Caster?
- Thread starter Nitmare2k
- Start date
RESURECTIONJK
Hooked
Factory Caster is I believe about 4.8-5.0 if I’m not mistaken. (A google search might be a good idea to be sure) With a 3” lift, in order to regain that back you’ll have to lengthen both upper and lower front control arms.
There are a few opinions on this but, when I was installing kits for a local offroad shop, we used to try and get the JL’s to at least 5.5-6.0 or at least, as close to it. We had good results with this measurement and it seemed to suit the majority of people. With the FAD, driveline vibrations aren’t as much of a concern. The more caster you have, typically the better and more responsive the steering will be. I run 7.8 on my JKU for a reference but, I have an aftermarket housing that has extra caster built in so I can get away with a higher positive number.
It’s simple to figure out on your own. You can use a magnetic angle finder or, there are a few angle finder apps for smart phones. You can use the top of the ball joint as a reference point or, the bottom of the end forging on the flattest point. Make sure to zero it out for the surface you’re on it it’s not level. This will get you pretty close if you take your time. Just be sure to make small adjustments to BOTH driver and passenger side equally. Take measurements and write down what your starting and end points are.
There are a few opinions on this but, when I was installing kits for a local offroad shop, we used to try and get the JL’s to at least 5.5-6.0 or at least, as close to it. We had good results with this measurement and it seemed to suit the majority of people. With the FAD, driveline vibrations aren’t as much of a concern. The more caster you have, typically the better and more responsive the steering will be. I run 7.8 on my JKU for a reference but, I have an aftermarket housing that has extra caster built in so I can get away with a higher positive number.
It’s simple to figure out on your own. You can use a magnetic angle finder or, there are a few angle finder apps for smart phones. You can use the top of the ball joint as a reference point or, the bottom of the end forging on the flattest point. Make sure to zero it out for the surface you’re on it it’s not level. This will get you pretty close if you take your time. Just be sure to make small adjustments to BOTH driver and passenger side equally. Take measurements and write down what your starting and end points are.
As mentioned and on a JL or JT, caster is set to just shy of +5° from the factory. To me, this is plenty but more will give you a tighter feel at the steering wheel and help keep your Jeep tracking straight at highway speeds.
I will have to disagree with the lengthening "both" upper and lower front control arms in order to regain that though. Your lower control set the position of your axles and your upper arms set caster up front and pinion in the rear. Proper position setting is determined at full bump and in spite of your axle "looking" off center in your wheel wells at ride height when lifted, if you have to remember that your axle travels in an arc. If you extend your lower arms too much, your axle bump pads will MISS the bump stop extensions at a full bump. Only a minimal amount of lengthening of the lower arms should be done and only to help make things look better - not for caster setting. Shortening your front uppers only is what you should be doing to set more positive caster.
I will have to disagree with the lengthening "both" upper and lower front control arms in order to regain that though. Your lower control set the position of your axles and your upper arms set caster up front and pinion in the rear. Proper position setting is determined at full bump and in spite of your axle "looking" off center in your wheel wells at ride height when lifted, if you have to remember that your axle travels in an arc. If you extend your lower arms too much, your axle bump pads will MISS the bump stop extensions at a full bump. Only a minimal amount of lengthening of the lower arms should be done and only to help make things look better - not for caster setting. Shortening your front uppers only is what you should be doing to set more positive caster.
RESURECTIONJK
Hooked
Eddie makes a good point here about the bump stops that I certainly missed. Typically at the shop we would adjust both uppers and lowers to keep the axle more centered as it drooped in hopes of limiting binding but, this was usually at the request of the customers. Eddie is correct. If you’re goal is to set caster, uppers are the only ones that need to move.
Another easy way on a JL or JT is to put your angle finder on you round front diff spreader holes cast into the housing either side of the cover . When it is at 0 or 90 degrees depending on your angle finder your caster is at 6 degrees which is better than stock on any model JL or JT . Naturally you can figure what you may actually have by knowing this as a reference . That also puts your front pinion at 0 degrees which seems to be OK with an OE drive shaft with only 2-3" lift on a stock front axle housing . Its slightly more caster than factory, works for me and have read that same fact numerous times by known respected members on Jeep forums . As far as adjusting caster it can be done with either uppers or lowers or a combination of both . MOPAR provides new 1/4" longer lower control arms with their 2.5" lift kit . Rancho Geometry Correction brackets as many brand brackets do adjust caster with the uppers while using OE length lowers. Many people only have adjustable lowers, nothing wrong with the little lengthening to get caster in the ballpark with them alone , as always watch pinion angle in the process. If I have adj uppers and lowers I use both to fine tune pinion angle , and bump stop alignment on OE axle housings with only 2-3.5 " lifts. Its not really an issue to get 6 degrees positive caster that I have seen or heard of..
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