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Attention to the TJ owners 1996-2006 NEW LED LIGHT OPTIONSOPTIC ARMOR WINDOWS all sale now !!!!!!!!FS: 2007-2013 Jeep Wrangler "HALO" Angel Eye Kit

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Unread 03-05-2013, 08:30 AM   #16
JeeperDon
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1993 YJ Wrangler 
 
Join Date: Jan 2005
Location: Albuquerque, NM
Posts: 6,203
On another thread recently they were talking about caster angle and shackles. I did some more research and math after that. I found that less caster is needed with larger tires, since the tire/road contact point is further ahead of the knuckle swivel. The OEM spec for my YJ is 6.3 (+/-1), which turns out to be about 5 needed for a 35" tire (compared to a stock 29" tire).

Doing the caster math as it applies to shackles, changing the shackle length by 3/4" changes the caster angle by 1. So, lengthening a shackle from the stock 4" means lowering the caster, which means for twitchier on-road handling and poorer on-road return-to-center (Jeep seems to have a mind of it's own). My present shackles are 5.75" long, and my caster is about 3.5 (had it measured by a shop), and the Jeep indeed has a mind of it's own on-road.

Actually, today's garage project is to fab up a new pair of front shackles that are maybe 4.5" long to get my caster much closer to the 5 I figure is good. I think it's worth a couple hours of shop time and 2' of steel to experiment.

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Unread 03-05-2013, 09:11 AM   #17
Andywear
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1991 YJ Wrangler 
 
Join Date: May 2011
Location: Tulsa, OK
Posts: 1,243
4.5"lg with 3/8" bolt holes?
I guess Im asking what size dia. are the bolts?
wondering of how much meat will be needed around the edges
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Unread 03-05-2013, 09:32 AM   #18
tom_sprecher
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1991 YJ Wrangler 
 
Join Date: Dec 2012
Location: Marietta, GA
Posts: 335
Most heavy duty aftermarket are 3/8" x 2" steel with 1/2" bolt holes and a 1" end radius.
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