Okay, so I recently got 35" BFG KO2s off of craigslist and threw them on my JK. I started to get weird bumpsteer; my Jeep started to sway and pull in every which direction but oddly it doesn't pull when braking. I went ahead and bought a dual steering stabilizer and this seemed to help immensely until a week later. I tightened up the steering stabilizer a little more thinking that was what was wrong and it helped a little. This past weekend I installed a 2.5" BB and the swaying has gotten pretty bad. It's like I'm driving in a wind tunnel and I'm constantly fighting my Jeep to go straight. I looked up what this could be and I read about bumpsteer being an out-of-parallel trackbar and drag link. I peeked under my Jeep to find that my drag link and trackbar are still parallel to each other. Could this be bad tires or am I missing something here?

 

What pressure is in the tires.

 

Caster angle ?

 

what year jeep, how many miles, are tires balanced?
did you buy rims and tires? you may need hub centric rings.

 

My 2012 did the exact same thing so I took it in had it aligned and the problem disappeared.

 

It's a 2015. It has stock rims and BFG KO's that I bought off Craigslist. They are all at 30 psi now but I have tried 35 and 28 and 30 psi seems to be my comfortable pressure. Tires have been balanced twice. Jeep has less than 20k miles. I'm leaning toward alignment since that's really the only thing left but I don't understand why it would need an alignment. Also, I just noticed the back tires are wearing unevenly. They are starting to wear on the outside only. I'm planning on getting tires within the next couple months, though.

 

I also recommend the alignment. For the uneven tire wear it sounds like your tire pressure is too low. If you have access to a decent flat surface you should do a chalk test. If you don't know that is where you draw a line across the tires tread laterally and drive over it a couple times then check the chalk. If it only wears on the edges you pressure is to low, center area but not the edges to high. Do that until you get even chalk wear on all four tires and you'll know what your optimal tire pressure is.

 

Used tires. Previous owner did not rotate.

You said that you had them balanced. Have you rotated them to see if that helps?

The bumpsteer started 'after' putting on the used tires. Why would an alignment fix a bad set of tires? You put on a spacer lift, so I will assume it has no adjustable components? The only thing the alignment shop will do is adjust the Toe and recenter the steering wheel. They can not adjust the caster, they can not adjust the camber. (unless you buy more parts). So my suggestion would be, instead of paying for an alignment, find a shop that does free checks. Just have them throw it on the rack and print the specs, then if you have any questions, post those specs and ask.

 

The Jeep is on the lift now, NTB is going to check the alignment check for free. It started a bit after putting the used tires on so that's why I'm curious. And they weren't unevenly worn when I bought them. I will post the results of the alignment check.

 

The alignment is within specs.