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Unread 07-11-2012, 08:06 AM   #16
Agony Wagon
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1995 XJ Cherokee 
Join Date: Aug 2008
Location: , Ohio
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What does it take to get them the same length? What else do I have to buy???

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Unread 07-11-2012, 08:59 AM   #17
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1984 CJ7 
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Don't worry about that. The effect of unequal length arms will be imperceptible from the picture you showed.
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Unread 07-11-2012, 04:50 PM   #18
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2006 LJ Wrangler 
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Originally Posted by foggybottombob
I don't understand what any of this has to do with a plane as someone mentioned
Since everything else you said is nearly spot-on, I'll not muddy the waters, but will add this to clarify the "shared plane" concept. Notice in diagram 3 below the tb and dl are parallel, but not in the same plane (fore to aft) and not sharing a radial center, so their arcs of travel are not common and bumpsteer is inevitable. I hope it helps. Here's the link for the original thread: http://www.jeepforum.com/forum/f9/tr...tions-1356624/

Originally Posted by flying_bosun

At issue specifically was the "parallel" relationship required to avoid bump steer.

We've all heard that the TB and DL must be parallel and it's been suggested that with a DPA this could be accomplished by raising the axle end of the TB or by dropping the TB frame end. Initially this seemed reasonable to me from a geometric stand-point, but upon further examination it turns out not to be the case; the problem is that our axles articulate.

Here are some rough diagrams that may help some to understand what I mean.





For lack of a better explanation, bump steer occurs when the relative arcs' of travel don't share a (nearly) common center. This is because as the axle articulates, the push/pull forces acting on the axle via the track bar are at times contrary to the push/pull forces acting on the steering knuckle via the drag link.
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bump steer , track bar
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