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Old 08-24-2015, 09:47 AM
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New 35's result in bump steer?

I bought a set of General Grabber Red Letter 35x12.50x17 tires & mounted to brand new Pro Comp La Paz 17x8.5 wheels. 4wd.com shipped them mounted & balanced. They ride quite & straight down the road. I have a Jeep Wrangler, 2 door X with a 2.5" Pro Comp Lift, Rubicon Express lower control arms & adj track bar. QUESTION is.. I am getting a lot of bump steer and nearly crashed from hydroplaning in an inch of water @ 40mph. I replaced a set of worn 35x12.5x17 Pro Comp Xterrain's that DID not have the same problem. Can anyone offer thoughts & suggestions? I've tried tire pressures from 30-40 and seem to get the same result.

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Old 08-24-2015, 09:49 AM
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I should add... I've put 1500 miles on them & no change.

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Old 08-24-2015, 09:56 AM   #3
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Chalk test the tires. You should be around 26-28 psi i bet.

Did you remove the factory rotor clips ?
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Old 08-24-2015, 10:41 AM   #4
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bumpsteer is a geometry thing . The bumpsteer name is kind of misleading . Kind of why some think a steering stabilizer corrects it
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Old 08-24-2015, 12:49 PM   #5
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Yep, always check geometry first!

While alot of folks don't run them...I still like a slightly beefier SS when running larger tires, reduces feedback through the steering wheel in rough conditions.

Usually bumpsteer is caused by the trackbar and draglink no longer being parallel (after lifting), which is why most lifts above 2.5 offer high-steer kits to correct that issue.

QTec has a nice write up on the issue. This is a TJ, but the components (and condition) in question are similar on a JK.

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Old 08-25-2015, 11:11 AM
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Hey guys...thanks for your thoughts!

I do have a dual steering stabilizer to even out the trail feedback. Also added an Rubicon Express adjustable track and front lower control arms after I did the Pro Comp 2.5" - I was amazed at the scary steering with only lifting 2.5" (actual lift was 2.75").

I'm awaiting an answer from General Tire...I'll leave their response.
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Old 09-22-2015, 09:56 AM
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Thanks kjeeper10... You & General Tire agreed that 26psi is the right number. The skittery feedback is 90% improved with the lower air pressure. Highway & newer roads are literally prefect with the grabbers - quiet & straight. Secondary roads that are bumpy & crowned are still a two hands on wheel situation. Thanks again!
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Old 10-08-2015, 10:57 AM   #9
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Hey guys,

I've noticed the steering wheel on my 2-door Rubicon also started doing the rumba, ocassionally, since the dealer installed the Mopar 2" Lift with Fox Shocks, when I stomp on the brakes at low to moderate speeds on bumpy or uneven surfaces.

I am running 35x12.5 General Grabber Red Letter tires as well.

Thoughts? Suggestions?

Thanks,

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Old 10-08-2015, 11:29 AM   #10
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Quote:
Originally Posted by aldo90731 View Post
Hey guys, I've noticed the steering wheel on my 2-door Rubicon also started doing the rumba, ocassionally, since the dealer installed the Mopar 2" Lift with Fox Shocks, when I stomp on the brakes at low to moderate speeds on bumpy or uneven surfaces. I am running 35x12.5 General Grabber Red Letter tires as well. Thoughts? Suggestions? Thanks, Aldo
Sounds like a Common tready tire issue.
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Old 10-08-2015, 12:29 PM   #11
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Thanks for the link!

So based on this:

Steering wheel jerks left/right over bumps: This is known as bumpsteer. Bumpsteer is caused when the track bar and drag link angles are too steep, lengths, and geometry are off. As you go over a bump with one tire, the jeep jerks and sometimes will steer itself. Bumpy roads can be scary with a good case of bumpsteer. Bumpsteer is really is not a issue until up around 4", but the fix is a steering correction kit Raising the track bar & flipping the drag link is the ideal way to fix bumpsteer at higher lift heights -returning the geometry back to normal. Some kits do this similar using a drop pitman arm. I do not recommend using a DPA, it actually puts more stress the steering box. lowering the track bar reduces front roll center. one of the other benefits of a raised TB bracket is roll center correction.

Doesn't sound like this is something my Jeep dealer would be able to fix --which would have been ideal since they installed the lift.
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Old 10-08-2015, 01:30 PM   #12
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A friend had similar symptoms with a bad tie rod end.

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