Question..

[V6Bob]

There are different kinds of "bind".

When the car rolls, the lcas are not quite square to the brackets. This is not desired, but it's unavoidable. Poly bushings can bind in that situation, and rod ends, which can pivot, fix that.

Anti-squat works by deliberately using the acceleration force to lock the suspension, so the car won't squat. Rod ends do little to reduce that kind of bind. In a drag racing car, particularly with soft and low pressure rear tires, you can use a whole lot of antisquat, but if you're trying to corner on street tires while accelerating, too much antisquat becomes a bad thing, because the locked up rear suspension won't handle the corner well.

[hou-tex-six]

<blockquote>quote:</font><hr>Originally posted by V6Bob:
There are different kinds of "bind".
if you're trying to corner on street tires while accelerating, too much antisquat becomes a bad thing, because the locked up rear suspension won't handle the corner well.<hr></blockquote>

ehh, a little more lively on the turns, no problem, just learn to countersteer and you'll be fine.

Cp

[John_D.]

Here's a visual for you. Lay a book down on your desk, about 12" away from you. Now lay an unsharpened pencil (or something similar) lengthwise between you and the book. Let's say the eraser end toward you. Pencil touching the book

----
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----
.
.
.
.
xxx

Dashes are the book, dots are the pencil, xxx is you. Now push the pencil toward the book. So far so good... The book is your car. The pencil is your lca. You are the differential.

Alright, now, lift up the eraser end of the pencil about an inch. Try to push the book again. But here's the catch... You can't push down on the pencil at all, only straight ahead. Your end of the pencil is trying to raise up.

That's what happens when the car is lowered. When you take off, the differential tries to rise up into the wheelwells. At the instant you take off, you actually have less weight on the tires, because they are trying to lift. The car ends up squatting, and everyone says, ohhh, look at that weight transfer!!! Uh, no.

Ok, here's the opposite situation. Imagine that you could lower the eraser end of the pencil. (or even get the book to the edge of the desk and actually lower your end of the pencil). Now when you try to push the book forward, your end of the pencil is going to also be pushed downward. That's your tire planting on initial take off. And the rear of the car may actually lift. Possible problem - if there is too much lift, you end up transferring weight to the front of the car. Which is bad for traction once you start rolling but are still in that first 60 feet.

Best situation is to have that pencil perfectly level. Or maybe have your end down just a teeny little bit... For straight line traction anyway.


There's a whole different theory on cornering and roll center, where it's better to have your end of the pencil higher after all, but I can't explain that one...

[V6Bob]

John D. - great explanation. I agree with everything except:

"Best situation is to have that pencil perfectly level. Or maybe have your end down just a teeny little bit... For straight line traction anyway."

If you start with the pencil level and accelerate, the back end of the car starts to go down, your pencil is no longer level, and it keeps going down. That's squat.

As you angle the pencil just a bit when the car is not moving, under acceleration the rear end of the car starts to be pushed in the up direction and the car squats less. When the angle reaches a certain point the car stays level under maximum acceleration. Thats "100% anti-squat".

My understanding is that road race cars and some high performance sports cars have some antisquat (25%???) dialed in. They stop there because of the bind and because, as you said, the roll center effects start to hurt cornering.

OTOH, many pure drag race cars use close to 100% antisquat or even a bit more. As you say, this can cause the rear of the car to lift a bit, but the weight transfer due to this is small. On a street car, the bind would be very noticeable (and bad) at 100%.