Ackermann steering geometry

[L_O_O_M]

Hi all

I was wondering if all cars use Ackermann steering geometry these days?And what are the pro's and con's?

[Bryce]

Ackermann is necessary. It means the inside wheel turns tighter than the outside wheel. If you draw two concentric circles with different radii you would want the inside tires (front and rear) tangent to the smaller radius and the outside tires tangent to the larger radius. This would be an example of perfect ackermann at one turning radius, now the trick is making close to perfect at all turning angle. Anything not perfect would result in loss of traction due to srcub.

If you hear some of those SUVs with larger diameter and wider wheels slowly driving/turning through parking lots and the tires are squeling, thats an example of not perfect ackermann.

[MIKE67]

Bryce, a first time for everything. But, I have to disagree with your first sentence. I agree with everthing else. Look at off road racers (since the chassis is raised you can easily see the ackerman), some are running ackerman, some anti and some pro-ackerman. It probably doesn't matter what the inside tire is doing since they are running in loose gravel and rocks.
Some dirt track guys think pro-ackerman helps them turn. Because the outside tire is more heavily loaded it controls where the car is going and the inside tire scrubbing creates an off-center force which helps rotate the car.
The other view is on high speed turns on asphalt. Ackerman is really a variable toe-out (the inside tire is turning tighter than the outside, so it is actually toeing out). In a high speed turn the tires are generating a significant slip angle (the only way to generate a lateral force). This slip angle effectively creates toe out at the inside tire, since the outside tire contact patch is turned less than the centerline of the wheel. And again the outside is controling the direction of the car. Therefore you may want parallel steer or even some anti-ackerman so that the inside tire isn't being scrubbed at speed.
I am still learning. Just when you think you have a handle on something, you learn something else and you have to realign all the theories. This was the case for me and my understanding of ackerman.

[Rod]

Page on ackerman click here

[David Pozzi]

I tried it on my 67 Camaro back around 1976! The car was next to impossible to push if the wheels were turned. Hard to tell much difference in an autocross at that time, I wasn't very experienced. My hunch is to run some Ackerman, not Anti. I asked Guldstrand back then and didn't get a definite answer.
David

[killer69]

I tried it on my 67 Camaro back around 1976! The car was next to impossible to push if the wheels were turned. Hard to tell much difference in an autocross at that time, I wasn't very experienced. My hunch is to run some Ackerman, not Anti. I asked Guldstrand back then and didn't get a definite answer.
David

What would HE know anyway???? honestly

[ace_xp2]

Carroll Smith found in later books found beyond one hundred percent pro Ackermann to be beneficial in every circumstance, the direct quote is out there somewhere, but here's a reference to it at least:
http://www.sccaforums.com/forums/for...97/scope/posts
If I recall right, he went to the 150 or 200 percent range in his testing and didn't find anything but gains.