Picking New Tires, Trying To Get More Front Grip

MacCool · 06-29-2015, 06:57 AM

Quote:

Originally Posted by ScottOmatic

If I am doing and processing everything correctly, the only way to get more surface area and thus more grip to the front tires would be going with something like 245/45R 19 or 275/40R 19, everything else that is wider (that is available) is in 35 or 30 sidewall percentage and that actually comes up short compared to the stock size and thus, less surface area and less grip (in theory).

You are making the incorrect assumption that increased contact patch surface area will increase traction or grip. Friction is not dependent on surface area. A wider tire won't get you more grip.

JARblue · 06-29-2015, 08:02 AM

Quote:

Originally Posted by MacCool

You are making the incorrect assumption that increased contact patch surface area will increase traction or grip. Friction is not dependent on surface area. A wider tire won't get you more grip.

All things being equal, an increased contact patch surface area will absolutely increase grip. But it is not the only factor, nor is it necessarily the most important. There are a number of factors that affect grip, many of which directly influence the contact patch surface area. Things like tire pressure, tire temperature, camber, and wheel width can all affect the size of the contact patch.

OP, I agree with the first two responses. Try a 275 square setup and see what that does for you

MacCool · 06-30-2015, 06:16 PM

Quote:

Originally Posted by JARblue

All things being equal, an increased contact patch surface area will absolutely increase grip.

Uh...no, it absolutely will not. The OP is on a fool's errand.

.

Rusty · 06-30-2015, 08:39 PM

Quote:

Originally Posted by MacCool

You are making the incorrect assumption that increased contact patch surface area will increase traction or grip. Friction is not dependent on surface area. A wider tire won't get you more grip.

Quote:

Originally Posted by MacCool

Uh...no, it absolutely will not. The OP is on a fool's errand.

.

Care to explain please.

Brendan · 06-30-2015, 06:54 PM

Quote:

Originally Posted by MacCool

You are making the incorrect assumption that increased contact patch surface area will increase traction or grip. Friction is not dependent on surface area. A wider tire won't get you more grip.

So then what would you recommend?

kenchan · 07-01-2015, 11:04 AM

Quote:

Originally Posted by Brendan

So then what would you recommend?

bicycle tires.

b1adesofcha0s · 07-01-2015, 11:13 AM

Quote:

Originally Posted by kenchan

bicycle tires.

VSS370z · 07-01-2015, 02:01 PM

Quote:

Originally Posted by kenchan

bicycle tires.

Wouldn't motorcycle tires be better optios?

AntiVenom · 07-01-2015, 02:09 PM

Quote:

Originally Posted by VSS370z

Wouldn't motorcycle tires be better optios?

no need to add the extra width. it won't make any difference anyway.

VSS370z · 07-01-2015, 04:29 PM

Quote:

Originally Posted by AntiVenom

no need to add the extra width. it won't make any difference anyway.

Oh damn you're right and i thought those were gonna be better for grip and cornering. Never mind!

jpkirk · 07-06-2015, 04:09 PM

Quote:

Originally Posted by VSS370z

Wouldn't motorcycle tires be better optios?

Too wide and heavy and rolling resistance would increase torsional loads.

Red__Zed · 06-30-2015, 09:11 PM

Quote:

Originally Posted by MacCool

You are making the incorrect assumption that increased contact patch surface area will increase traction or grip. Friction is not dependent on surface area. A wider tire won't get you more grip.

People always say things like this because the Physics 101 equations (F.friction = mu * F.normal) say friction isn't dependent on surface area, but the Coulomb model has a couple of holes in practice, especially in regards to car tires.

Increasing contact patch does help with a tire for a couple of reasons, especially because we are concerned with traction, rather than just friction.

One element is maintaining stability over rough surfaces. A wider tire gives you more opportunity to have rubber in contact with the road, as the tire deforms over imperfections. If you've ever cornered on a road bicycle and hit something mid corner, you'll understand why this is important.

Adhesion plays a role in traction as well. If you slap a piece of tape on your desk and try to slide it, you can see this. It will be very difficult to slide, despite a very minimal normal force acting on it. Adhesion comes into play on car tires as well - there are dozens of SAE papers out there on it, and the Wikipedia page on friction has some links for you as well.

If you really want to get into the weeds on cornering performance, a wider tire also tends to help with slip angle. And of course heat management comes into play.

Other reading:
https://en.wikipedia.org/wiki/Tire_load_sensitivity

ScottOmatic · 06-30-2015, 10:10 PM

Quote:

Originally Posted by Red__Zed

People always say things like this because the Physics 101 equations (F.friction = mu * F.normal) say friction isn't dependent on surface area, but the Coulomb model has a couple of holes in practice, especially in regards to car tires.

Increasing contact patch does help with a tire for a couple of reasons, especially because we are concerned with traction, rather than just friction.

One element is maintaining stability over rough surfaces. A wider tire gives you more opportunity to have rubber in contact with the road, as the tire deforms over imperfections. If you've ever cornered on a road bicycle and hit something mid corner, you'll understand why this is important.

Adhesion plays a role in traction as well. If you slap a piece of tape on your desk and try to slide it, you can see this. It will be very difficult to slide, despite a very minimal normal force acting on it. Adhesion comes into play on car tires as well - there are dozens of SAE papers out there on it, and the Wikipedia page on friction has some links for you as well.

If you really want to get into the weeds on cornering performance, a wider tire also tends to help with slip angle. And of course heat management comes into play.

Other reading:
https://en.wikipedia.org/wiki/Tire_load_sensitivity

Thanks,

I was just searching most of the points you have made here a half hour ago, lot's of things going on here.

Another interesting factor that I saw brought up was viscoelasticity. Tires are not simple creatures.

MacCool · 07-01-2015, 08:14 AM

Quote:

Originally Posted by Red__Zed

People always say things like this because the Physics 101 equations (F.friction = mu * F.normal) say friction isn't dependent on surface area, but the Coulomb model has a couple of holes in practice, especially in regards to car tires.

Increasing contact patch does help with a tire for a couple of reasons, especially because we are concerned with traction, rather than just friction.

One element is maintaining stability over rough surfaces. A wider tire gives you more opportunity to have rubber in contact with the road, as the tire deforms over imperfections. If you've ever cornered on a road bicycle and hit something mid corner, you'll understand why this is important.

Adhesion plays a role in traction as well. If you slap a piece of tape on your desk and try to slide it, you can see this. It will be very difficult to slide, despite a very minimal normal force acting on it. Adhesion comes into play on car tires as well - there are dozens of SAE papers out there on it, and the Wikipedia page on friction has some links for you as well.

If you really want to get into the weeds on cornering performance, a wider tire also tends to help with slip angle. And of course heat management comes into play.

Other reading:
https://en.wikipedia.org/wiki/Tire_load_sensitivity

Slip angle, rough surface traction, heat management, and therefore cornering performance, assuming you're pushing it hard enough to generate that much heat that it matters, are absolutely valid points in the discussion of traction vs friction. The OP is contemplating differing tires sizes to manage understeer/oversteer. Those factors don't come into play. He want's to "loosen it up" and "free it up a little more by getting more contact with the road with the front tires". We're back to high school physics.

Red__Zed · 07-01-2015, 08:45 AM

Quote:

Originally Posted by MacCool

Slip angle, rough surface traction, heat management, and therefore cornering performance, assuming you're pushing it hard enough to generate that much heat that it matters, are absolutely valid points in the discussion of traction vs friction. The OP is contemplating differing tires sizes to manage understeer/oversteer. Those factors don't come into play. He want's to "loosen it up" and "free it up a little more by getting more contact with the road with the front tires". We're back to high school physics.

You're neglecting adhesion in your response. And oversteer/under steer is just f/r management of traction...

That basic equation assumes minimally elastic solids. Surface area matters more as the material becomes more elastic.

There are a lot of good resources to school up on traction out there. I'd recommend taking a look.

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