Originally posted by miata13B
I would have to totally disagree with that statement. It is called an Ackerman's toe where the front toe is negative and the rear toe is positive. Think about the psychics invovled. As the outside wheel gets the weight transfer, pointing outward of the car where as the front is pointing inwards will create a semi circle making for more traction throughout the turn and more stability. Try using it on your FF cars and tell me what you think.
Actually,
m13B, I have to to disagree with you. From my experience, that is exactly backwards. To answer the question, negative is TOE OUT, and positive is TOE IN, at both ends of the car. So typically you want to run +0.5(IN, front)/-0.5(OUT, rear) for a baseline toe adjustment for an understeering car. Also, what you describe is not Ackerman Toe - read a little down and I'll explain what Ackerman is.
In general, you want the outside tires to be biased in the direction you are turning, because they are more heavily loaded during a turn, and thus are bearing most of the car's weight. The unloaded inside tires aren't doing much, so it isn't efficient to bias the alignment in their favor. This means the ideal setup is a small amount of toe in at the front, and a small amount of toe out at the rear. You got this right in theory; you just have the values reversed.
Toe OUT means the more heavily loaded rear wheel is helping the car rotate through the turn; toe in keeps the rear tucked in tighter, promoting understeer. You hardly ever want to run toe in at the back, unless the car is very unstable. If that's the case, something else is wrong anyway - you should be lookng at springs or damper settings more closely, or back off the rear swaybar.
Ideally you want toe IN at the front, again so that the more heavily loaded tire is biased in the direction you want to go. Front suspension geometry is designed with something called
Ackerman Toe, meaning that toe out increases dynamically as steering input increases. This is done so that the as you steer more sharply, the inside front tire steers to a tighter-radius track than the outer tire, allowing it to take the inside line without scrubbing. If you set the car up with static toe out in front, the Ackerman effect means you have too much toe out during corners, making the inside tire scrub.
Toe out also tends to make the car twitchy and tend to wander. In front, this twitchiness can help some by making turn-in seem a little crisper, but in the long run, I don't think it helps. Some people, particularly autocrossers, like to run toe out in front - but in autocross, the car is rarely settled for as long as it is on a road course, and so what you're giving up in steady-state cornereing and straights may be helped under moer dynamic conditions. At any rate, it runs contrary to the engineering physics behind alignment settings, so I don't like to do it. However, the rear of the car is following the front down straights, so the wandering tendency caused by the rear toe out is reduced in effect. This is why I tend to start with half a degree of toe out in the rear and zero toe in front, only moving to the front if additional adjustment is required.
Originally re-posted by Famine:
Camber is the vertical angle of the tyre. Negative camber - where the top of the wheel is further away from the car than the bottom of the wheel is incredibly stupid, and only ever seen when you've crashed a car (in real-life, that is). The more positive you set the camber, the better the car handles during a corner - but too high camber will give your brakes problems. Higher rear camber than front is rarely a good idea, as it will make the car understeer more.
Again, also right in theory, but wrong in values - he's actually talking about POSITIVE camber in this post. Let me throw in my standard repeat that PD got the camber values wrong. The camber they are referring to in the tuning screen is actually negative camber. There's no reason you'd ever put positive camber on a performance car, ever. On a London Taxi, yes, because it can help reduce the turning radius; but never on something driven for handling.
Hope this helps!
