I think I better understand what you're saying, but that's not the way it works. I'm trying to figure out a way to explain it...someone else want to have a go?

 

Okay. I had to go to wikipedia because I was finding it hard to put into words. It's something I understand, but can't explain...like why water is wet.

"The tendency of a car to oversteer is affected by several factors such as mechanical traction, aerodynamics and suspension, and driver control, and may be applicable at any level of lateral acceleration. Generally, oversteer is the condition when the slip angle of the rear tires exceeds that of the front tires, even when they are both small."

Given your extreme example of a 20" wide tire in the front. If you are turning, your rear tires will obviously exceed that of the front tires. Even when the slip angle of your front tires is 0, your rear tires may be at .00001, meaning the rear end is traveling laterally more than the front = oversteer.

 

I agree with everything posted, but i dont see how it disproves my idea. I think it actually reinforces what I was saying.

basically if a car has a greater slip angle in the front it will understeer. If there is a greater slip angle in the back it will oversteer.

http://en.wikipedia.org/wiki/Slip_angle


What I am talking about is when you reach a point that the front tire has so much grip there is 0 slip angle it wont matter if you put an even wider tire on it because the wider tire will have 0 slip angle also. Even though the wider tire does have more grip you will never be able to make use of it because the maximum grip of the smaller tire was never exceeded.

Either front tire would have a slip angle of 0. Thus the only way to change the ratio of front to rear slip angles would be changing is the slip angle of the rear tire.

This is just theory. I dont know if it possible in real life to have a tire with a true 0 deg slip angle. In reality the front tires would probably have a slip angle very close to 0, but i would argue that those angles would be so small that we could just consider them 0.

does that make sense?

 

No.

Let's say you put a car on train track rails. And let's say that the front wheels are like train wheels in that they will never go off track. And let's say your rear wheels are flat with no lip on them to keep them on the track. If you turn, the front wheels will stay on, but the rears probably won't.

 

exactly. so if we pretend the front wheels are on tracks because either size would never lose grip the only way to change oversteer/understeer is to change the size of the rear tire. (assuming alignment/suspension is the same)

so in real life a 225 front that is not slipping (0 slip angle) and a 255 front with 0 slip angle should cause no more and no less oversteer if the rear tire remains the same. In both cases the front is on rails and the only way to change the oversteer characteristics is to increase or decrease the slip in the rear.

Disclaimer: ^this is all assuming that there is no slip angle in the 225. just because i cant feel it does not mean its not slipping some.

 

Okay. I think I was being thrown off by your assumption that a car has the ability to not slip under normal driving conditions. A tire must slip to generate any sort of force. (do not confuse tire slip with sliding). Maybe this discussion will help: http://www.f1technical.net/forum/vie...php?f=6&t=6300

I think what you're trying to say is that if you've never experienced oversteer in a car, and you add more front tire, you will only continue to not experience oversteer. This is, in general, true. However, this would involve driving incredibly slow so that when turning, your rear tires follow the exact same path as the front tires. What makes a car able to turn sharply is the rear traveling more than the front. This travel will be quicker if there is (relatively) less traction for your rear tires.

So what I'm saying is that with a 255 Front / 255 rear setup on an s2000, your rear will want to come out more easily than with a 215 front / 255 rear setup. You, however, may not be turning at a rate of speed where it is noticeable, but it will be a characteristic of the vehicle. Even with a 275 r-compound tire all around, you would still be able to make even an s2000 slip to a noticeable degree.

 

Thats not what im trying to say at all. I do appreciate you trying to help me though. I will try to explain it in a slightly different way.


With my current set up (stretched 225 in front and 255 in back) when i go into a corner to fast the front tires do not lose grip. They stay firmly planted to the road. At a certain point the rears will lose grip and the tail will slide. In this situation oversteer happens when the rears exceed their max grip. The front tires are never exceeding their max grip and are always staying planted. When the rears let go is what decides when the car starts to oversteer.

now lets assume I kept the same rear tires and put 255 tires on the front as well. Now lets assume i took the same corner at the same speed as mentioned above. Again the front tires would not lose grip and stay planted throughout the turn. The rear tires would lose grip and the car would oversteer at the exact same point they did in the previous example.

In both example the 225 in front and the 255 in front are NOT exceeding their max grip. They are both providing the exact same amount of grip in the front. It is the rear tires that are slipping and since in both examples the rear tires are the same they will lose traction at the exact same time.

In these examples the change of front tires will not make the car oversteer any more or any less.


Also, Happy Turkey Day!!!!!

 

IMO this is not so, cornering is a dynamic process and changing one parameter will result in a change (perhaps small, but still present) of the car's overall balance. Increasing grip in front via the wider tire but keeping everything else the same (rear tire, corner entry speed, entry point, steering input etc) will result in the front taking a smaller turn radius. The rear turn radius may not change (it probably actually does due to the faster weight transfer) but result will be a higher amount of yaw which is increased oversteer.

Maybe some of you physics gurus will comment after digesting your turkey.

 

it's all about balance..

let's say you have a s2000 with 225 front and 245 rears... and it has very neutral handling. by making the front tires wider and thus gripping more you have upset the balance. now instead of that neutral balance, you've made the front have more grip... it will have a higher tendency to oversteer now.

 

I am having some issues following some of the "theorys" flying around. Bottom line is a wider/tire with more traction in the front (keeping the rears the same) WILL result in more oversteer. Just like a narrow/tire with less grip WILL result in more understeer.

It is difficult to use the perspective that if you have tire x in the front and y in the rear and y is the limiting factor in the equation and you change to tire z in the front and keep y in the rear that the handling characteristics will not change. They will because there is no car (atleast not a driveable car) that purely exhibits oversteer or understeer characteristics 100% of the time. There are tons of variables that determine how the car will respond to the set of variables, sometimes leading to oversteer/somtimes understeer. With tire z you will be more likely to oversteer at times when the car may have felt neutral. The wider front tires will also change the "turn in" characteristic of the car.