I bought a Jeep with a DPA installed and it was all over the road. My wife wouldn't even ride in it with me. I changed it back to a stock one anyways.
LJ Rubicon still follows ruts in the road
- Thread starter toddsull
- Start date
I bought a Jeep with a DPA installed and it was all over the road. My wife wouldn't even ride in it with me. I changed it back to a stock one anyways.
I bought a Jeep with a DPA installed and it was all over the road. My wife wouldn't even ride in it with me. I changed it back to a stock one anyways.
I bought a Jeep with a DPA installed AND a track bar drop bracket...on the AXLE end. So the drag link was shallower and the track bar was steeper, doubling up on the bump steer, and to top it off the frame end track bar nut was loose so the taper was floating around in the mount. I white knuckled it the whole way home from Amarillo to Colorado Springs.
Not always caused by a DPA as mentioned above...
In preparation of the JKS 2" lift I put on, I took out the inverted T style steering I had, and put the Jeep 100% to stock suspension including all new steering and suspension parts (mind you I had no steering issues with this setup, I wanted to start from a neutral base). My lift did not come with a DPA, and I knew better than to add one. I get BS with "factory" geometry... it is apparent when I accelerate or brake hard, and also when I cross a depression or bump diagonally (like a ditch). It is not enough of a concern yet, but I do need to get it worked out. My jeep pulls to the left when accelerating, and to the right when braking, I know this is from the front suspension unloading, and loading during the respective events.
For those trust but verify types, my toe is set to 1/8", fornt axle is centered with the JKS Adj track bar, and the castor bolts are rotated fully forward. Rear axle has a TB relocation bracket. Tires are 33x12.5x15 on 8x15/3.5bs wheels. Maybe I'm getting scrub issue causing it? (can scrub radius even cause/mimic bump steer?)
I'm not trying to take away from the OP, but it seems he might have something similar to what I have going on.
OP
First, a big thanks to everyone that has commented and helped. Let me provide more information.
I bought the LJR 4 weeks ago and it barely made it to 30 mph before it was all over the road (got a great deal on it). We’ve replaced in the last 3 weeks the following:
My concern is that when I hit a dip or rise in the road, the front end feels like the tires are moving around and it telegraphs thru the steering. The steering is perfect with no dead spot or lag. Almost as if the front axle is shifting around. Hard to explain.
My thoughts are as follows (please add, comment etc. as I’m new to the LJR):
A) The LJR has a slight rake. About 1” from back to front. There’s a 1” spacer the PO added to the back springs. Could the rake cause the issue?
B) Could my KM3’s be bad? Build date is 2018.
C) The steering box was replaced by the PO and it feels very tight. Absolutely no play. Does the steering box need to be upgraded to handle the lift and tire combo? Is it allowing the tires to move (not holding the line)?
My uneducated guesses. Thanks everyone! This is driving me crazy….
I bought the LJR 4 weeks ago and it barely made it to 30 mph before it was all over the road (got a great deal on it). We’ve replaced in the last 3 weeks the following:
- Rebuilt the RockJock Johnny joints on the control arms (no one lubed those joints in years)
- installed CorrectLync steering system
- Installed RJ adjustable trac bar
- Installed Spicer ball joints
- Installed Spicer U joints
- Installed Timken hub assembly
- Set toe-in at 1/8” and caster at 6.3 degree's
- Fox 2.0 shocks
- Running TA KM3 at 28 psi (I’ll try 26 and 25 psi today). Tires are half gone and they feel very “crunchy” - beyond that of mud tires which we’ve had on several vehicles. 35X12.5X15 on stock rims which rub at full turn.
- Unknown springs
My concern is that when I hit a dip or rise in the road, the front end feels like the tires are moving around and it telegraphs thru the steering. The steering is perfect with no dead spot or lag. Almost as if the front axle is shifting around. Hard to explain.
My thoughts are as follows (please add, comment etc. as I’m new to the LJR):
A) The LJR has a slight rake. About 1” from back to front. There’s a 1” spacer the PO added to the back springs. Could the rake cause the issue?
B) Could my KM3’s be bad? Build date is 2018.
C) The steering box was replaced by the PO and it feels very tight. Absolutely no play. Does the steering box need to be upgraded to handle the lift and tire combo? Is it allowing the tires to move (not holding the line)?
My uneducated guesses. Thanks everyone! This is driving me crazy….
Those aren’t stock wheels. Are they 15x8 or 15x10? Backspacing? They’re completely outside of the steering which is never great. Probably have a tramlining issue exacerbated by poor excessive positive scrub radius combined with heavy 35” mud tires.
Proper toe for 35's is more like 3/16" of an inch....may not matter vs 1/8", however toe is an angle, not an inch measurement for a given tire size. The angle doesn't ever change.
Proper toe for 35's is more like 3/16" of an inch....may not matter vs 1/8", however toe is an angle, not an inch measurement for a given tire size. The angle doesn't ever change.
OP
Good to know. I thought they were (same as on my son's jeep). I just measured and they are 10" and from the face to the outer lip is 5.5" Not certain what that would be in backspacing. Can you explain what you mean by being "completely outside of the steering". I'm trying to learn (fast). The inside tire rubs on the Teraflex frame mount. Thanks!
The inside bead of the tire is outboard of the tie rod ends. This is how you measure backspacing.
Edit: if you draw a line through the ball joints it should hit the ground towards the center of the tires contact patch.when its set up like yours it allows the road to have more leverage on the steering
They are mostly somewhere in the 3.5-4” backspacing range which is measured like RickyD posted. Stock backspacing is 5.25” on 7” wheels and 5.5” on 8” wheels. Having a 10” wide wheel mounted 1.25-1.5” further out puts the center of the tire much further out than stock form, which significantly increases scrub radius. Scrub radius adds a higher moment force to the steering system which causes toe out and also just makes the tires more difficult to control.
Added tire height negates scrub radius so theoretically if you had a tall enough tire you’d be back to where you need to be, but 35” isn’t it.
My ideal setup on 35’s would be about 4.25-4.5” backspacing on an 8” wheel. Unfortunately on 15’s you’re limited in backspacing options, but you can definitely go with something other than 10” wide wheels.
All of this is why people obsessed with “stance” on modded vehicles don’t really know what good qualities in handling are, and they are throwing out good handling by chasing the stance they are so enamored with.
OP
Thanks for the info! Appreciate it. If I understand right, if I increase the backspace to pull the tires inward it will help with tracking. The tires already hit the TF sway bar frame and if the tires move inward, it will require the removal of the TF sway bar setup. I've seen a lot of the TF sway bar setups. Are all those TF setups requiring the tires to move outboard wrong or creating issues? Is there another, better setup to keep the TF sway bar?
My Jeep handles/tracks perfectly fine with no issues (7 years) with 10" wide wheels). My tires aren't as worn as yours either though.
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I'm not aware of anybody here running the TF sway bar. Lots of Rockjock AntiRock and ORO Swayloc. Hard to tell how far outboard that arm has to be to have all that mechanism business between it and the frame, but here's a couple photos of mine.
My inside tire hits the lower control arm well before the outside tire hits the SwayLoc arm. Note that SwayLoc puts the switch mechanism on the passenger side, where due to the arc of the track bar, the tire moves outward as it stuffs into the fender so there's more room to play with. In offroad situations with the front axle fully articulated, I get a little bit of contact just aft of the mechanism but it's not enough to rub paint off and it never happens on pavement.
I should also disclose I have a washer underneath each steering stop, which enlarges my turning circle by an indistinguishable amount but prevents harder contact where the tire lugs are grabbing stuff. I also have Cooper STT Pros which have a tread width about an inch wider than KM3s, so my situation should be worse than yours. It's possible I could run KM3s and get rid of my washers, and still have no hard contact.
This is 4" backspacing on 15x8 wheels. Your backspacing is probably about 3.5" which wouldn't be the end of the world on a 15x8 wheel, but then the 10" width is pushing the tire centerline another inch outboard. I have about an inch more scrub radius than stock...and you probably have another 1.5" beyond me.
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I wonder if the OP's issue could just be from the tires being "slightly crunchy" and hard, forcing them to follow the ruts more...
Looking at your setup, I see how the geometry is similar to mine... do you get the bump steer with hard braking and accelerating? I know that as the suspension loads and unloads it pushes and pulls the drag-link and will inherently steer the Jeep (bump steer) My JT did not do this, but the lift there did not appear to change the angle of the TB and DL as much as it did on the TJ. (and the longer wheelbase probably masks it a bit too...) So, if you hit the gas hard, does your TJ want to pull left, and when you hit brakes moderately hard, does it pull right?
shouldn't rule it out.
There's going to be some bump steer even in the "perfect" stock steering but lifted TJ setup because the drag link is about 5-6" longer than the track bar. If they're perfectly parallel at stock ride height, they won't be at 4" of lift, and even if they're perfectly parallel at ride height for a 4" lift, the more squat or dive you get the less parallel they'll become, and the rate they diverge becomes worse with increasing lift height. You could get them perfectly parallel at the lifted ride height by lowering the frame side track bar mount, but that usually has a tradeoff with diff cover clearance/uptravel. A pitman arm with even less drop than stock could help at ride height but make it worse in dive/squat. There's not really an easy way to fully address it with stock width front axle so we just do the best we can and accept the rest.
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If steering box can't handle the 35" tires its because of the worn out worm gear and sector shaft. The steering boxes cannot be rebuilt. So however many miles were on the box before it was mounted to your jeep is unknown. Have someone do quick, short steering back and forth while you watch the box. My bet is you will see a little bit of movement where the big nut holds the pitman arm onto the steering box. Look at everything else too; TREs, steering box, trackbar, etc..any movement is going to need to be addressed.
So my thoughts are correct then... just ignore my little issue. It tracks straight, steers with 1-2 fingers, does not pull, wobble or vibrate...
I've never seen a teraflex swaybar in person. Only antirock. I do know guys run 35s on closer set wheels with a sway bar.lots of good examples here in the build thread forum.
Where is your inner bead? Man you need to take new pics of your jeep,for varietys sake!
OP
Thanks for your post. I've been looking at tire/wheel combos as I'm not loving the T/A KM3's. I'm thinking of going to a 17" wheel as more tires are available although I like the sidewalls on 15"'s. What would you recommend as a tire/wheel combo in size?
Thanks for the help! What size of tire are you running? My TF swaybar looks to be in the same position as yours but it definitely rubs...
OP
I just went for a drive and under hard acceleration it pulls to the left and when I decelerate (no brake) it pulls back to the right. Braking is straight with no pull although it takes awhile. Big brake kit eventually which will require going up in size on the wheels I believe.