Leaf Spring Caster Shims - JeepForum.com

 
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post #1 of 9 Old 10-21-2010, 09:25 PM Thread Starter
josh86k10
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Leaf Spring Caster Shims

I recently purchased a beautiful '85 CJ7 (258/T176/D300/D30/AMC20 and my very first non-XJ Jeep). The PO installed what appears to be a 1.75" shackle lift with 31's. Unfortunately, funds are a bit tight until I recover from the initial vehicle purchase. While I am not a fan of the shackle lift and will eventually install a proper 2.5" spring lift, fixing the caster angle inexpensively is priority right now.

My current caster angle is 0.7 degrees negative. So, I need a 6 degree shim to be within factory specifications.

Without getting into a debate about the safety of axle shims in general, is a 6 degree shim pushing it? Seems like it will be a pretty thick shim. Should I go with a 4 degree shim and just get in the ball park or go ahead with the 6 degree shim? Obviously, I am referring to a steel shim which is incorporated into the leaf pack via the center pin. I will also be replacing the u-bolts.

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post #2 of 9 Old 10-21-2010, 09:59 PM
gojeepin
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There are other ways to change caster but if you're set on shims, use steel shims, get new (longer) centering pins, and bolt the shims into the spring pack.

Vibration? Bump steer? Wandering? Read the article (sticky) on Steering, suspension, and driveline.
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post #3 of 9 Old 10-21-2010, 10:22 PM Thread Starter
josh86k10
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I realize that repositioning the perches or rotating the knuckles are better options for a permanent solution. However, as I eventually plan to replace this somewhat sketchy shackle lift, I need something easily reversible and inexpensive.

I do not believe that shims are inherently dangerous when incorporated into the leaf pack; however, I do feel that there is probably a limit to how thick one should go due to altered forces on the center pin (it will now be "clamping" an angled surface; I have seen people shim both sides of the spring opposite one another to alleviate this abnormal force). My question relates to whether or not a 6 degree shim up front is approaching or exceeding this theoretical limit.

In short, assuming you think degree shims are safe, do you think 6-degree shims are safe?

Last edited by josh86k10; 10-22-2010 at 05:53 AM.
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post #4 of 9 Old 10-21-2010, 10:45 PM
cjdogtoy
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maybe I misunderstand your description, but I thought the spec. was 5 degrees positive witch would imply a 12 degree shim?
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post #5 of 9 Old 10-22-2010, 05:49 AM Thread Starter
josh86k10
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factory spec is 5-7 degrees positive. I am currently at 0.7 degrees negative.

-0.7 + 6 = 5.3
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post #6 of 9 Old 10-22-2010, 06:54 AM
gojeepin
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Steel shims are considerably thinner than aluminum and I wouldn't recommend aluminum for any reason (front or rear).

I used 10* shims in the rear before I completely rebuilt the CJ, but I sheared the centering pin and the spring pack started coming apart. I relocated the perches when I rebuilt it.

Vibration? Bump steer? Wandering? Read the article (sticky) on Steering, suspension, and driveline.
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post #7 of 9 Old 10-22-2010, 01:23 PM
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I would replace the shackles with near-stock length to improve your caster and deal with whatever flare rubbing that ensues until you get your 2.5" lift.

The other option I would consider (while I hate body lifts in general) is stock shackle length and a 1" body lift. No more.


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post #8 of 9 Old 10-22-2010, 01:27 PM
gojeepin
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I agree. I really don't like shims. Use a 1" body lift and the standard shackle.

BTW... to get 1.75" of lift from the shackle they'd have to be 3.5" longer than stock.

Vibration? Bump steer? Wandering? Read the article (sticky) on Steering, suspension, and driveline.
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post #9 of 9 Old 10-22-2010, 04:41 PM
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Quote:
Originally Posted by gojeepin View Post
BTW... to get 1.75" of lift from the shackle they'd have to be 3.5" longer than stock.
Correct. I misspoke.


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