Originally Posted by jleon01
Front Axle Toe
L: Initial: -1/32" Final: 0"
R: Initial: +1/8" Final: +1/32"
Total: Initial: +3/32" Final: +1/32"
Front Axle Camber
L: Initial: 0deg Final: +1/4 deg
R: Initial: +1/8deg Final: +1/4deg
Side to Side: Initial -1/8deg Final: 0deg
Rear Axle Toe
L: Initial: +1/32" Final: 0"
R: Initial: +1/32" Final: 0"
Total: Initial: +1/16" Final 0"
Read Axle Camber
L: Initial: -1/2deg Final: -1/4deg
R: Initial: -7/8deg Final: -1/4deg
Side to Side: Initial: 0deg, Final: 0 deg
Camber is the tilting IN or OUT of the top of the tire from vertical. Tilting in is negative camber, tilting out is positive camber. Excessive camber, either way, will cause one side of the tire to wear, ALL around. Not just one spot. That is easy to understand as the tire is constantly applying more weight on a side rather that all across the tire tread.
Toe-In or toe-out, is the pointing in or out of the front of the tires. If a person is pigeon toed, they have excessive toe-in. Again, excessive toe-in or toe-out will also cause tire wear. This wear shows up as a scuffing across the tread of the tire. This wear shows up all around your tire, not just one spot.
Caster is the third level of steering geometry on vehicles and is responsible to keep the vehicle traveling in a straight direction. Not applicable to trailers. In either case, improper caster adjustment will not wear a tire.
What will cause a tire to wear in only one spot and not all around then? Centrifugal force is trying to throw your tire off the rim at 180 degrees to the tire rim (straight off). If the force is equal all around the rim, the tire is stretched equally all around the rim for 360 degrees. This provides a perfect (or close to) circle for the rim to rotate around resulting in a smooth ride. Unfortunately tires are not manufactured close to perfect so a tire may have a bit more rubber in one spot than another. This will make that one tire spot heavier resulting in more force at that point being thrown outward when it is spinning down the road on your trailer. Does it make sense then that the one heavy spot will hit the road harder? And it will hit with a thump. This will give you wear in only one spot on the tire. The point where the tire is heaviest. Get to speed and you have the thump happening so often it feels like a vibration-- leading to getting your tires balanced. Your tire tech will spin that tire, find where the heaviest point is and counter-balance the heavy spot with a wheel weight 180 degrees opposite the heavy point. At speed, the weight should equal the same force as the tire heavy point is exerting resulting in a balanced tire.
Now that the geometry is explained how do your numbers read? I don't know your alignment specs for your trailer, however, some positive toe-in (+) is usually required. When you travel down the road the toed in tires try to straighten out this takes up any slack in the bearings etc.. Camber is usually called for to be also positive (+). As weight is applied into the vehicle the axles bend down, pulling the top of the tire in, so they run in an almost zero degree camber. This puts the entire tread on the pavement, not just the edge.
There is never an exact number for steering geometry. The specs will give you a number with a plus or minus value. (eg: 1/4 degree, plus or minus, 1/8 degree) It is the skill of your technician to determine which way the 'preferred' number should go.