Caster, Camber, Tow-In – Wheel Alignment
AutoWhat is Caster – Camber – Tow-in – Wheel Alignment
First, for those of you who don’t understand caster, camber, and tow-in, let me explain. Caster is how the wheel sits in relation to a vertical kingpin or ball joints. It can be vertical true or -or-degree, positive or negative. Example: the front wheel of a bicycle has positive caster. Note that the wheel extends forward from the axis of rotation. Thus, it allows the steering to return straight when you take your hands off the handlebars. A positive caster vehicle will do the same. This adjustment is for handling or riding and requires a camber gauge for adjustment as well as certain hand wrenches.
Camber denotes the position of the wheel relative to the vehicle, such as in at the top and out at the bottom (negative), or outside at the top and in at the bottom (positive). The recommended setting can be from negative 1 to positive 1, with -0 degrees straight up and down, or true vertical. If it is extreme in one way or another it will cause wear on the inner or outer edge of the tire and possible scallops may appear. This adjustment is for tire wear and possibly some handling, also certain tools like the upper control arm wrench and a Tomcat camber adjustment tool can be helpful.
After the caster and camber are adjusted, we move on to trailering, which is also for tire wear and again, possibly some handling. Tow-in is the ratio of the left front wheel to the right front wheel. If the front wheel tires point slightly toward each other, that’s towing. If they’re far from each other, that’s towing. Before this adjustment is carried out, the center of direction must be made. This is the relationship of the steering wheel to the left front wheel. With the steering wheel positioned straight (centered), align the left towed wheel slightly in or about 3/16 in. This can be done with the use of a string wrapped around the left rear wheel and pulled forward using the rear wheel as a guide to get a straight line to the left front wheel, thus allowing the string to indicate the position of the left. front wheel being towed or towed. The left wheel must be adjusted first and the right foot. wheel adjusted to the left wheel to obtain a toe-in of about 1/4 in. There are trailer adjusting tools such as a trailer adjusting bar, a tie rod spacer, and a tie rod kit that can help achieve this alignment.
There are times when a shim or adjustment to move the rear of the control arm out will give the wheel the proper setup if one understands what that move will do for both setups (caster and camber) simultaneously. That knowledge or understanding plus the proper hand tools and some experience is all it really takes. Well, maybe a good trainer would come in handy. However, going back to the move made by adding a single shim to the rear of the upper control arm (shims vary in thickness by the way) would give a less negative trailing angle and more positive camber. I hope this helps! Any questions? lem boyd
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