by AzDon Wed Oct 12, 2016 5:32 pm
If the van is going to be level, 8 degrees might be a little excessive, but if you are going to have a hotrod nose-down rake, some of those degrees will go to the rake........Basically, caster is the kingpin angle front-to-rear, as viewed from the side with the brake backing plate removed....
When the bottom of the kingpin is farther ahead than the top you have positive caster. A forward rake rolls the front axle forward, subtracting from any positive caster you had..... This will reduce the van's preference for going straight down the road by default and instead of steering off from the center, you will have to "corral" it back to center constantly....... Positive caster allows you to take your hands off the steering wheel in confidence of going straight...
Caster can be easily measured at home using a magnetic dial protractor from the hardware store ($20 maybe?) and a six inch long piece of angle (2"x 2")
What you will do is stand the piece of angle on one ear against the flat mounting surface of the top of the axle right against the u-bolts with the flat of the angle up and parallel with the ground....You will use the flat to stick the magnetic mounting base of the protractor and read it....
Backing up some, you will want to be on a level surface with properly inflated tires and the van loaded to ride and set to your preferred rake. Use your protractor to first measure the level of the surface, because you will want to compensate the van's measurments for any degrees of unlevel in that surface.....
Ideally, You will want about four degrees of net positive caster to get good stability going down the road..... Wedge shims are used on top of the axle with the thick end to the rear to achieve positive caster..... Good Luck!
