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caster degree

C

clayton3854

NAXJA Forum User
Location
Westfield MA
hello everyone I just got my jeep aligned after installing new steering and I was just wondering what the correct caster degree should be. im running 6.5" lift with RC long arms, 6" front coils, 4" full rear leafs with 2" shackle and shackle relocaters and rustys 1ton otk heim steering conversion. any other information needed just ask, thanks.
 
problem with "Correct caster" and lift is that with a lot of setups if you put the prescribed 6.5* of caster your pinion will be pointing down and youll fry u joints and pinion bearings.
although at 5" of lift i was able to dial in 4.5* just fine and it drives well
 
im at 5" of lift with around 5* of castor, works well.

i believe factory spec is somewhere in the range of 5.5-8.5? someone can correct me on that.

the problem for you being... your going to have to find the happy medium between proper castor and the driveline vibes and poor Ujoiun life associated with a bad pinion angle, as eflores said.

only other option are to install locking hubs or or rotate the Cs... or both for best results on and offroad. a poor pinion angle is still going to show itself if you need to lock the hubs for bad weather.
 
isnt it true a quick way to see if your caster is close is if the coil spring is parallel with the coil tower?

the xj in question is a little under 3* right now coil and coil tower are just about parallel and i am pretty sure pinion angle is spot on
 
VAhasnoWAVES said:
im at 5" of lift with around 5* of castor, works well.
i believe factory spec is somewhere in the range of 5.5-8.5? someone can correct me on that.
the problem for you being... your going to have to find the happy medium between proper castor and the driveline vibes and poor Ujoiun life associated with a bad pinion angle
Click to expand...
The 2001 FSM calls for 5.25-8.5 degrees of caster. It also calls for the front axle pinion angle to be 0.5-1 degree.
My 01 XJ had terrible front driveshaft vibrations, at freeway speeds, when the pinion angle was over 1 degree. I really noticed a difference when regearing to 4.56s. The increased driveshaft speed made the imbalance much worse. Setting the pinion angle to 1/2 a degree made all the difference, eliminating most or all of the vibs.
With offset lower ball joints, 5 degrees of caster is possible with a D30 LP, at 4' of lift, enough to make driving it at freeways speeds enjoyable. Any less and my XJ's steering has little or no return to center.
 
mcguyver_xj said:
caster has nothing to do with ball joints thats camber....caster is affected by lca's
Click to expand...

Adjustable(offset) ball joints will work to correct up to 2 degrees of caster or camber, depending on how you rotate them. You can rotate the knuckle or tilt it in or out.
Adjusting the control arms for 1/2 degree of pinion angle resulted in 3.25 degrees of caster. The Napa offset ball joints raised the number to 5 degrees...believe it or not.
http://www.napaonline.com/Catalog/C...le-Lower-Front-Susp/_/R-NCP2643724_0318416994
They have about 40,000 miles on them and are still tight. It's my DD, running 33"s.
 
lazyxj said:
Adjusting the control arms for 1/2 degree of pinion angle resulted in 3.25 degrees of caster. The Napa offset ball joints raised the number to 5 degrees...believe it or not.
Click to expand...

Did you use both upper and lower adjustables, or just the lowers lowers?
 
Talyn said:
Did you use both upper and lower adjustables, or just the lowers lowers?
Click to expand...

Yep, I know how to adjust both the upper and lower CAs. The D30-LP has the knuckle welded on in a different position than the D30 HP, making it difficult to achieve the proper caster when lifted.
I can rotate the axle to have perfect caster but then the pinion angle is way out, rotate it the other way to get the right pinion angle and have very little caster. Other than cutting and rotating the knuckles, there are few ways to increase the caster on a LP D30 other than using offset ball joints.
I should have change to a HP years ago...20-20 hindsight.
 
I've read that you need less caster with larger tires, and it has proven true for me. I'm on 37" MTRs, at about 4° of caster and it drives very well.
 
Last edited:
lazyxj said:
Yep, I know how to adjust both the upper and lower CAs. The D30-LP has the knuckle welded on in a different position than the D30 HP, making it difficult to achieve the proper caster when lifted.
I can rotate the axle to have perfect caster but then the pinion angle is way out, rotate it the other way to get the right pinion angle and have very little caster. Other than cutting and rotating the knuckles, there are few ways to increase the caster on a LP D30 other than using offset ball joints.
I should have change to a HP years ago...20-20 hindsight.
Click to expand...

Correct, but if you lift an XJ equipped with a HP D30 over 4.5", you will have the same issue to deal with. I swapped out my LP 30 for a HP 30 and at 6" of lift, eventually resolved to rotating the knuckles so I could have correct pinion angle and proper caster.

The most common options are to just deal with poor on-road handling, or run selectable hubs to take the vibes from incorrect pinion angle out of the equation.
 
XJEEPER said:
Correct, but if you lift an XJ equipped with a HP D30 over 4.5", you will have the same issue to deal with.
The most common options are to just deal with poor on-road handling, or run selectable hubs to take the vibes from incorrect pinion angle out of the equation.
Click to expand...

While the HP can work at higher lifts than the LP, neither axle has as much adjustment as is needed for bigger lifts.
I was fortunate to be able to get both the caster and pinion angles in an acceptable range, at 4" of lift, without cutting and rotating the knuckles or spending a small fortune for selectable hubs. The adjustable lower ball joints were the easiest way to get there and have proven to be durable in my application
 
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