Will control arms fix flighty steering?
Thread Starter
JK Freak
Joined: Apr 2010
Posts: 503
Likes: 0
From: Riverside, CA
Yes. From your profile, you are running 2.5" coils plus 1" coil spacers for 3.5" front lift.
As a result, your alignment caster specs are very low, creating flighty steering.
A combination of adjustable front lower control arms to return your caster specs to more than 4 degrees, correct toe-in alignment specs, and 30 psi or less tire pressure will fix he flighty steering.
Also, at 3.5" front lift, you want an adjustable front trackbar to center your front axle.
As a result, your alignment caster specs are very low, creating flighty steering.
A combination of adjustable front lower control arms to return your caster specs to more than 4 degrees, correct toe-in alignment specs, and 30 psi or less tire pressure will fix he flighty steering.
Also, at 3.5" front lift, you want an adjustable front trackbar to center your front axle.
JK Jedi Master
Joined: Jan 2008
Posts: 11,463
Likes: 165
From: Austin <--> Colorado Springs
You will want adjustable upper arms. Lower arms are used for centering the axle. If you try to adjust caster at the lower arms, you also will be turning your entire axle to the left or right a few degrees. The proper way to set caster is by tilting the axle using the upper arms making sure both lower arms are equal. Adjusting only the lower arms will affect the toe angle of both wheels at the same time to the same angle. In other words, if you need to make the right side longer than the left to gain proper caster, then the entire axle will be turned to the left. This is why cam bolts are no good either.
At 3.5 inches of actual lift, your spring perches will be misaligned by around 3/8s of an inch or more towards the rear. If you were just to go with upper arms, your already misaligned perches having to tilt backwards will cause the spring to bow into an S shape. You want your springs to be perfectly vertical the best they can be for proper compression and rebound of the spring.
At 3.5 inches of actual lift, your spring perches will be misaligned by around 3/8s of an inch or more towards the rear. If you were just to go with upper arms, your already misaligned perches having to tilt backwards will cause the spring to bow into an S shape. You want your springs to be perfectly vertical the best they can be for proper compression and rebound of the spring.
Uppers ands lower perform the same function. They both tilt the axle. You shorten adj uppers to raise caster, you lengthen adj lowers to raise caster. If you get both sets, you can fine tune and also move the entire axle forward or backward in the wheel well.
The problem with getting uppers only is that they do not have the range of adjustability that lowers have. (ie - you 'shorten' the uppers to raise caster, and many of the uppers out there will not adjust 'short' enough for higher lift heights.) So if you only get one set, lowers are the better choice. Another plus is that lowers are quite a bit more prone to trail damage than uppers, so replacing stock lowers with beefy aftermarkets is a good thing...
JK Newbie
Joined: Dec 2008
Posts: 61
Likes: 0
From: Winnipeg
Nice explanation Planman. I lengthened my front lowers 3/8" after lifting the front 3". I could not believe the improvement in steering stability!
The difference was so dramatic (and safer) that caster correction should be factored into every jk lift. Too bad adjustable arms are so expensive.
The difference was so dramatic (and safer) that caster correction should be factored into every jk lift. Too bad adjustable arms are so expensive.
JK Enthusiast
Joined: Aug 2009
Posts: 126
Likes: 0
From: Olathe Ks
So just to verify!!!
I have a similar setup as the OP. I have the TF 2.5", coil kit so it came with the 1/2" spacer in the back. 1" of spacer up front for the winch/bumper weight. I now think I have a little reverse rake, so I was going to put a 1" in back and remove the 1/2" spacer. Planning all this because I am going with a different bumper soon.
So based on the above description, lower fronts will help with handling and alignment, and lower rears would help me get my rear wheel centered again... right?!
I have a similar setup as the OP. I have the TF 2.5", coil kit so it came with the 1/2" spacer in the back. 1" of spacer up front for the winch/bumper weight. I now think I have a little reverse rake, so I was going to put a 1" in back and remove the 1/2" spacer. Planning all this because I am going with a different bumper soon.
So based on the above description, lower fronts will help with handling and alignment, and lower rears would help me get my rear wheel centered again... right?!
JK Enthusiast
Joined: Feb 2008
Posts: 221
Likes: 0
From: Colorado Springs, CO
I have a similar setup (TF 2.5 Coil Lift) and the jeep was wandering all over the place on the highway. I found a great deal on a set of Rock Krawler adj. front upper and lower arms. I also added an adj. front trackbar. It's made a huge difference!
I don't feel like I'm fighting with the jeep to keep it in the lane anymore. I feel much safer and would encourage anybody with the flighty-ness to add at least front lower arms and a front trackbar. I think the upper arms probably aren't a necessity, but they will just give you more adjust-ability.
I don't feel like I'm fighting with the jeep to keep it in the lane anymore. I feel much safer and would encourage anybody with the flighty-ness to add at least front lower arms and a front trackbar. I think the upper arms probably aren't a necessity, but they will just give you more adjust-ability.
Trending Topics
Thread Starter
JK Freak
Joined: Apr 2010
Posts: 503
Likes: 0
From: Riverside, CA
Back from 4 Wheel Parts
Went and priced everything out. Front upper and lower Teraflex control arms, adj. trackbar, and swaybar discos with install for about $1300 (they are running a half off install later this month). Does this sound like a good deal? Can probably get them down a little more but wasn't ready to buy yet so didn't bother haggling.
JK Jedi Master
Joined: Jan 2008
Posts: 11,463
Likes: 165
From: Austin <--> Colorado Springs
How is your front driveshaft holding up? You may want to go flex and check the clearance 'before' taking it out in the boonies and disconnecting for the first time. You may be in for a little surprise from the added droop... 