Brian T

What the title says...visuals usually help me understand better. From what I understand, basically the tire starts to point in a different direction than the wheel and it is measured in degrees. When you reach a certain slip angle depending on the tire, you are maximizing the tires traction. But how are the tires pointing in a different direction? Is it bending?

mpg9999

Imagine you tire is pointed straight forward like this | and imagine your car is moving completely sideways like this _ That would be a 90 degree slip angle. Its really simple once you get it. The tires/car is just pointing in a different direction then the car is traveling. Slip angle is the difference between the direction your tire is pointed and the direction your actually traveling.

mpg9999

Well I just did a google search and apparently I am wrong. Its actually "The angular difference between the direction the contact is pointing and that of the wheel itself is called its slip angle." This is because tires are flexable and the contact patch flexes.

mpg9999

ok, I just went and looked at "secrets of solo racing" by Henry A. Watts and he describes it like I did in my first post.

So, one definitions is measuring how much the tire is sliding, and the other one is measuring how much the actual contact patch is flexing relative to the direction the wheel is pointed. Im interested in getting a good answer to this.

Egz

Egz

5.0 RACER

Ah. Fred Puhn's book, "How to make your car handle".

Egz

I've got that book. Helpful, just wish there was a little more FWD content.

roadRacer

It is really very complicated and simple at the same time.

It is a combination of all of those things. When you are turning, tires are not round. There is lots of deflections and lots of slipping. Tire engineers work and work at optimizing all of this stuff to make the car go as quickly as posible around a corner. To us simple people we have to think of it as the total. If we are cornering and the rim is pointed some direction. Between the tread deflection and the amount the tire is just slipping from the side loads, is the total slip angle.

Given some certain load, and some radius corner, and rim width, and air preassure (and a differance from front to rear) there is a slip angle that gives maximum cornering. We can make slight adjustments with air preassure. We can make more changes with rims widths, we can also improve weight transfer and change the ideal slip angles (did I mention that it is different between the inside tire and the outside tire because of weight transfer and the actual differance in how far the tire is traveling in the corner, the ideal for teh car beomes the average of the ionside and outside slip angles).... There are a few other things that make this even more complicated....

So what does all of this mean? All we can do about this is choose between the available tires we have to chose from and do some other basic things we have all been told makes our car corner better. If you decide to become a tire engineer and happen to get involved in race tire development you will get to know all of these things and much much more, intimately, but to us mere mortals it is something nice to know the theory about, but it is little more than a mental exercise. There is just nothing we can really do about it.