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Discussion Starter #1
I beleive I am experiencing slight bump steer issues.

I installed a 2.5" rock krawler lift this past weekend. I ran the stock Willy's wheels and tires for a couple days and didn't experience any issues. I put on 35" Nitto Ridge Grapplers two days ago and have noticed an occasional desire for the jeep to pull fairly hard one way or the other when going over a decent bump.

are my new, taller tires just exacerbating the issue enough that I notice it now and did not previously? or are the causing an issue I can't think of?

I will be doing a chalk test tonight, alignment soon, etc, just wanted to get a feel for what you guys/girls think

thanks!

pic for attention
 

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Larger tires tend to follow road imperfections more. It may be that is all it is.
Typically with tires that big people usually run air pressure in the upper 20's, like 28 psi. Too much air pressure may make it drive poorly.
 

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Discussion Starter #3
Larger tires tend to follow road imperfections more. It may be that is all it is.
Typically with tires that big people usually run air pressure in the upper 20's, like 28 psi. Too much air pressure may make it drive poorly.
good point, they were at 36 or so from the shop, I lowered to 30 and will lower them again to see if it improves.

This is my first vehicle with tires this large so that could be it and I could be overreacting. It's definitely not approaching the horror stories I have read about being fearful of driving it on the highway and whatnot.

No lack of road imperfections on my commute either.
 

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Just make sure your track bar and drag link are pretty close to parallel, if not you will have some bump steer. But the bigger tires do tend to follow bumps in the road, especially if they are overinflated. For E rated tires, 26-28psi is usually good.
 

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good point, they were at 36 or so from the shop, I lowered to 30 and will lower them again to see if it improves.

This is my first vehicle with tires this large so that could be it and I could be overreacting. It's definitely not approaching the horror stories I have read about being fearful of driving it on the highway and whatnot.

No lack of road imperfections on my commute either.
FWIIW I run Nitto Trails (35x12.5s) and I feel grabbing on the highway at times and when braking. Normally behavior for mine. I would not trade them. :)
 

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Discussion Starter #6
FWIIW I run Nitto Trails (35x12.5s) and I feel grabbing on the highway at times and when braking. Normally behavior for mine. I would not trade them. :)
I felt a little grab when on my way to lunch, this is seeming more likely than bump steer at this point. definitely love the ride they give other than not being used to that grabbing

thanks everyone!
 

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I noticed when upgrading to my 315's from 255's, the 315 KO2's definitely grab road imperfections more-so than the 255's. I had lowered the PSI to ~30 from 34 on my KO2's and it definitely drives a good bit better. I still get some steering wobble when going over some bumps so I believe my ball joints or unit bearings might be on their way out. 33k mi and just started running the 315's a few weeks ago.
 

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I had the exact same problem. When the jeep was stock and new it drove well. Even handled just as well when I did a 3" lift (with stock wheels). As soon as I went to 315's, I started to feel what I THOUGHT was bump steer.


Did some research and it turns out to be a phenomenon called TRAMLINING. It's pretty common with larger/wider tires.


Tramlining is the tendency of a vehicle's wheels to follow the contours in the surface upon which it runs. The term comes from the tendency of a car's wheels to follow the normally recessed rails of street trams, without driver input in the same way that the train does. The same effect is sometimes called Nibbling.
Tramlining can usually be blamed on tires, and its incidence depends greatly on the model of tire and its state of wear. Although not normally dangerous, at very high speeds it can become a source of instability.
Vehicles with large and wide low profile tires are more prone to the effects as well as vehicles which have wheels fitted that are larger than the manufacturers recommendation or have reinforced sidewalls. People who are relatively inexperienced with driving with this tendency will feel that they have to make continual course corrections and it is very easy to overcompensate the steering, which could potentially lead to veering off the road especially if the road is a narrow track/country road.
The effects of tramlining can be eased by subjecting the vehicle to an inspection and calibration of the wheels (i.e. a full geometry check) or replacing the tires with non-reinforced (soft sidewall) tires.
I played around and eventually removed the sway bar and that seemed to be a lot better. (Some people don't like that idea and think it's dangerous. I don't). The tramlining is almost unnoticeable now without the sway bar.


My personal opinion is that when you do a lift, heavier springs/shocks wider tires... yadda yadda, you reduce the need for such a heavy sway bar and keeping something as heavy on causes issues. Now I feel completely comfortable with no sway bar. The jeep is now driveable with one, where it wasn't with the tramlining on bumpy roads, but if you don't then you should experiment with a sway bar flex kit and see if that helps the tramlining. They will add some flex to the sway bar and in effect, make it appear as a lighter bar without completely removing it. I confess though... I have not tried them. I kind of like no sway bar.


https://www.quadratec.com/products/16160_0007_14.htm
 

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Discussion Starter #9
good info everyone.
I dropped pressure down to 28psi and loosened all the CA's and lift parts and retightened them and the sensation is much better, I still get occasional grabbing/trammeling but nothing serious and it definitely is not bump steer which is good
 
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