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Setting Control Arm Length Without a Chart

MrSimon

MrSimon

NAXJA Forum User
Location
Downingtown, PA
I just raised the front of my MJ, and depending on how I measure, I'm at somewhere between 5 and 6.5". I put in adjustable upper and lower control arms and set them to to 15.25U and 16.75L.

I put the wheels back on and it seems like the axle is too far towards the rear.

I would like to adjust the arm lengths to get the wheels centered in the wheel wells. How do I do that without using a chart? I don't want to mess up castor and pinion angles.

Also, I don't really understand castor and pinion agles and how to adjust them (yes, i searched, but a lot of what I found just confused me more.)

So, how do I adjust my control arms, castor, and pinion angle to get my axle centered and the wheels where they need to be?
 
MrSimon said:
I just raised the front of my MJ, and depending on how I measure, I'm at somewhere between 5 and 6.5". I put in adjustable upper and lower control arms and set them to to 15.25U and 16.75L.

I put the wheels back on and it seems like the axle is too far towards the rear.

I would like to adjust the arm lengths to get the wheels centered in the wheel wells. How do I do that without using a chart? I don't want to mess up castor and pinion angles.

Also, I don't really understand castor and pinion agles and how to adjust them (yes, i searched, but a lot of what I found just confused me more.)

So, how do I adjust my control arms, castor, and pinion angle to get my axle centered and the wheels where they need to be?
Click to expand...

After a certain amount of lift (~4.5"), there's no saving "axle center" by using short/mid arms. You'll either center your axle and lose proper geometry, or don't and lose steering and create rubbing problems.

Since you already have full adjustables, I'd suggest looking into drop brackets...
 
the angles are already messed up.

at that height, you really need control arm drop brackets, but since you dont, increase the length of the lowers so the axle is centered in the wheel wells and use the uppers to adjust caster and pinion. pinion is the angle of the pinion coming out of the axle and caster is basically the angle of the steering knuckle. the angle of the knuckle is found by taking a straight edge from the bottom ball joint to the top balljoint.

at the height your at, you most likely cant keep them in spec with relation to one another. what you want is to have the pinion as close to spec as possible with the caster angle less important.
 
Yep, good advice on the drop brackets. I used Rough Country's (half the price and just as strong as anybody's) and they moved the axle forward about two inches, using the same c/a lengths.

Of course, at 6" of lift, you will have to compromise between caster and pinion angles, no matter how you mount the axle: Shortarms, dropbrackets, even longarms.

The only way to get "ideal" angles, would be to cut and rotate the knuckles.

And you don't want to bother with that.

Robert
 
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