Hi everybody. OK, here's my situation: My 4 door JK is lifted a total of close to 6", and I am running 37's on 17x9 wheels. When we finished the lift up, we had the lower control arms the same length as stock, and drove it to see how it felt. It wasn't TOO bad, but did have some wandering in it, but everything else felt smooth, no signs of death wobble or any shimmys or anything. I drove it around a couple of weeks like that, until I had time to get back under it. Well, in an attempt to get rid of that slight bit of wander, I lengthened the lower control arms and got my caster to around 7 degrees, as I had around 4.5 or 5 degrees before setting the length of the control arms. After finishing up, making sure everything was torqued back to 125, and checked the track bars for tightness as well, and torqued them again, I drove it. Now the wandering was a lot less, nearly gone, to the point that I was pretty sure anything else I was feeling over rougher spots was just the larger tires pulling into ruts, etc...in other words it drove pretty nicely, BUT...all of a sudden, after driving for 2 weeks with absolutely NO shakes or shimmying, death wobble, etc...the instant I drive it after setting the caster to 7+, I feel a slight shimmy start at around 47 MPH, and carry on until about 53 MPH or so. I took the doors off, and drove it again, so I could watch the front tire, and upon taking off, it was perfectly true, straight, etc...but just when I start to get to 47 MPH, and feel the steering wheel begin to move slightly, I look at the front wheel, and see it beginning to move back and forth, very slightly, like the very beginning of a death wobble situation, but that's as far as it goes, just between 47 and 53 MPH, and never escalates into full death wobble, or anything, just a slight shimmy. Well, after looking around, under it, checked the unit bearings, TIGHT, ball joints, TIGHT, everything else also appears to be tight, so I'm stumped. I looked around on google and on here a bit to see what I can find, and I ran across this article, containg this paragraph, in JP magazine:

Alignment:
There are two schools when it comes to alignment. Too much caster and too much toe-in can induce death wobble. Too little caster and too much toe-out can cause wandering. Identify your symptom. If the tires start oscillating and hopping violently, you've got death wobble. Increasing the toe setting to as much as 3/8-inch toe-out (yes, readers toe-out; no misprint) has been known to help, or if possible, dialing the caster back to 3-4 degrees positive (bottom ball joint in front of top). The larger your tires, the less caster you should need. Read more: http://www.jpmagazine.com/techarticl...#ixzz1oHEOocnh

OK, going by that, theyre saying that I have too MUCH caster, but when I had 4.5 degrees, I had a wandering situation. I've read several places that JK's seem to like a bit more positive caster to handle well, so....does anyone think this may be the cause of what I started feeling right after increasing the caster? If so, I guess I can start backing the length of the arms down one turn at a time, and driving it until it stops, but it seems crazy to me, that this one article seems to go against everything else I've been reading on here about setting the caster.

 

You're approaching the upper limit of caster at 7 deg. Are you still running the stock front drive shaft? The more caster you have, the steeper the front pinion angle. The shimmy you describe could be front drive shaft vibration. There is a trade off with both...you might try backing the caster down to 5-6 deg and see if it helps.

 

I thought that an exceptionable caster was between 4 and 6. So you night want to try and dial it back a little. I would also check wheel balance, that's right at the point where that would come into effect.

 

Yes, stock front shaft, for now. I was thinking along the same lines as that, but would/could the driveshaft (if that's the cause) make the tires visibly begin to move in a shimmying motion?

 

Thanks. Yeah, with 4.5 degrees, I was experiencing a small amount of wandering, which went away with the increased caster, but I guess I will do like you say, and I mentioned in the original post, and start shortening the arms a turn or two at a time, until I find a happy medium. I was just curious if anyone had heard this, about too much causing shimmys and wobbles, because I had not.

 

Yeah, with a stock shaft that is too much caster. That may be what is causing your shimmy.