What is the relationship between tire physics and slip angle?

[fog37]

Hello everyone,

Does anyone know what the slip angle is in relation to rubber tires? What is its effect? Is it a positive or negative effect?

My basic understanding is that when a tire is cornering, the tire does not point directly along the curved direction of motion but is slightly twisted, since it is made of rubber, and points slightly towards the outside of the curve...

 

[sophiecentaur]

Have you Googled "Tyre Slip Angle" yet".

 

[FactChecker]

Hello everyone,

Does anyone know what the slip angle is in relation to rubber tires? What is its effect? Is it a positive or negative effect?

My basic understanding is that when a tire is cornering, the tire does not point directly along the curved direction of motion but is slightly twisted, since it is made of rubber, and points slightly towards the outside of the curve...

The tire points inward. The tread distorts as the wheel rolls. The tire must point further in the desired turn direction than the vehicle will actually turn.

 

[Ranger Mike]

Does anyone know what the slip angle is in relation to rubber tires?
yes

What is its effect?
could be good until it goes to bad

Is it a positive or negative effect?
positive until it goes to negativeMy basic understanding is that when a tire is cornering, the tire does not point directly along the curved direction of motion but is slightly twisted, since it is made of rubber, and points slightly towards the outside of the curve...

on a motorcycle? which tire?
on a race car are you talking about the right front in a left turn corner or the left front tire in a left turn?
Or are you talking about the rear tires?

i suggest you read race car suspension class ...above...see page 4 post #62
page 12 post # 228
page 24 post # 470 lumpy and the down force
page 41 post # 811 centrifugal vs centripital

 

[FactChecker]

The slip angle is the difference between the direction that a tire is pointing and the direction that it is moving. My experience with it was in simulations that only had to be believable, not necessarily accurate. We modeled it as a lateral (versus tire point direction) force that was a linear function of the slip angle. When the tire points more to the left, the force is to the left.
I assume that a real analysis of turning force would require detailed understanding of the tread design and pattern. It seems that a tire company could more easily set up experimental fixtures than rely on analysis, but I have no authoritative knowledge of that.

 

[sophiecentaur]

I read an ancient book -The Sportscar by Colin Chapman. He explained the relevance of slip angle. When a car is cornering, both front and rear wheels have a slip angle. If the front wheel slip angle is greater than the rear wheel slip angle then you have to steer harder into a corner to go where you want. This is called Understeer and is the safest arrangement but, of course, it reduces the cornering ability - not good for racing and being flash. A 'manoeuvrable' car will have neutral or even Oversteer and the rear wheels will slip more, allowing the back of the car to hang out and, eventually spin. This accounts for the trick which rally drivers use when they use 'reverse lock on the way round a bend fast.
The slip angle is affected, not surprisingly, when power is applied to a wheel; a rear wheel drive car tends to oversteer (we've all been there) and a FWD car tends to understeer, which is more comfortable for the nerves of the passenger.
PS A google search will yield masses of interesting facts about this.

 

[Baluncore]

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

 

[cosmik debris]

This article from Michelin explains a lot about tyre performance.

http://www.dimnp.unipi.it/guiggiani-m/Michelin_Tire_Grip.pdf

Cheers

 

[fog37]

Thanks everyone. All very useful.

I appreciate the Michelin article from cosmik debris. Learning a lot.