What is "Ackerman Geometery"?

Something to do with steering, I see, but I can't find any explanations. All anyone says is that it better be correct or you're going on a ditch tour.

[Eric Coffey]

Read this thread:

Formula1 Steering Question.

Strange, I did a search first so as not to load up the server with duplicate threads...but nothing came up.

Anyway, now I know. Thanks!

[Tyson Schmidt]

Toe- in causes understeer, and makes the car less darty. Toe-out improves turn-in response. Toe-out on turns is designed into most cars because the inside wheel has to travel a tighter radius than the outside wheel.

Then there's the 911. Noe toe out on turns. Why? To reduce the dartiness inherent in a rear engined car. Our cars have all kinds of understeer inducing tricks built onto them to make the cars more suitable for the masses. (Who generally don't know how to drive.)

The lack of toe-out on turns is achieved by placing the steering rack ahead of the centerline of the outer tie-rod ends attachment point to the knuckle. (On cars with the rack behind the front axles centerline only.) As the steering turns, the tie-rods straighten out slightly, effectively making them longer. Longer tie-rods on a rear steer car means toe-in, which compensates for the natural tendency for toe-out on turns.

If the steering rack were in direct line with the outer tie-rod ends, steering the car would make the tie-rods arc forward from center, effectively making them shorter and causing toe-out. This is actually a good thing, and would reduce the 911's low speed understeer problem. That's why Autocrossers set their cars up with toe-out to reduce low speed understeer.

I hope this all makes sense. I know it's hard to visualize, but I can't very well draw pictures to better explain it.

Cheers!