Why? Ever see the sidewalls on a Formula 1 car, and Indy car? I know the argument is that the lower the sidewall height the faster the turn in response will be (less sidewall flex), but you are giving up suspension compliance (through the tires air pressure). NASCAR figures that each pound of air pressure is equal to 10 pounds of spring rate (with their size tires). Their tires have high sidewalls also.

Now Formula 1 and CART use the tires sidewall flex as part of the suspension travel and I believe HONDA tuned the S2000 suspension in a similar manner.

Your Thoughts?

 

I just did it for looks, so it may or may not have hindered performance.

 

Hi Bieg

My other car is a Legend LS 6 speed coupe. I "upgraded" with a wheels/tires package - 17x7 TSW Trophies shod with 215 45 17 Z rated Dunlop SP9000s. Turn in was beautiful. Handling for a car that large was terrific. I bent 2 complete sets of rims (total 8 wheels). There just wasn't enough tire between road and rim and that was with 45s!. I also think that although TSW stood behind their wheels, those wheels were not so strong. Anyway, I went with 215 50 17 Toyo Proxes T1Ss. Not so low profile, and no problems with my TSW Revo rims. Bottom line for me ... I don't trust ultra low profile wheel/tire combos for street use.

 

According to FIA 2001 FORMULA ONE TECHNICAL REGULATIONS.

12.4 Wheel dimensions :
12.4.1 Complete wheel width must lie between 305 and 355mm when fitted to the front of the car and between
365 and 380mm when fitted to the rear.
12.4.2 Complete wheel diameter must not exceed 660mm when fitted with dry-weather tyres or 670mm when
fitted with wet-weather tyres.
12.4.3 Complete wheel width and diameter will be measured horizontally at axle height when fitted with new
tyres inflated to 1.4 bar.
12.4.4 Wheel bead diameter must lie between 328 and 332mm.

Which means the wheel can be no larger than 14inches and the tires can not be larger than 26 inches. Which explained a small wheel and large side wall length. Do not be fooled, those tires sidewall are very stiff. I was moving some tires in my garage today. The side wall of my stock S02 is much softer than my Yoko A032R tires. You will notice a real stiff chassis when you put A032R on your car.

For my personal preference, I like a stiffer suspension. Changing to race tire and remain stock size wheel makes my car stiffer on the road and make the car more agile on the street and race tracks. I am sure HONDA guys make sure our car handles great with stock package. But, it will handles much better larger tires and wheels.


[Edited by Stealthy_S2K on 05-29-2001 at 09:27 PM]

 

Well, you have to consider that an F1 car has about 1 inch of compression travel, if that. The tire itself deforms about 1 inch so it accounts for a full 50% of the suspension travel on an F1 car.

The reason that F1 cars and Indy cars have such minimal suspension movements is due to the fact that they are very aerodynamically sensitive due to their ground force packages. A long travel suspension adversely affects the handling of these cars due to a variety of reasons that I will forego explaining for brevity.

It is far easier and more accurate to tune a mechanical spring/shock combination than it is to tune suspension compliance by a tire's structural composition and air pressure. In fact, a tire's air pressure is not static, depending on many factors, including ambient temperature, and load conditions that cause the air to heat up. This does not allow consistent damping results.

Finally, a tire acts essentially as an undamped spring. Drop one on the ground and it bounces. There is no damper to absorb a tire's energy other than the construction of the carcass itself.

Therefore, one can view this similar to why you would want a stiff chassis instead of a flexible one. By isolating suspension movements to only the spring/damper combination it is much easier to tune the car to the desired level of handling.

Notice that on GT cars, touring cars and rallye cars set up for a road course, the wheels are considerably bigger and the sidewalls are considerably smaller and stiffer for this very reason.

 

And also don't forget that while Honda made a sports car, they had to make a happy medium for road worthiness vs. extreme sport. With in reason, lower profile tires can be a benifit. Assuming that's what your going for.

 

[QUOTE]Originally posted by s2kblk
[B]I just did it for looks, so it may or may not have hindered performance.

 

Race cars use nitrogen in their tires which is more consistant than air.

Obviously there is SOME need for the air spring effect of air filled tires otherwise the ultimate end to the low profile trend would be a solid rubber tread wrapped around a wheel (like on a land speed record car).

While I agree with all the points made above there IS a need for some tire compliance. Using a compliant tire allows the suspension to be stiff while still retaining the ability to absorb some bumps in turns without causing the car to skip out sideways because of them. A stiff suspension can not track small road irregularities due to high spring rates and shock rates. There is a "minimum" force necessary to move the suspension. A compliant tire deals with the forces below this minimum.

 

Formula 1 cars have tall sidewalls mainly because the rules limit their wheel diameter. Ever see a super tourer? They are 2L "touring cars" (sedans) as raced in Europe. There was a short lived US series too. They have the most extreme low profile tyres you've ever seen, literally 25 section or lower. That's not to say that it's the right thing for the street. On the roads where I live I would be willing to bet any lower than stock on the S2000 would slow you down.

One thing that I wonder about regarding F1 is also heat dissipation. You can make a softer, stickier tyre if you can stop it from melting. If you have a tall tyre with steel belts it will conduct heat very well and dissipate it from the entire carcass surface area. If you make it low profile the heat has to escape via the bead into your rims - which I think would be less efficient. Just a thought.

On Honda tuning the S2000 suspension to use sidewall flex, I think you're almost certainly right. It definitely feels that way on the less than perfect backroads where I drive my S. Until we have fully active electronic suspension it's going to be very hard for car makers to tune the suspension compliance versus frequency and amplitude in the way they really need to. Tyres are an important part of that equation right now as you pointed out.

[Edited by naishou on 05-29-2001 at 09:55 PM]

 

Race tires have about 1/4 inch (if that) of tread so they can dissipate heat.

While I can see low profile tires on the track which is a much smoother surface than the street, real world pavement is not the optimum enviornment for them.