front shimmy at highway speeds, not tires

[jayson44]

my wife's JKU has a slight shimmy at speeds over 60 or so. her tires were really low so I just assumed that was the issue. but today we got brand new 35s installed and on the way home it shimmied again. I was hoping the new tires would solve but dang it, I guess not.

the shimmy is slight and it doesn't feel like a loose track bar. I'm gonna do a dry turn test later today to make sure, but I've had death wobble in my old TJ, so I know what that feels like. the wheel doesn't turn with the shimmy either...it's more like driving over a washboard road with really little washboards. could shocks do that? stabilizer? again, the steering wheel doesn't turn with the shimmy, it just shakes, so I don't think it's the stabilizer. but the Jeep is almost to 80k miles on the stock suspension. so I'm assuming it's a bushing somewhere.

it could also be a warped brake rotor...it's been about 35k since I replaced the brake pads and rotors. there's no squealing and the pads look ok, but I'm thinking I'll do that since they're gonna need it anyways. would a rotor make a shimmy like that? it doesn't shake when braking.

any other ideas I should check?

J.

[Brian]

Front end alignment?

[Jim]

left/right shimmy in the steering wheel - rotors would be high on my list

If you lightly press on the brake pedal when the shimmy is happening - do you feel any slight pulsing?

[Tom]

Tires out of balance or defective e.g. radial belts misaligned in the tires.

[jayson44]

Front end alignment?

hmm...duh Jay! yeah I think that will be on the list. haven't gotten it aligned since we put the lift on it almost 4 years ago.


left/right shimmy in the steering wheel - rotors would be high on my list

If you lightly press on the brake pedal when the shimmy is happening - do you feel any slight pulsing?

no pulsing and the steering wheel doesn't actually turn at all. it shakes the whole front of the jeep...you can feel it in the dash and everything.



Tires out of balance or defective e.g. radial belts misaligned in the tires.

Brand new tires today. still shakes, and it's not any different than it was with the balding KO2s.

J.

[Tom]

Tires out of balance or defective e.g. radial belts misaligned in the tires.
I have had this this happen on brand new tires that's why I brought it up.

[jayson44]

I have had this this happen on brand new tires that's why I brought it up.

Yeah, I would think these being bigger would produce a much bigger shake if that were the oddball case. but it feels the exact same.

J.

[Jim]

Correct me if I'm wrong - you had a shake on the old tire set. You changed to new tires - that are bigger (yes?).

Is the frequency of the shake in line with the rotational frequency of the tires or is the frequency of the shake about 3.5x the frequency of the tire rotation? Is your front driveshaft spinning when the shake happens? ala - is it an off-balance front driveshaft?

[Java]

Sounds like an alignment is in order, but with your mileage and tire size its a good possibility that you're wearing out your tierod and or draglink ends, which are cheap and easy to replace before getting it aligned. Might just be time anyway, cheap insurance.

[jayson44]

Correct me if I'm wrong - you had a shake on the old tire set. You changed to new tires - that are bigger (yes?).

Is the frequency of the shake in line with the rotational frequency of the tires or is the frequency of the shake about 3.5x the frequency of the tire rotation? Is your front driveshaft spinning when the shake happens? ala - is it an off-balance front driveshaft?

Yes to your questions, Jim. shake on the old tires, pretty bad really, at speeds over 60. and the new tires are 35s instead of 33s.

as for the driveshaft, that's actually not a bad thought. we rarely wheel Kayla's Jeep, but we have so there's the possibility that we hit it on something. we did hit up Pickle Gulch just before Father's Day. maybe a scrape put a dent in it? I'll crawl under there and check. I can always disconnect it and see if it goes away, too. thanks!

J.

[Spieg]

When you had the new tires mounted, did they inspect the wheels to be sure none are bent?

[jayson44]

When you had the new tires mounted, did they inspect the wheels to be sure none are bent?

I didn't ask them specifically to do that, but I would assume that if the wheels were bent for whatever reason, they would have let me know.

J.

[ColoJeeper]

Change the location of the tires and see if the shimmy seems to change. Did with mine and ended up being a bent wheel.