Alignment settings

[billd]

Does anyone have any advice on alignment settings for autocross? I'm thinking of

Front - 2.0 deg camber, 0 inches toe
Rear -2.5 deg camber, 1/16 inches toe in

The car has 180# rear springs, 21mm front torsion bars, stock front and rear sway bars, and Koni adjustables all around. This is on an otherwise stock 73 2.0L.

Will the rear toe-in help grip accelerating out of turns or am I better off with zero toe front and rear.

[Dave at Pelican Parts]

Rear toe-in will help to keep the rear of the car behind you. Toe-out, like you get when the suspension compresses, will make the car try to rotate more on you. To keep the toe angle closer to zero or toe-in when the car is accelerating out of a corner, you want a little toe-in.

The overall feeling will turn out as: Toe-in will make the car stable. Toe-out will make the car twitchy. If the back end of the car is twitchy, it will be a lot easier to spin.

I would put a little toe-out in the front--if the front end is twitchy, it will help the initial turn-in. I would keep a little rear toe-in, so you can keep the tail behind you.

i have experimented with rear toe-out, and the back end of the car really wanted to steer the rest of the car while under power in a turn. It worked OK for autoX, but I really hated it on the street and on the Big Track. I find myself more confident in the car and able to push it harder when the back isn't trying to pass the front so much...

--DD

[billd]

Thanks Dave, what do you recommend for camber?

[nine_one_4]

Originally posted by Dave at Pelican Parts
Rear toe-in will help to keep the rear of the car behind you. Toe-out, like you get when the suspension compresses, will make the car try to rotate more on you. --DD

I think you get toe-in when a semi-trailing arm suspension compresses. Check out my pictures here and the information on this page. The pictures of the wheel's plane in my post are of the right rear suspension when viewed from behind and to the right of the car.

[Dave at Pelican Parts]

Hmm... You should gain toe-in under acceleration, as well. The wheels will be pushing forward against the pivot, which should toe them in.

OK, then--why is static toe-in preferred? Perhaps because tires with zero toe the tires tend to wander, while with toe-in they tend to stay toed-in and going straight ahead.

Not sure. But I do know the results when I tried toe-out in the rear; it was not a very good feeling and I was much happier and better able to push the car when I went back to rear toe-in.

--DD

[nine_one_4]

I think you were right except for your statement that with a semi-trailing arm you get toe-out on compression. Because of the geometry you actually get toe-in on compression. Here's some interesting information I found on Porsche's "Weissach axle".


In the mid-70s, Porsche developed this unique rear suspension for its award-winning 928. Basically it is a variant of semi-trailing arm suspension.

In any suspensions, the pivot joints must be inserted with rubber bushing to absorb noise and vibration. For conventional semi-trailing arm suspension (first row in the following picture), whenever under braking, the momentum of the car body tries to pull the car "away" from the rear suspension. Due to the elasticity of the rubber bushing, the rear wheel will toe-out. As a result, the car will oversteer.

Weissach axle was designed to eliminate this oversteer (second row in the picture). By splitting one trailing link into two pieces, with a pivot joint added between them, the oversteer under braking can be elinimated or even introduce some understeer ! This help stablizing the cornering motion. Some people call it as "passive rear-wheel steering".