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Thread: JK Caster and Pinion angles

  1. #1
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    Question 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 I've made.

    What would an ideal caster be for my setup? I know a little more than the factory setup is preferred when you have a lift/bigger tires, I've heard anywhere from 5 to 7 degrees. Do you think I could gain enough caster to make replacing control arms worth it?

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    Thanks!
    Last edited by dlm_jku; 10-24-2019 at 02:18 PM.

  2. #2
    Nothing but a Thing MericaMade's Avatar
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    Yes, front lowers and rear uppers will get you better angles and adjustment ability. I recommend EVO control arms.

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    I understand that adjustable control arms will allow me to dial in more caster. 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.

  4. #4
    Meme King WJCO's Avatar
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    Quote Originally Posted by dlm_jku View Post
    I understand that adjustable control arms will allow me to dial in more caster. 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.
    You want your caster between 4 and 4.5 degrees. This is what factory calls for. Once you do that, your driveline angle will automatically be where it needs to. If you go higher on the caster, you will have improved steering but you could risk getting driveline vibrations.

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    Quote Originally Posted by WJCO View Post
    You want your caster between 4 and 4.5 degrees. This is what factory calls for. Once you do that, your driveline angle will automatically be where it needs to.
    That only works with no lift. This guys has a lift.


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    Administrator wayoflife's Avatar
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    Quote Originally Posted by fiend View Post
    That only works with no lift. This guys has a lift.
    This is wrong. Even with a lift, caster should be set at about 4°-4.5°. Less will cause flightiness at highway speeds. More would be ideal but as mentioned, that can cause driveline vibrations especially if you're running gears with a high ratio.

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    Quote Originally Posted by wayoflife View Post
    This is wrong. Even with a lift, caster should be set at about 4°-4.5°. Less will cause flightiness at highway speeds. More would be ideal but as mentioned, that can cause driveline vibrations especially if you're running gears with a high ratio.
    Thanks for the clarification! I've heard some conflicting information about this in regards to modified Jeeps. I currently have the stock 4.10 gears running with 295/70R18s (~34.5x11.5"), although in a few years I'd like to get up to 37s and 4.88 gears.

    In this case, do you think the improvement gained from adding a degree or so of castor is worth the expense of replacing lower control arms and getting another alignment?
    Last edited by dlm_jku; 10-24-2019 at 03:12 PM.

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    Administrator wayoflife's Avatar
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    Quote Originally Posted by dlm_jku View Post
    Thanks for the clarification! I've heard some conflicting information about this in regards to modified Jeeps. In this case, do you think the improvement gained from adding a degree or so of castor is worth the expense of replacing lower control arms and getting another alignment?
    If you're at 3.2° now, I personally would recommend that you install a set of adjustable lower arms to get you back up to +4°. That's what comes on your Jeep from the factory and that should help reduce flightiness at highway speeds. I would be reluctant to go higher than that especially if you're running 5.13 gears or higher.

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    Old Timer fiend's Avatar
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    Quote Originally Posted by wayoflife View Post
    This is wrong. Even with a lift, caster should be set at about 4°-4.5°. Less will cause flightiness at highway speeds. More would be ideal but as mentioned, that can cause driveline vibrations especially if you're running gears with a high ratio.
    I’m not disputing that caster should be at 4-4.5 degrees. I was responding to the comment that once you set the caster and this amount, the driveline will “automatically” be correct. If you have a lift and a stock axle, that’s not necessarily true. That’s why Dynatrac and other aftermarket housing makers build in extra caster. For example:

    “The owners of some Jeep JKs have discovered that lifted rigs need a bit more pinion rise to minimize the possibility of drive shaft vibration. However, changing the pinion angle on a front axle housing, affects the caster angles which are important for handling and steering. Therefore, there is a practical limit to increasing the pinion angle adjustment.

    Our new Unlimited ProRock 44 is built to allow an increased pinion angle but retains or even increases factory caster angles. This helps prevent drive shaft vibrations and can improve on-road handling substantially.”


    https://project-jk.com/jeep-jk-news/...-forum-members


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    Quote Originally Posted by fiend View Post
    I’m not disputing that caster should be at 4-4.5 degrees. I was responding to the comment that once you set the caster and this amount, the driveline will “automatically” be correct. If you have a lift and a stock axle, that’s not necessarily true. That’s why Dynatrac and other aftermarket housing makers build in extra caster. For example:

    “The owners of some Jeep JKs have discovered that lifted rigs need a bit more pinion rise to minimize the possibility of drive shaft vibration. However, changing the pinion angle on a front axle housing, affects the caster angles which are important for handling and steering. Therefore, there is a practical limit to increasing the pinion angle adjustment.

    Our new Unlimited ProRock 44 is built to allow an increased pinion angle but retains or even increases factory caster angles. This helps prevent drive shaft vibrations and can improve on-road handling substantially.”


    https://project-jk.com/jeep-jk-news/...-forum-members
    LOL - guess you've been thinking about this for a while but really, I can't say I understand why especially being that you're "not trying to dispute" what caster should be.

    As Dynatrac points out, caster angle is IMPORTANT for handling and steering and this is true REGARDLESS if you have a lift or not. 4-4.5° IS what the OP needs in order to "IMPROVE HIS STEERING" especially being that he has a lift. The perks Dynatrac offers on their ProRock axles are just that, perks - not some kind of doctrine.

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