patch.

surface area you mean

.

Vasquez · 18 Jul 2008 at 22:15

don't heat up as much?

Flukester · 18 Jul 2008 at 22:16

Gaygle said:
Me too ^^^

But i also knew that just because a car had wider tyres, didn't mean it was a grippy car.

A stab in the dark....anything to do with the weight of the car over more of the tyre?

in a way.... but the same weight is disributed across all tyres no matter what, though to different degrees.

as far as I can see.. grip is down to -

contact area with surface

ability to grip said surface by compound used (softer tyres allow surface to 'dig in' ?)

weight distribution of car changing grip between front / rear / left / right

suspension, this must keep the tyre on the road as much as possible even when surface not level and on corners

the weird thing about corners as far as I can see is if car rolls towards outside of corner the transfer of weight increases grip on the tyres on outside of corner to such a extent I guess it would grip better than if the car had no body roll at all ?, though of course car becomes uncontrollable even though still gripping so you need to strike a balance.

i know on a bike the front brake transfers pretty much all the bike weight / momentum (err kinetic energy ?) to front tyre meaning you have almost unlimited 'grip' on a very small contact area...

hum, thinking about this more the op is right, it's VERY complex, im drunk and I'm gonna have a meltdown thinking about it lol

Hunders · 18 Jul 2008 at 22:18

benjo plz. said:
surface area you mean .

Nope. Contact patch was what I meant

Hamzter · 18 Jul 2008 at 22:19

Joe T said:
Are you going to tell us then? Or are you just trolling for laughs?

Hehe, yeh I'll tell you how I understand it works, but after I've heard other peoples theories, there could well be multiple explanations! Maybe I should just point out why the contact patch is (roughly) the same, the tyre is flexible, so it deforms so that the contact pressure between the tyre and the road is the same as the tyre pressure. Pressure = Force/Area, since the tyre pressure and force (roughly 1/4 the weight of the car) are constant, area is also constant. This means that tyres have the same contact area irrespective of size, the only think that changes is the shape of it.

I think Fox's theory is the winner tho

Bear · 18 Jul 2008 at 22:21

Hamzter said:
Now this will inevitably result in a rush of people claming that they have more grip because the contact area is bigger, but I'm afraid this isn't the right answer. The real answer is much more complex, I'm interested to what everyone thinks though as there seems to be a range of explanations! So why do you think wider tyres are grippier?

They arent, if the rolling radius and tyre pressure is the same. The level of grip is approximately the same just in different directions.

Gaverick · 18 Jul 2008 at 22:26

Some Random Site said:
The reason for wider tires is not that the increased contact area automatically leads to more friction (though there may be some effects that depend on the area indirectly). The design parameter that determines the coefficient of friction between the tires and the track is the something related to the molecular compressibility of the rubber. In other words, "the softer the rubber, the better the friction." However, when you use a softer rubber, you need to make the tires wide enough to give them strength. So, "the softer the tire, the wider it needs to be", to withstand design forces and moments.

benjo plz. · 18 Jul 2008 at 22:26

Hunders said:
Nope. Contact patch was what I meant

nope, you meant surface area. :JediMindTrick:

Flukester · 18 Jul 2008 at 22:28

Bear said:
They arent, if the rolling radius and tyre pressure is the same. The level of grip is approximately the same just in different directions.

I dont think thats true...

corner a car with 6ft wide tyres, I don't think it will slide same time as car with 1inch tyres of same radium and presure.

though the radius is same the actual contact area will be bigger on the wider tyre (read longer) ..will grip more surface, and be grippier. the more 'road' you can hold on to.. the better, though suspension / chassis must be able to handle the width of your tyre so I guess there is practical limits on how wide you can go without turning your car into a bad handling piece of junk not to mention the way it would wear unevenly.

MikeHunt79 · 18 Jul 2008 at 22:31

Looks at rally cars - they use thin tyres in gravel and snow, yet on the tarmac stages they use low-profile wide tyres - maybe slicks if it's dry.

Sooo, it depends on the surface, wider tyres aren't always grippier otherwise we'd have 3ft wide tyres!

Hamzter · 18 Jul 2008 at 22:34

Gaverick said:
Some Random Site said:

The reason for wider tires is not that the increased contact area automatically leads to more friction (though there may be some effects that depend on the area indirectly). The design parameter that determines the coefficient of friction between the tires and the track is the something related to the molecular compressibility of the rubber. In other words, "the softer the rubber, the better the friction." However, when you use a softer rubber, you need to make the tires wide enough to give them strength. So, "the softer the tire, the wider it needs to be", to withstand design forces and moments.

Click to expand...

How does a wider tyre have more strength? I would have thought thinner tyres would be stronger, although it would wear slower because of the larger tyre surface area.

Bear · 18 Jul 2008 at 22:35

Flukester said:
I dont think thats true...

corner a car with 6ft wide tyres, I don't think it will slide same time as car with 1inch tyres of same radium and presure.

though the radius is same the actual contact area will be bigger on the wider tyre (read longer) ..will grip more surface, and be grippier. the more 'road' you can hold on to.. the better, though suspension must be able to handle the width of your tyre so I guess there is practical limits on how large you should go.

No, if the rolling radius is the same and the tyre pressure is the same then the contact patch is roughly the same, just different shape. The car is still the same weight and the tyre pressures are still the same therefore the tyres will still have the same pound per square inch contact on the floor, it cant increase as nothing has changed.

A skinny tall tyre will give more grip going forwards and a wide low profile tyre will give more grip round corners but the level of grip is pretty much the same just in different directions.

Lashout_UK · 18 Jul 2008 at 22:37

Dry traction
Dry traction is measure of the tire’s ability to deliver traction, or grip, under dry conditions. Dry traction increases in proportion to the tread contact area. Dry traction is also a function of the tackiness of the rubber compound.

[edit] Wet traction
Wet traction is measure of the tire’s ability to deliver traction, or grip, under wet conditions. Wet traction is improved by the tread design’s ability to channel water out of the tire footprint and reduce hydroplaning. However, tyres with a circular cross-section, such as those found on racing bicycles and motorcycles, when properly inflated have a sufficiently small footprint to not be susceptible to hydroplaning. For such tires, it is observed that fully slick tyres will give superier traction on both wet and dry pavement.[11]

[edit] Force variation
The tire tread and sidewall elements undergo deformation and recovery as they enter and exit the footprint. Since the rubber is elastomeric, it is compressed during this cycle. As the rubber deforms and recovers it imparts cyclical forces into the vehicle. These variations are collectively referred to as Tire Uniformity. Tire Uniformity is characterized by Radial Force Variation (RFV), Lateral Force Variation (LFV), and Tangential Force Variation. Radial and Lateral Force Variation is measured on a Force Variation Machine at the end of the manufacturing process. Tires outside the specified limits for RFV and LFV are rejected. In addition, Tire Uniformity Machines are used to measure geometric parameters including Radial Runout, Lateral Runout, and Sidewall Bulge in the tire factory at the end of the manufacturing process as a quality check.