All about steering angles, and what they mean

[zekew64]

I'm writing this because I've seen many people have steering complaints, about their trucks not driving correctly, or having questions relating to either lifted or lowered trucks.

To begin with, every vehicle has three angles in the front. Some vehicles, namely front-wheel drive vehicles, have these same alignment angles in the back, but we won't worry about those.

The three main angles are as follows (I will also provide an explanation to what each means in terms of tire wear and steering):

1. Caster angle
2. Camber angle
3. Toe-in/toe-out

Explanations of each:

Caster angle: This angle how far forward or rearward your front wheels sit in the wheel well. Negative caster, with the wheels towards the rear of the truck, will result in excessive steering effort, as well as slow steering return (the rate at which your steering wheel returns the truck to the straight position after making a turn). Positive caster--with the front wheel towards the front of the wheel well, on the other hand, will result in seemingly tight steering (where it seems it takes too much effort to turn the steering wheel), and slow steering wheel returnability. Negative caster angle can also cause "steering kickback," which is where the truck strikes a bump in the road and the steering wheel gets jerked out of your hand and you have to correct the change in direction. A vehicle will also pull in the direction that has the least amount of positive caster angle as well. (Note: Caster angle has little or no effect on tire wear.) The way to think of caster angle is like this: Look at the front of a bicycle. Most bicycles have positive caster angle designed in, because positive caster allows the rider to have a feel for the road, and positive caster angle also promotes good directional stability. However, too much positive caster angle will give the rider a harsh ride (where the force felt is more than the force absorbed).

Camber Angle: Camber angle is how much your tires tilt in or out at the top of the tire. The most obvious way to tell what your camber angle is, is if you have tire wear on either shoulder (edge) of the tire, with little or no wear in the middle of the tire. Negative camber shows as tire wear on the inside edge of the tire, as well as pulling in the direction of the lean. Positive camber shows as tire wear on the outer edge of the tire. Pulling can be caused by too much either positive or negative camber; however, most vehicles have some negative camber on the passenger side of the vehicle, with some positive camber on the driver side. This is to offset road crown, and most measurements are between 0 degrees and 0.5 degrees either way.

Toe-in/toe-out: This is where your front wheels are slightly pointed in or out at the front edge. How to determine this is to make two measurements, from the same point on both sides of the tire. The difference is how much in or out the toe setting is. Measure the front edge and subtract it from the back edge. If the result is positive, you have toe-out. If the answer is negative, you have toe-in. Toe-in adjustments are made with the tie-rod, either the sleeve (as in a conventional or steering linkage system) or with the inner tie-rod (rack and pinion steering). Pretty simply, loosen the adjustment and you get toe-out, tighten it and you get toe-in. Excessive toe, in either direction can cause feathering of the tires (looks like the whole rib on a tire is being slid sideways) or pulling. A truck will pull towards the side with the least negative toe (toe-in) or the most positive (toe-out).

In terms of lowering or lifting a truck, remember: You need to keep your alignment angles as close to stock as you can get. If you don't, you will have one, or many, of the problems I've listed above if your steering angles aren't correct. And we all want to save money by not having to prematurely replace tires, correct?

HOWEVER, due to the nature of the fine tuning that must be done, leave adjustments to a shop to do--it is money well spent, and you won't ever have to deal with the guesswork involved in doing it yourself; believe me, I've dealt with this on my own more than once, and it is a PITA.

----------

If someone could, I would like this to be stickied, so that people can find it if they have questions about their alignment or steering questions.

[Muscleford]

Good info.

I have been told that too much negative caster will also make the car darty, quick response to turns of the steering wheel and hard to drive.

[zekew64]

Originally Posted by Muscleford

Good info.

I have been told that too much negative caster will also make the car darty, quick response to turns of the steering wheel and hard to drive.

Before I correct this, I will say that I have had some confusion with this, and don't want to pass on bad information. As my steering/suspension final is coming up, I now have these angles down, in terms of knowing what they are and how a vehicle can have bad characteristics when the vehicle is not aligned properly.

But, you would be correct. Negative caster will also cause high-speed wheel shimmy, with the vibrations transferred straight up to the steering wheel. Just last night, I adjusted my suspension from a negative caster to a positive one, and what a difference it made. Needless to say, the shimmy I was dealing with is gone, as well as the truck rides better due to the suspension absorbing more shocks instead of transferring those shocks to the cab.

Again, I apologize if I thought that you were incorrect in your statement; turns out I was the one who was wrong. And I am man enough to admit when I am wrong, as I wish that everyone could have a decent ride from a properly-aligned suspension.