Caster Adjustment

Does anyone know of a good video on caster adjustment for my 84 CJ7? Trying to make my Jeep a little more highway worthy. It’s really not to terrible bad now but i do have a little left/right darting that I’d like to solve.
Has a 4” BDS suspension lift and revolver shackles. I’m following someone’s recommendations that make absolutely sure that i have 6 degrees of caster. Just don’t really understand the math behind it nor do i understand how to go about making the adjustment. Thanks in advance.

 

The caster adjustment on these Jeeps is done with tapered shims placed between the spring pack and the spring mounts on the axle housing. This rotates the housing changing caster.
Caster is an alignment angle measured between the steering knuckle upper and lower pivot points. In this case the ball joints. If you extend the line drawn down to the road surface the intersection with the road should be in front of the center of the tire. If the line is perfectly vertical you have 0* caster. If the line intersects in front of the center of tire you have positive caster. If it intersects the road behind the center of the tire you have negative caster. If viewed from the side the top ball joint leaning back farther than the bottom is positive caster.
You want positive caster because the tire and wheel wants to follow the pivot point. Think of a shopping cart caster and how the wheel follows the pivot point. Same concept. Sorry but I don’t have a video to show but I’m sure there is plenty on YouTube.

 

That’s a damn fine explanation Nick and thanks. I did some looking and a lot or reading and if i add some 4 degree shins to the caster it’s gonna make my pinion angle around zero. Reckon that’ll be OK?

 

You want 5 to 7 degrees positive caster. Zero degrees will be unstable. Won't go straight, wheel won't return and you may have wobble, even bad wobble.

Think of an Easy Rider motorcycle. The front forks have something like 45 degrees positive caster. Vertical forks would be zero degrees. Recall Dennis Hopper riding no hands? That's because of the large positive caster angle. Choppers are very stable on the highway - the main reason why the forks are like that.

Do you have a measurement of the caster now? You need to measure. If you can't measure yourself, take the Jeep to a tire shop and have it aligned. They can only change the toe-in and center the steering without a big up-charge. Ask for the machine printout. That will tell you the caster now. Then add shims to get in that 5-7 degree positive range.

 

Depending on how much lift you have pinion angle should be fine. Like Timgr said, you need to know what caster is now and shoot for that 5-7 degree range. A regular construction angle finder on the bottom ball joint can be pretty darn close. Not as accurate as an alignment machine but still pretty close.