Wider Tires = Less Grip ????????????????
Feb 16, 2010, 09:37 PM
#33
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not to get totally off topic but my problem right now is my suspension is TOO tight for what I need.
Tanabe 7 Series Coilovers
Pro 210 Race Springs
Front and Rear Tanabe Chrome-moly Swaybars
Perrin PRSR Kit
Energy Suspension Bushings
Tanabe Camber Plates
Tanabe Underbracing
A full roll cage
Its so tight it understeers a bit with the tires and alignment specs i have now. I do not have a way to adjust the rebound/damning at the moment but the coilovers are set on full stiff.
I need a wider tire I think
Tanabe 7 Series Coilovers
Pro 210 Race Springs
Front and Rear Tanabe Chrome-moly Swaybars
Perrin PRSR Kit
Energy Suspension Bushings
Tanabe Camber Plates
Tanabe Underbracing
A full roll cage
Its so tight it understeers a bit with the tires and alignment specs i have now. I do not have a way to adjust the rebound/damning at the moment but the coilovers are set on full stiff.
I need a wider tire I think
Last edited by MitsoKid; Feb 17, 2010 at 09:15 AM.
Feb 17, 2010, 09:13 AM
#36
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I honestly dont know the spring rates, I bought the coilovers used. But I believe they are somewhere in the ballpark of 12.0/10.0 or 14.0/12.0 front rear
The swaybars are 25mm on the front and 22mm rear on factory endlinks and race bushings
The alignment settings change constantly. But usually
-1.8 camber front, -.16 toe out front. +.5 caster front (I have adjustable camber)
-1.0 camber rear, 0.0 toe rear, OE caster setting rear
I'm still working out on the alignment settings, havn't tweaked them enough. I am interested in what you guys are using with a 255 though.
My car was hit January of 2009 in the rear wheel buy another car. It destroyed the wheel and bearing and I have never been able to adjust my alignment much after that
The swaybars are 25mm on the front and 22mm rear on factory endlinks and race bushings
The alignment settings change constantly. But usually
-1.8 camber front, -.16 toe out front. +.5 caster front (I have adjustable camber)
-1.0 camber rear, 0.0 toe rear, OE caster setting rear
I'm still working out on the alignment settings, havn't tweaked them enough. I am interested in what you guys are using with a 255 though.
My car was hit January of 2009 in the rear wheel buy another car. It destroyed the wheel and bearing and I have never been able to adjust my alignment much after that
Feb 17, 2010, 09:25 AM
#37
For the OT, I think what the Japanese guy is talking about is front to rear tire/grip ratio. If you increase rear grip without increasing front, it makes the car harder to rotate = understeer.
The Japanese tuners get all crazy detailed with that stuff. Sometimes even going wider wheels with the same size tires in the front vs. rear (or vice versa) in order to affect how rapidly the tire looses grip at its threshold.
The Japanese tuners get all crazy detailed with that stuff. Sometimes even going wider wheels with the same size tires in the front vs. rear (or vice versa) in order to affect how rapidly the tire looses grip at its threshold.
Feb 17, 2010, 10:38 AM
#39
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The commonly accepted idea is that contact patch size does not increase with tire width... given all other things being equal, a wider tire will have a wider but shorter(in regards to circumference) contact patch, while a narrower tire will have a narrower but longer contact patch. The actual surface area of said contact patch will not change.
The wider/shorter contact patch does, however, allow for each individual "patch" to be in contact with the ground for a shorter period of time... this means a given contact patch will have more time to cool off before its next encounter with the road surface on a wider tire... while the narrower tire will be getting hotter.
All other things being equal, the narrower tire will not be capable of being pushed as hard for as long because of this.
But, in turn, this also means that a wider tire requires more friction/work to get into its optimal temp range than a narrow tire. If the car cannot generate enough heat into the tires, the wider tire will be running below its ideal temp range, and therefore not generating its potential grip. This is an example of a situation where a narrow tire could provide more grip than a wider tire.
Also... these translations of the Best Motoring/etc videos can sometimes be a little vague and out there. Did these guys actually have a datalogger/accelerometer on board to make a definitive statement that the wider tire is producing less grip? Or did the overall lap time increase so they are making a conclusion that the wider tire = less grip, simply because the lap time is slower?
If the latter, there could be a number of different reasons why the overall lap time was slower with the wider tire. The most obvious being the increased weight and rotational mass... others being a larger overall diameter and therefore gearing/roll-out ratio change.
Edit: It is also important to keep in mind that the actual durometer of the rubber can vary between different sizes of tires from the same manufacturer, due to differences in the molds, date of manufacture, temperature at which the tires were stored, etc.
The wider/shorter contact patch does, however, allow for each individual "patch" to be in contact with the ground for a shorter period of time... this means a given contact patch will have more time to cool off before its next encounter with the road surface on a wider tire... while the narrower tire will be getting hotter.
All other things being equal, the narrower tire will not be capable of being pushed as hard for as long because of this.
But, in turn, this also means that a wider tire requires more friction/work to get into its optimal temp range than a narrow tire. If the car cannot generate enough heat into the tires, the wider tire will be running below its ideal temp range, and therefore not generating its potential grip. This is an example of a situation where a narrow tire could provide more grip than a wider tire.
Also... these translations of the Best Motoring/etc videos can sometimes be a little vague and out there. Did these guys actually have a datalogger/accelerometer on board to make a definitive statement that the wider tire is producing less grip? Or did the overall lap time increase so they are making a conclusion that the wider tire = less grip, simply because the lap time is slower?
If the latter, there could be a number of different reasons why the overall lap time was slower with the wider tire. The most obvious being the increased weight and rotational mass... others being a larger overall diameter and therefore gearing/roll-out ratio change.
Edit: It is also important to keep in mind that the actual durometer of the rubber can vary between different sizes of tires from the same manufacturer, due to differences in the molds, date of manufacture, temperature at which the tires were stored, etc.
Feb 17, 2010, 02:13 PM
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Interesting info!!! Although I dont understand the termenologies of such topic (Patch vs tread contact)...
Can someone explain these terms in dummies language please???
Can someone explain these terms in dummies language please???
Feb 17, 2010, 03:08 PM
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Not picking on any particular poster, but opinions are pretty worthless. Look for data. Autocross cars live on grip. Street Prepared is faster than Stock and they always go to bigger wheels & tires. And the stock guys generally put as much rubber on the car as possible.
And if looking to autocross, only look at the best. The competitive guys at the SCCA National Championships. Like stock mustangs running 295's on 8" (way undersized) rims and going super quick.
Ignoring snow, there is no argument. Bigger is better.... Okay, compound's real important too.
And if looking to autocross, only look at the best. The competitive guys at the SCCA National Championships. Like stock mustangs running 295's on 8" (way undersized) rims and going super quick.
Ignoring snow, there is no argument. Bigger is better.... Okay, compound's real important too.
Feb 17, 2010, 03:12 PM
#43
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So I guess running 255 or 265 wouldn't compromise the 'wanted' additional grip for the car since the Evo weighs more than an S2000!! right??
BUT, how about running extreme summer tires?? Im planning to get either Yukohama AD08 or Dunlop Z1.. These tires usually perform better when they are at higher temps than normal ones, so will these tires (in addition to the wider tires which will require more heat as i understood) compromise the handling and grip???
My aim in such setup is nothing but to add more CORNERING GRIP!!! I love it when I stick to the road with no drama!!! :P
Feb 17, 2010, 03:55 PM
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heres a little more scientific reasoning:
remember a few things, all your forward acceleration, and lateral acceleration is determined by one thing. the force of friction (denoted as Ff)
Ff = mu * Fn
where mu is the coefficient of friction (strictly determined by materials, i.e. soft tire has high mu, hard tire has low mu... if the pavement is ice, mu is extremely low, if pavement is concrete, its higher. mu does change if it is static or kinetic though, but lets set that aside for later).
Fn is the normal force, or in other words the weight on the tire.
if you notice, nowhere in that equation is there area (or contact patch). so the force of friction is not related to the surface contact patch directly. so putting a wider tire of the exact same compound doesn't change traction at all. you do increase contact patch, but you reduce the normal force per sqft. so you might have more area, but the force per area is less. it all comes out to be the same if you were to integrate the load over the area.
surface area DOES play an effect on softer tires though. imagine a new hoosier A6, the tread is gewy, you can stick your finger nails in it, and it feels very soft. this soft rubber has a very low shear strength. basically the material rubs apart very easily. this is why they wear out so fast, the soft rubber has a high mu, but low shear. shear DOES matter on area though, if you distribute the load over a larger area, you reduce the shear stress, and are less likely to rip apart the rubber.
so you now have two situations where you can "lose" traction. one is where the mu isn't enough the two surfaces slip (static to kinetic). this is typical with a very hard rubber, low normal force, or on a slippery surface. there is usually little to no rubber transfered to the pavement. (think of it like rubbing your hand across a smooth laminate counter, you hand slips easily, no matter how hard you push down, you can still slide you hand over it)
the second situation is where the tire grips really well with the pavement, but the tire itself comes apart (shear stress exceeded). this is why race tracks usually have rubber at all the turns or at the start of say a drag strip. the soft tires grip so well the force of friction is greater then the shear stress. (this would be more like rubbing your hand across a sheet of heavy grid sandpaper.... very high mu, and if you push down hard and try slipping your hand over it, more then likely it will cut you or scratch the outerlayer of skin off your hand... so your skin shear stress is less then the force of friction)
so when you wonder why large wings make a difference, the downforce generates more normal force, which increases the force of friction of the tire against the pavement. it doesn't help you at all from a standstill though.
alignment plays a huge part because if a tire is pointed in the wrong direction (bad toe, bump steer etc..) you end up getting two lateral forces pushing against each other constantly. if these lateral forces are large, it reduces the remaining force of friction or shear stress pushing you longitudinally, or in a turn less in the direction you actually want to go). it also increases tire wear, and increases temperatures.
the last consideration was already mentioned, was heat. all tires work best warm. a huge tire will never get up to temp in one lap of an autocross, so running a narrower tire can actually be more effective because it is easier to get up to temp. if your tracking your car and the tires are overheating, a wider tire is most likely needed to distribute the load better and reduce the temp.
if you know why you have no traction, thinking this through can greatly increase you logic when choosing a tire. more often then not, a better tire in the same size will yeild better results then throwing the widest tire you can find on there.
remember a few things, all your forward acceleration, and lateral acceleration is determined by one thing. the force of friction (denoted as Ff)
Ff = mu * Fn
where mu is the coefficient of friction (strictly determined by materials, i.e. soft tire has high mu, hard tire has low mu... if the pavement is ice, mu is extremely low, if pavement is concrete, its higher. mu does change if it is static or kinetic though, but lets set that aside for later).
Fn is the normal force, or in other words the weight on the tire.
if you notice, nowhere in that equation is there area (or contact patch). so the force of friction is not related to the surface contact patch directly. so putting a wider tire of the exact same compound doesn't change traction at all. you do increase contact patch, but you reduce the normal force per sqft. so you might have more area, but the force per area is less. it all comes out to be the same if you were to integrate the load over the area.
surface area DOES play an effect on softer tires though. imagine a new hoosier A6, the tread is gewy, you can stick your finger nails in it, and it feels very soft. this soft rubber has a very low shear strength. basically the material rubs apart very easily. this is why they wear out so fast, the soft rubber has a high mu, but low shear. shear DOES matter on area though, if you distribute the load over a larger area, you reduce the shear stress, and are less likely to rip apart the rubber.
so you now have two situations where you can "lose" traction. one is where the mu isn't enough the two surfaces slip (static to kinetic). this is typical with a very hard rubber, low normal force, or on a slippery surface. there is usually little to no rubber transfered to the pavement. (think of it like rubbing your hand across a smooth laminate counter, you hand slips easily, no matter how hard you push down, you can still slide you hand over it)
the second situation is where the tire grips really well with the pavement, but the tire itself comes apart (shear stress exceeded). this is why race tracks usually have rubber at all the turns or at the start of say a drag strip. the soft tires grip so well the force of friction is greater then the shear stress. (this would be more like rubbing your hand across a sheet of heavy grid sandpaper.... very high mu, and if you push down hard and try slipping your hand over it, more then likely it will cut you or scratch the outerlayer of skin off your hand... so your skin shear stress is less then the force of friction)
so when you wonder why large wings make a difference, the downforce generates more normal force, which increases the force of friction of the tire against the pavement. it doesn't help you at all from a standstill though.
alignment plays a huge part because if a tire is pointed in the wrong direction (bad toe, bump steer etc..) you end up getting two lateral forces pushing against each other constantly. if these lateral forces are large, it reduces the remaining force of friction or shear stress pushing you longitudinally, or in a turn less in the direction you actually want to go). it also increases tire wear, and increases temperatures.
the last consideration was already mentioned, was heat. all tires work best warm. a huge tire will never get up to temp in one lap of an autocross, so running a narrower tire can actually be more effective because it is easier to get up to temp. if your tracking your car and the tires are overheating, a wider tire is most likely needed to distribute the load better and reduce the temp.
if you know why you have no traction, thinking this through can greatly increase you logic when choosing a tire. more often then not, a better tire in the same size will yeild better results then throwing the widest tire you can find on there.