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Thread: Axle Upgrade/Minimum Scrub Radius

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    Hooked JJ151's Avatar
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    Axle Upgrade/Minimum Scrub Radius

    Installed brand be Dynatrac XD60s a couple weeks ago and cant seem to figure out why I have death wobble above 45mph. Installed new MetalCloak adjustable control arms and trac bar on AEV 4.5 coil springs. New wheels are Hutchinson beadlocks with 5.28 of backspace. Based on videos Ive seen from Dynatrac and on this forum it seems that this combination creates a very tight scrub radius. In my case its about 0.5. The alignment shop is now telling me after my second alignment adjusting caster from 6 degrees to 7.5 degrees that I should only have a backspace of 3.5-4 My question is does or can having a smaller near zero scrub radius cause death wobble?


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    Meme King WJCO's Avatar
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    Something has to be loose somewhere for death wobble to occur. Double check that all bolts are torqued properly and no parts have play.
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    Resident Smartass OverlanderJK's Avatar
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    Quote Originally Posted by JJ151 View Post
    Installed brand be Dynatrac XD60s a couple weeks ago and cant seem to figure out why I have death wobble above 45mph. Installed new MetalCloak adjustable control arms and trac bar on AEV 4.5 coil springs. New wheels are Hutchinson beadlocks with 5.28 of backspace. Based on videos Ive seen from Dynatrac and on this forum it seems that this combination creates a very tight scrub radius. In my case its about 0.5. The alignment shop is now telling me after my second alignment adjusting caster from 6 degrees to 7.5 degrees that I should only have a backspace of 3.5-4 My question is does or can having a smaller near zero scrub radius cause death wobble?


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    So the increased caster and told you to get wheels with less backspacing? Sounds to me like that shop really knows what they are doing. Maybe have them work on a Barbie hot wheels instead.


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    Administrator wayoflife's Avatar
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    Quote Originally Posted by JJ151 View Post
    Installed brand be Dynatrac XD60s a couple weeks ago and cant seem to figure out why I have death wobble above 45mph. Installed new MetalCloak adjustable control arms and trac bar on AEV 4.5 coil springs. New wheels are Hutchinson beadlocks with 5.28 of backspace. Based on videos Ive seen from Dynatrac and on this forum it seems that this combination creates a very tight scrub radius. In my case its about 0.5. The alignment shop is now telling me after my second alignment adjusting caster from 6 degrees to 7.5 degrees that I should only have a backspace of 3.5-4 My question is does or can having a smaller near zero scrub radius cause death wobble?
    WTF? Ummm, I think you need to find yourself a new shop. MORE back spacing is what you want and near zero scrub radius is AWESOME and desired. Not only will it make turning easier and better, it'll also help protect things like your ball joints and help keep them and your wheel bearings from wearing out prematurely.

    Death wobble is caused by loose or worn out steering and/or suspension components - PERIOD. If everything is new on your Jeep, you most likely have a bolt or two that isn't tightened to torque spec. If everything is, the quality of your components probably suck and they're allowing for too much movement in the bushings or are flexing. You should NOT need anything more than factory caster and that's 4. If you have 6, that should be awesome and no more is needed.

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    Hooked Braxtonsag's Avatar
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    Are you sure its death wobble and not bump steer?

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    Hooked JJ151's Avatar
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    Quote Originally Posted by Braxtonsag View Post
    Are you sure its death wobble and not bump steer?
    Certain its death wobble. Have to come to almost a complete stop to get it to stop oscillating.


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    Hooked JJ151's Avatar
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    Quote Originally Posted by wayoflife View Post
    WTF? Ummm, I think you need to find yourself a new shop. MORE back spacing is what you want and near zero scrub radius is AWESOME and desired. Not only will it make turning easier and better, it'll also help protect things like your ball joints and help keep them and your wheel bearings from wearing out prematurely.

    Death wobble is caused by loose or worn out steering and/or suspension components - PERIOD. If everything is new on your Jeep, you most likely have a bolt or two that isn't tightened to torque spec. If everything is, the quality of your components probably suck and they're allowing for too much movement in the bushings or are flexing. You should NOT need anything more than factory caster and that's 4. If you have 6, that should be awesome and no more is needed.
    Thats what I thought. Dynatrac says 6 degrees too.


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    Axle Upgrade/Minimum Scrub Radius

    Here are 4 pics of the front upper control arms. The first 2 are the passenger and the second two are the drivers side. Both sets are on the axle. It looks like there arm sleeve isnt seated properly? Im not a mechanic so am not sure. For those of you that do installs, whats your opinion?

    IMG_2610.JPGIMG_2612.JPGIMG_2613.JPGIMG_2614.JPG


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    Meme King WJCO's Avatar
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    Quote Originally Posted by JJ151 View Post
    Here are 4 pics of the front upper control arms. The first 2 are the passenger and the second two are the drivers side. Both sets are on the axle. It looks like there arm sleeve isnt seated properly? Im not a mechanic so am not sure. For those of you that do installs, whats your opinion?

    IMG_2610.JPGIMG_2612.JPGIMG_2613.JPGIMG_2614.JPG


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    That bushing that looks like it isn't pressed in all the way in, actually it is. OEM or aftermarket, that is ok; that's how it is.

    Check to ensure ball joint nuts are tight and track bar bolts are torqued properly to 125 foot pounds. Check drag link and tie rod nuts also. And of course ensure your lug nuts are tight.
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  10. #10
    Meme King WJCO's Avatar
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    Just to make you feel better, here's an OEM axle and a prorock showing that same bushing.

    IMG_20190407_144404_167.jpg

    IMG_20190407_144436_953.jpg
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