I'm try to fix a problem with a wandering XJ. Back last August I installed a RE 4.5 kit and since than have been trying to allign it. My question is I've set my pinion angle at 5 deg., which makes my UCA lenght 15 1/4 (I have adj UCA only). How do I check my caster angle in relation to my pinion angle? RE say to set my caster angle at 5-6 deg. Just thought I'd see if anyone knows of a trick to doing so.

 

your caster is the angle related to an imaginary line perpendicular to the ground. take that imaginary line and put it intersecting your upper ball joint. now draw a line through both ball joints. the angle in between those two lines is your caster, as simple as i can put it. without an alignment machine, you can check it that way with an angle finder.

but did you rotate up your front axle? if you did, you definately lost your caster and that will take away directional stability.

 

grn99, just put an angle finder on top of the upper balljoint. Remove the zerk if it's in the way.

I used to know the degree of seperation from factory of the pinion and caster, but have forgotten. A google search might find it...or maybe NAXJA.

 

If you find this info post it so we can add it to the tech area for guture reference.

 

i'm sorry but putting an angle finder on top of your upper ball joint is not your caster angle. it might get you in the ball park, but all its really telling you is the angle of the top of your upper ball joint. but if you have something to compare that angle to, then you can use it for something.

caster is the angle of a line from both ball joints, not just the angle of one.

 

Yep, i goofed. I forgot the 90* difference off the line between balljoints.


I did some checking, the difference in pinion to castor is 9* on a HP30 according to Marcus (GoJeep). http://go.jeep-xj.info/HowtoAlignment.htm

I do get confused on this at times so if i make a wrong assumption please set me straight. Say you have a pinion angle of 13*, minus the 9* for a castor of 5*. Correct?

 

pinion angle and caster are totally seperate angles. but you can't change one without the other on a straight axle without cutting the welds tht hole the knuckle on and rotate and reweld them to bring caster back. this picture shows caster, the line between the two x's is the perepndicular line, and then the angled line is your angle between two ball joints.

http://upload.wikimedia.org/wikipedi...ster_angle.svg

i don't know wh i cant get the picture up, its in wikipedia if you search caster angle.