Advanced Engineering Tech - Front tire width

Im wondering why the front tires on my camaro are 275mm wide.

Why do F430's, M3's, IS-F's run 225's and my camaro has 275's?

I thought you'd want a wide front tire to maximize grip and minimize understeer.

Would my car handle better/worse/same with 245 tires in the front?

Thanks

ill bet it would handle a whole hell of alot better if u posted this in the right section

Sorry, I figured motion specific vehicle dynamics was complex enough to ask about in the engineering section.

i think it comes down to tire compound and the area of contact soo if u had the same kind of tire in theory the wider one should provide more friction ie traction

I think it comes down to your application and a balance of pros and cons. If you are worried more about straight line acceleration or are you more worried about traction while cornering? If the former, then a 275 is on the big side. If the latter, then a 275 is probably a good choice (look at formula 1 cars; they have massive front tires as well as rears). If you are looking for a little of both, then a 245 is probably a good choice.

For middle-engine cars, they got a lot less weight up front so they just don't need it. It's easier to drive (no tremlining) so that's the Lexus explanation. Bigger isn't always better. You want tires as big as your weight on them requires them to be. Otherwise you don't want them to be too big because that's too much air and rolling resistance. Few years ago GT1 or GT2 Vettes gained some laptimes at LeMans (extremely long straights) because they went to the smaller front tires.

That's what i wasn't thinking of. The weight distribution. Thanks

Im wondering why the front tires on my camaro are 275mm wide.

Why do F430's, M3's, IS-F's run 225's and my camaro has 275's?

I thought you'd want a wide front tire to maximize grip and minimize understeer.

Would my car handle better/worse/same with 245 tires in the front?

Thanks

1) Over 55% of the Camaro's weight is on the front wheels, vs. closer to 42-45% on mid engine cars and 50% on M3. Tires are sized by weight they carry. A C5 Vette carries about 1600 lb. on the 245 fronts and your Camaro carries about 1900 lb. Do the math of M3, IS-F, etc.

2) Fronts do about 60-65% of the cornering work and 75%+ of the braking in a max performance stop on the Camaro. Bigger section = bigger footprint = more traction.

3) The LS1 Camaro needs the 275s on the rear for traction.

4) GM had no intention of having different front/rear wheels and tires on your Camaro.

5) 245s only on the front would increase understeer (push) and lengthen stopping distances in max situations. Not a wonderful idea in my book.

If you really wanted it to corner well and be better balanced on the track, you would increase the size of the fronts to 295 and leave the rears at 275. You might even go 315/275 on really tight tracks. It helps get the back end around.

You won't see a lot of Camaro racers go bigger on the fronts...but you may see it on those who win.

Jon

1) Over 55% of the Camaro's weight is on the front wheels, vs. closer to 42-45% on mid engine cars and 50% on M3. Tires are sized by weight they carry. A C5 Vette carries about 1600 lb. on the 245 fronts and your Camaro carries about 1900 lb. Do the math of M3, IS-F, etc.

2) Fronts do about 60-65% of the cornering work and 75%+ of the braking in a max performance stop on the Camaro. Bigger section = bigger footprint = more traction.

3) The LS1 Camaro needs the 275s on the rear for traction.

4) GM had no intention of having different front/rear wheels and tires on your Camaro.

5) 245s only on the front would increase understeer (push) and lengthen stopping distances in max situations. Not a wonderful idea in my book.

If you really wanted it to corner well and be better balanced on the track, you would increase the size of the fronts to 295 and leave the rears at 275. You might even go 315/275 on really tight tracks. It helps get the back end around.

You won't see a lot of Camaro racers go bigger on the fronts...but you may see it on those who win.

Jon

ALL the fast road race F Body cars run 315 section tires square on a 17x11 if its allowed, 50mm offset in the rear, 36 mm in front making the track wider. It looks kinda goofy bit it works.

http://www.musclecarsoforlando.100megs25.com/jeff/Road%20Atlanta/RA3.jpg

Thank you very informative.

ALL the fast road race F Body cars run 315 section tires square on a 17x11 if its allowed, 50mm offset in the rear, 36 mm in front making the track wider. It looks kinda goofy bit it works.

It's my car in the picture above so I'll chime in. I've been running the 315's all around for a while now and can attest to the fact that they have more mechanical grip than 275's and of course the 245's that I've run in years past. I'm currently experimenting with 295's on 18" diameter wheels to see if less rolling resistance but also less contact patch will be faster. They feel great but the next time trial won't be until June at Sebring so I'll know then and pass it on.

Hey FASTFATBOY, please don't call the old girl goofy looking as she is very sensitive.:D

Size of the contact patch doesn't change with the size of the tire - only the shape. In a stock vehicle, there are lots of compromises made, and the marketing team gets far more say than they should - bigger isn't always better, but damn near 95% of the time, it sells more - right?? In a track car application, temps are far more important. LMP cars, for example, run 3 infrared temp sensors per tire so the engineers can constantly monitor tire temps. Tire width is more appropriately sized for the desired SHAPE of the contact patch, and the amount of heatshed ability you need for the given applied force.

Size of the contact patch doesn't change with the size of the tire - only the shape. In a stock vehicle, there are lots of compromises made, and the marketing team gets far more say than they should - bigger isn't always better, but damn near 95% of the time, it sells more - right?? In a track car application, temps are far more important. LMP cars, for example, run 3 infrared temp sensors per tire so the engineers can constantly monitor tire temps. Tire width is more appropriately sized for the desired SHAPE of the contact patch, and the amount of heatshed ability you need for the given applied force.


This applies if you have control over the tire's orientation to the tarmac. If rules restrict suspension geometry modifications, and wheel width and suspension springs and anti-roll bar(s), much of which happens in "Stock" racing classes, means that you have very little control of the tire's orientation. Controlling or maximizing the dynamic tire patch in this situatiion is the challenge.

The 4th Gen Camaro is a good example of the above, especially in Auto-X. Basically all suspension and wheels have to be stock with the exception of the front A/R bar, shocks and (racing) tire size. That basically means you can increase/decrease front roll couple. Period. Stock front camber curve sucks for racing at stock ride height and 1.0+ lateral G definitely moves the suspension.

Seeing a well setup Stock Class Camaro take a PAX win on a Go-Kart track might make some believers in out-of-the box thinking with tires, etc. It was the longest wheelbase, heaviest car running, but it won. Definitely an E-Ticket ride for a passenger. OK, most readers here probably are not old enough to have experienced Disney "E-tickets". ;)

Sometimes getting creative with tire choices can help folks get around a track quicker.


Jon

Size of the contact patch doesn't change with the size of the tire - only the shape. In a stock vehicle, there are lots of compromises made, and the marketing team gets far more say than they should - bigger isn't always better, but damn near 95% of the time, it sells more - right?? In a track car application, temps are far more important. LMP cars, for example, run 3 infrared temp sensors per tire so the engineers can constantly monitor tire temps. Tire width is more appropriately sized for the desired SHAPE of the contact patch, and the amount of heatshed ability you need for the given applied force.

I disagree, you say a 235/55/16 on a 8 inch wheel has the same contact patch as 315/35/17 on an 11 inch wheel? Regardless of shape?

If that's the case why does an fbody get around the track quicker with a wider front tire? I understand there is a. point of diminishing returns but the car is quicker because there is more tire down on the ground for more turning load, ie more mechanical grip(when set up properly for more grip).

I disagree, you say a 235/55/16 on a 8 inch wheel has the same contact patch as 315/35/17 on an 11 inch wheel? Regardless of shape?

If that's the case why does an fbody get around the track quicker with a wider front tire? I understand there is a. point of diminishing returns but the car is quicker because there is more tire down on the ground for more turning load, ie more mechanical grip(when set up properly for more grip).



Nope. The larger tire is supporting the same amount of weight of the vehicle, therefore is applying the same amount of force upon the tire. Larger tire will yield less psi of pressure per unit area. Think about it with balloons. Think 2 balloons, one smaller, and one larger. With the same force applied to both balloons, which one will have the same area of contact patch to the table? (hint - the contact patches are equal area, different shape!)

And why faster around a track - lots of reasons. Heatshed, suspension geometry, springrate (and along with it, effective wheelrate), etc. Using different sized tires front to rear can alter the dynamics of the vehicle. The BMW E36 M3 is a great example. The '95 M3 had a square wheel setup, 235/40/17 all around on a 17x7.5" wheel. '96-'99 they changed the fronts to a 225/45/17, and the rears to a 235/40/17 on a 17x8.5" wheel. What did the later car do - understeer more.

If you choose not to believe me, here's a thread from bimmerforums with a couple of ALMS engineers (techno550, & steved033). Please, argue with the principles of physics with people WITH physics degree's who help win championships for major pro racing.

http://forums.bimmerforums.com/forum/showthread.php?p=2667862

and now we all know why this thread is in advanced tech :cool:

interesting stuff; i always had 295s up front just for d$%k measuring

If you choose not to believe me, here's a thread from bimmerforums with a couple of ALMS engineers (techno550, & steved033). Please, argue with the principles of physics with people WITH physics degree's who help win championships for major pro racing.

http://forums.bimmerforums.com/forum/showthread.php?p=2667862

The BMW is proving my point, the smaller tire on the front is causing the push.

If this is the case why did Acura invest so much in ALMS cars to run a square tire setup front to rear and win with it? They developed an entirely new steering setup to run a square tire setup?

I could see what you are saying in a static state, but you run a 3900lb FRONT ENGINE car into turn 1 at Barber that has a split weight bias to the front as Mr Jon stated you WANT more tire on the front to help the push(understeer) these cars inherently have. Most cars have understeer built in from the their makers because it is safer.


Dont forget, when you start fooling with tires sizes you MUST fool with other suspension parts to take advantage of the tires. The game changes completely with a road course car when you start fooling around with bigger sizes and more grip.

Just a funny quip, Wally Dallenbach was asked at the Indycar race at Barber to explain understeer and oversteer to the tv audience.........

Wally said" Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car" I laughed my ass off.

The BMW is proving my point, the smaller tire on the front is causing the push.

If this is the case why did Acura invest so much in ALMS cars to run a square tire setup front to rear and win with it? They developed an entirely new steering setup to run a square tire setup?

I could see what you are saying in a static state, but you run a 3900lb FRONT ENGINE car into turn 1 at Barber that has a split weight bias to the front as Mr Jon stated you WANT more tire on the front to help the push(understeer) these cars inherently have. Most cars have understeer built in from the their makers because it is safer.


Dont forget, when you start fooling with tires sizes you MUST fool with other suspension parts to take advantage of the tires. The game changes completely with a road course car when you start fooling around with bigger sizes and more grip.

Just a funny quip, Wally Dallenbach was asked at the Indycar race at Barber to explain understeer and oversteer to the tv audience.........

Wally said" Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car" I laughed my ass off.

LOL, I've read that before. And I'm not trying to say that a smaller tire is better, or that bigger tires are bad. All I'm saying is that there is a 'right' size for every application, and simply saying wider is better is flat-out wrong. As well as stating that a bigger tire has a bigger contact patch, which is also wrong. With a given force applied, there is ALWAYS going to be the same area of contact patch to the road. Tire size is just going to determine the shape of that contact patch.

LOL, I've read that before. And I'm not trying to say that a smaller tire is better, or that bigger tires are bad. All I'm saying is that there is a 'right' size for every application, and simply saying wider is better is flat-out wrong. As well as stating that a bigger tire has a bigger contact patch, which is also wrong. With a given force applied, there is ALWAYS going to be the same area of contact patch to the road. Tire size is just going to determine the shape of that contact patch.

So you are saying I can take the 275-40-17 off the front of my track day 99 z28, take the front runners off the front of the car below in my Sig pic and just as fast around Barber?

Same contact patch ?

So you are saying I can take the 275-40-17 off the front of my track day 99 z28, take the front runners off the front of the car below in my Sig pic and just as fast around Barber?

Same contact patch ?

Same contact patch AREA, yes. The skinnies will overheat quickly though. Not much surface area to dissipate heat. There's more to it than simply bigger is better, and THAT is the part most people seem to skip over so easily. Go too big and you'll never get them up to temp. Compound also makes a huge difference. Sidewall height, slip angles (which are also relative to tread width), etc. Even if, surface area has nothing to do with friction.

Ok, I will agree to disagree.

...
As well as stating that a bigger tire has a bigger contact patch, which is also wrong. With a given force applied, there is ALWAYS going to be the same area of contact patch to the road. Tire size is just going to determine the shape of that contact patch.You are contradicting your statements... if tire size (width and height) determine the shape of the contact patch, how can the area of the contact patch always be the same for different tire sizes...?

Consider two 26" tall tires (i.e. same height), one has 100mm wide tread, the other has 300mm wide tread... there is no way that the contact patch area is the same.

The force on each of those tires will be the same, but the spread of the force will be different (force divided by area), the skinny tire will sink in sand, the fat tire will float on sand.

You are contradicting your statements... if tire size (width and height) determine the shape of the contact patch, how can the area of the contact patch always be the same for different tire sizes...?

Consider two 26" tall tires (i.e. same height), one has 100mm wide tread, the other has 300mm wide tread... there is no way that the contact patch area is the same.

The force on each of those tires will be the same, but the spread of the force will be different (force divided by area), the skinny tire will sink in sand, the fat tire will float on sand.

Your second statement isn't really pertinent to our conversation, tire dynamics on non-paved roads are a bit different. This debate was centered on the assumption (at least I thought so, if we want to introduce even more variables to confuse ourselves with, be my guest) that we're talking about tires on paved roads or racetracks. And no, I contradicted nothing. Considering 2 26" tall tires, one being 300mm wide, one being 100mm wide, and the same applied force - yes, the AREA (in square inches, square centimeters, however you want to measure it) will be identical. The 300mm wide tire will have a wide, but longitudinally narrow contact patch, whereas the 100mm tire will obviously have a narrower, but longitudinally longer contact patch (picture them as rectangles).

Your second statement isn't really pertinent to our conversation, tire dynamics on non-paved roads are a bit different. This debate was centered on the assumption (at least I thought so, if we want to introduce even more variables to confuse ourselves with, be my guest) that we're talking about tires on paved roads or racetracks. And no, I contradicted nothing. Considering 2 26" tall tires, one being 300mm wide, one being 100mm wide, and the same applied force - yes, the AREA (in square inches, square centimeters, however you want to measure it) will be identical. The 300mm wide tire will have a wide, but longitudinally narrow contact patch, whereas the 100mm tire will obviously have a narrower, but longitudinally longer contact patch (picture them as rectangles).Yes, of course, paved roads.

Yes, I am familiar with various units of measurement of area.

Are you assuming the 100mm wide tire has no air in it...? They're both the same height i.e. have the same radius.

Consider this: what if you have three 100mm wide tires (on wheels) stacked together (a dualie plus one, if you will)... the total width is approximately 300mm, how does the total contact area compare...?

If you choose not to believe me, here's a thread from bimmerforums with a couple of ALMS engineers (techno550, & steved033). Please, argue with the principles of physics with people WITH physics degree's who help win championships for major pro racing.

http://forums.bimmerforums.com/forum/showthread.php?p=2667862The tire technical discussion going on at that forum supports the contact area being different with differing tire size, and you're quoting that link as supporting your statement that the contact patch area is independent of tire size.

What they are saying at that forum is that friction is not dependent on tire size, and that the load on the tire is the same regardless of the contact area, so the wider tire has a smaller per unit area loading (meaning that it can support a larger load than the skinny tire)... did you read the technical tidbits at that forum, I think you missed some of what was said (with all due respect, of course).

Yes, of course, paved roads.

Yes, I am familiar with various units of measurement of area.

Are you assuming the 100mm wide tire has no air in it...? They're both the same height i.e. have the same radius.

Consider this: what if you have three 100mm wide tires (on wheels) stacked together (a dualie plus one, if you will)... the total width is approximately 300mm, how does the total contact area compare...?

The tire technical discussion going on at that forum supports the contact area being different with differing tire size, and you're quoting that link as supporting your statement that the contact patch area is independent of tire size.

What they are saying at that forum is that friction is not dependent on tire size, and that the load on the tire is the same regardless of the contact area, so the wider tire has a smaller per unit area loading (meaning that it can support a larger load than the skinny tire)... did you read the technical tidbits at that forum, I think you missed some of what was said (with all due respect, of course).

:pimp:

I have to agree, you're right. I don't know why I was thinking that, thats always the way I understood it from them explaining it in person. Larger tire - larger contact patch, less force per unit area than a smaller tire.