Ok so I understand what the "anti" effects do and how to calculate them in a suspension but how do you know how much to run? Is this just something that comes from experience or is there some way to figure out how much you need?
Ok so I understand what the "anti" effects do and how to calculate them in a suspension but how do you know how much to run? Is this just something that comes from experience or is there some way to figure out how much you need?
Good question. Anti dive in the front comes from having the front control arm pivots further apart than the rear as measured vertically.
Anti squat is on the rear, but in that case the front pivots are closer together than the rear on an IRS. Of course that only really works with RWD cars since it's a function of acceleration. With a solid (tube or 'stick' axle) It's possible to get over 100% anti squat in the rear by moving the suspension link front pivot points.
As far as figuring how much you need, I'm in the dark too. I'm sure there's an answer in that big expensive SAE book that I'm going to buy when I win the lottery.
Cut and pasted from another site.
"As roads became better auto engineers in the late 30's to the 50's were concerned with the "ride" of the family car. To do this coil springs with softer and softer rates became the norm. While softer springs and airplane shocks improved the "ride" stopping and cornering became hindered. To solve these problems anti-roll bars for cornering and anti-dive for stopping became the problem solvers. Anti-dive has to do with the angles of the control arms looking at the side view. The torque of the wheels on the suspension through the control arms act like a stiff spring when the brakes are applied. If you google anti-dive you can look up the article that was posted on Circle Track's w e b s i t e "
Smith discusses it some in one of his books. Don't recall which one. If I remember, 2 or 3 degrees was about the starting point.
Dr. Hess wrote: Smith discusses it some in one of his books. Don't recall which one. If I remember, 2 or 3 degrees was about the starting point.
Something about that doesn't sound right... I've always heard antis expressed in percent, not angle.
Also, anti-squat is a RWD thing, if my assumption is correct and this is for a Civic, you want to look at anti-lift.
ReverendDexter wrote: Also, anti-squat is a RWD thing, if my assumption is correct and this is for a Civic, you want to look at anti-lift.
Yes, for FWD (or grip-challenged front wheels on AWD), it's anti-lift.
There are anti-lift kits for Subaru WRXs (at least the early ones), apparently due to poor geometry. (Whiteline makes them: Whiteline Anti-lift White Paper (PDF)) The kit increases grip during corner-exit acceleration. On Saab 900 rally cars, the lower control arm mounts/bushings, which are asymmetrical, are swapped from one side of the car to the other, in a criss-cross manner, which is said to make the car accelerate a lot better (at the expense of ride quality).
How much is too much? Who knows, but at some point you're going to get binding...
ReverendDexter wrote:Dr. Hess wrote: Smith discusses it some in one of his books. Don't recall which one. If I remember, 2 or 3 degrees was about the starting point.Something about that doesn't sound right... I've always heard antis expressed in percent, not angle. Also, anti-squat is a RWD thing, if my assumption is correct and this is for a Civic, you want to look at anti-lift.
No this is for a Formula SAE car.
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