JK Caster and Pinion angles - JeepForum.com
 
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post #1 of 4 Old 10-24-2019, 09:10 AM Thread Starter
dlm
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JK Caster and Pinion angles

I have a 2015 JKUR with the Mopar Stage 3 lift kit and have been trying to improve my steering. After installing new ball joints, tie rod and drag link I got an alignment and found my caster was only 3.2 degrees. My lift kit doesn't have adjustable control arms, so I was considering replacing my lower and/or upper front control arms with adjustable ones so that I can dial in more caster. Awhile back I replaced my front stock driveshaft with an Adams 1310 Extreme. I'm wondering how much I can sacrifice pinion angle to gain caster without jeopardizing long term reliability of my shaft or driveline vibrations. I'm attaching pictures of various angle measurements. It looks like the angle between my pinion and driveshaft is already about 8 degrees, if I were to install adjustable arms and dial in, say 6 degrees of caster, then I'd have almost 11 degrees between my pinion and driveshaft. Is that too much? I don't want to jeopardize its longevity or get vibrations. Do you think I could gain enough caster to make replacing control arms worth it?

Thanks!

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post #2 of 4 Old 10-24-2019, 01:32 PM
222Doc
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4.5 is caster target for stock wheels and larger can be a bit less. As long as you have NO vibes you can add caster. if doing so makes it vib dial it back. you always try to get as much of the caster you can with NO vibes for the max speed you travel. If you gear it this will effect what that speed is. example 4.1 gears can have more MPH then say 5.13 will be able to do since the drive line speed goes up. there is no magic number here too. seems to vary with each jeep as well.


steering at 3" lift. issues tends to be the angle of the drag link. the higher that angle is from stock the more vague steering gets. I run a 4.5" lift and went with a Flipped drag and raised track bar axle side. since flipping the drag makes that 3" of less angle. You must then raise the track equally 3" or you end up with Bump steer. more then a few kits for this. Though to run these kits you need 3" of bump stop or the track bar hits the frame. since taller lifts tend to need at least 3" of bump for the shocks to not become the bump anyway. with what i have now i have a 50/50 split of 11" travel.

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post #3 of 4 Old 10-24-2019, 03:52 PM Thread Starter
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Thanks for the reply!

Quote:
Originally Posted by 222Doc View Post
4.5 is caster target for stock wheels and larger can be a bit less.
Did you mean larger wheels can have more caster?

Quote:
Originally Posted by 222Doc View Post
As long as you have NO vibes you can add caster
So is it safe to assume that if I'm not feeling driveline vibrations, then I don't have to worry about driveline wear/damage from too much pinion angle?
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post #4 of 4 Old 10-24-2019, 07:12 PM
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oddly they can use less but i would still be at least 4.5 if it dont vib at what ever your top speed rolling down freeway is. The fact you have a angle finder is great as most people just ask never measure and want a simple answer.

If your new drive shaft has Zerk fittings be sure to grease them as well that centering ball. i would do it at least every other oil change. The centering ball can be PITA of front of a JK. at least on mine there is no way to get to it since its so close to the body. What i do for that is remove the front of the shaft from the yoke and suspend it as high as you can that will open up the space to get a needle in there.<<< PITA. rear is easy pezzy.


since the drive shaft front is in a no load. they can handle not being set up like one MUST in the rear. when they are in use in 4x4 under load speed tends to be low enough it wont vib. remember the more caster the worse that angle gets on the drive shaft too. if you are at 3.5 caster and say try 6 you may well have issues. 3.5 is not to bad really on a jk with larger tires. UNLESS you have issue that are from that angle.

i think you have a steering issue though is not caster. No caster or very low will make it not want to return to center after making a turn. It can add to a wobbles issue if it had that as well. but the vague to twitchy feeling is that steep drag link. stock they are at rather high angle add 3" it much steeper. The flip mode will do another thing as well by make the roll center bias way better. that is the way the axle moves left and right during cycling up and down. In a perfect world that track bar would be level to the earth. this way the movement is the least it can be. In a jeep its not a real big deal since no one is running them at Talladega. where axle shift at 200mph can be an issue.

i would think that buying adjustable arms may do less then the steering mode here. as well you can just get uppers to fix this. cost is way less. But having both you can then adjust track and angle. to perfection. as you lift a jeep the track gets shorter. BUT careful here as making longer may cause binding. A 2 door stock at ride height is 95.6" C<>C. at 4.5 inch of lift this gets shorter more so in the rear since the arms rear are shorter. at 4.5 lift on the ground im at 97" now mostly rear is pushed back and that takes more changes to do that.

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