I have an 09 Rubicon Unlimited with a 4" teraflex lift and upper and lower control arms and 37's. I set the front lowers to 24" and the uppers to 19 1/2"(per instructions that came with the arms) After I lifted it I checked the angle , which with an angle finder, measured 4-5 degrees, same on both sides.
Also, when I installed the coast drive shafts front and rear, I lengthened the upper arms 4 turns to adjust the pinion angle. The pinion is still not straight in line with the drive shaft, but it is much better than it was.
I drove it for a couple of weeks and on the highway it drives pretty good, but on back roads (where I drive the most), it darts around every time I hit a bump or dip in the road. Is this a problem with caster or is this bump steer ???


Would someone who is running a lift and tires similar to mine tell me what lengths they have the upper and lower arms set and what caster they ended up with ? I am getting tired of playing around with the adjustment. Help!!

 

Go get it aligned. Those measurements in the instructions are just starting points. FYI I am running 37's and 3.4 degrees of caster. Also what psi are you running? If you have any questions, call me.

 

Wow 47's ehh

 

ummm, 47's - really??

 

Get those 47s off of a tractor or something?

 

47s??? Then judging by the relative size, you must have a pet mountain lyon

If you adjusted your pinion angle after measuring your Caster, then your current Caster angle is probably less. That is the tradeoff between pinion angle and Caster. You need to run as much Caster as you can get away with while still running a smooth double-cardan driveshaft.

 

oooooooops my bad. 37's not 47's.

 

Castor is going to be a wobble inducer, but, if when you hit a bump, it makes you dart, well, that's bump steer.

Bumpsteer is more related to the drag link not being parallel to the track bar.

When the suspension compresses, both the track bar, and the drag link, move in an arc...

...if the arcs are not the SAME or at least similar, the compression of the suspension will steer you ~ by the difference in the arc radii.

If you jack the front end up, and as its rising, look at the drag link and the track bar, and how each is moving as the suspension uncompresses/extends...and you will see a similar effect....

...then lower it, watching, and you will see it again...they two move in different arcs, and that pulls the steering to the short side.

On the road, when you hit the bump, the suspension compresses, steering you one way, then it extends again, steering you the other way...

...if you add some front end bounce after the impact, you have a few more darts this way and that..

...if you try to fight the darts, you are now introducing yaw and pitch of your own, which ALSO compresses/extends the suspension, but at opposite sides, adding yet ANOTHER set of oscillations to deal with, etc.



So get the drag link and track bar as parallel as you can, and that tends to cure bumpsteer.

 

I had very similar issues with my Tera 4" until I added the drag link flip kit - then bumpsteer went away.

 

If you don't mind my asking, which steering kit did you buy? How hard was it to install? Any special tools needed ? Hey thanks for your input.