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-   -   Vibration creeps in and won't go away (http://www.jeepgarage.org/f107/vibration-creeps-in-and-wont-go-away-67078.html)

Shaftcam 10-24-2013 04:12 PM

Vibration creeps in and won't go away
 
2012 Grand Cherokee Limited with 20" tires.

I'll try and be brief but I suffered through the Fortera vibration issues, did three road force balances and vibrations got worse. I finally ditched them about a month ago with 20" Falkens which immediately made the car more responsive at low and high speed. The ride is a little harsher but not by much but more than offset by the sharper handling. No more vibration at 115 km/hr or 70 MPH.

BUT........after about 40 minutes of sustained highway driving, a vibration will creep into the ride and then never go away for the rest of my drive. It sounds like it comes from the rear of the vehicle and is accompanied by a low grade rumble and a harsher ride. It feels like a tire issue but can that be??? For the first 40 minutes, I can go up and down through the speeds and there are no issues, vibrations, noises.

Braking is still smooth. There are about 1000 kms (600 miles) on the new tires. 21,000 kms on the vehicle. The new tires have not been road force balanced.

I'm at a loss to figure this out. I'd prefer to be able to go to the dealership with something for them to go with otherwise I guarantee they won't feel anything.

Any ideas? Thanks.

Dan

Peter_K 10-24-2013 07:45 PM

Re: Vibration creeps in and won't go away
 
By any chance is this a Hemi vehicle?

Otherwise, it could be that after that amount of high-speed driving your tire pressure has increased (due to tire heating) enough that a slight out-of-round condition is resulting in more road force variation on each tire rotation. The increase in pressure would also explain the harsher ride, especially with tires that are stiffer to begin with.

2012 Summit 10-24-2013 07:47 PM

Re: Vibration creeps in and won't go away
 
says "My Jeep: 2012 3.6L WK2"

Peter_K 10-24-2013 07:55 PM

Re: Vibration creeps in and won't go away
 
Ah, didn't see that up there.

In that case, I'd be pretty sure it's related to increasing tire pressure with long periods of high-speed driving.

Shaftcam 10-24-2013 08:43 PM

Thanks Peter. So, in that case, would a road force balance be useful?

mswlogo 10-24-2013 08:52 PM

Re: Vibration creeps in and won't go away
 
Could it possibly be Rear Load leveling Shocks?

I think normally with a trailer load they will stiffen up and try to lift the rear.

But if they are faulty and stiffen up they might transfer normal vibration into the frame so you feel it.

I thought I read there was a problem with load leveling shocks in earlier WK2 years.

Otherwise I agree with tire pressure. If you don't have TPMS display get out and check them manually once it starts vibrating.

Seems weird so many tire/balance issues. I never had tire balance issues on my old jeeps, even with cheapo tires. I have two sets for my 2014 and both are fine to 80 MPH.

Oh and I run my tires at 40 lbs and still no issues.

Peter_K 10-24-2013 08:57 PM

Quote:

Originally Posted by Shaftcam (Post 916744)
Thanks Peter. So, in that case, would a road force balance be useful?

That's where I'd start. After driving at high speed for a bit, your tire pressure could he 4-5psi higher than your normal cold inflation pressure. I'd have the shop inflate the tires up to that level, then do a full road-force balance (indexing the tires as necessary). Then when all of that is good, lower your pressure back to normal.

mswlogo 10-24-2013 09:02 PM

Re: Vibration creeps in and won't go away
 
Quote:

Originally Posted by Peter_K (Post 916752)
That's where I'd start. After driving at high speed for a bit, your tire pressure could he 4-5psi higher than your normal cold inflation pressure. I'd have the shop inflate the tires up to that level, then do a full road-force balance (indexing the tires as necessary). Then when all of that is good, lower your pressure back to normal.

Then his tire will be out of balance when cold (if it changes balance with 5 lbs delta).

Something isn't right.

Peter_K 10-24-2013 09:02 PM

Quote:

Originally Posted by mswlogo (Post 916750)
Could it possibly be Rear Load leveling Shocks? I think normally with a trailer load they will stiffen up and try to lift the rear. But if they are faulty and stiffen up they might transfer normal vibration into the frame so you feel it.

Certainly possible...but the timeframe would be random. This would be something to look at next after completely evaluating the tires.

Quote:

Seems weird so many tire/balance issues. I never had tire balance issues on my old jeeps, even with cheapo tires. I have two sets for my 2014 and both are fine to 80 MPH. Oh and I run my tires at 40 lbs and still no issues.
It's not all that strange when you consider that these vehicles are simply becoming more sensitive by design. Older jeeps also had solid axles...more unsprung weight. As such...more mass under the springs. Mass is the best way to dampen vibration harmonics.

Peter_K 10-24-2013 09:06 PM

Quote:

Originally Posted by mswlogo (Post 916753)
Then his tire will be out of balance when cold (if it changes balance with 5 lbs delta). Something isn't right.

Not true. Balance is balance...inflation pressure doesn't affect balance at all.

Higher tire pressures CAN exacerbate an out-of-round or tire carcass issue that doesn't show up at lower pressures (the tire is softer and the harmonics with relation to the suspension change)

Higher pressures can also cure a slight out-of-round condition as well (higher pressures rounding the tire out more).

mswlogo 10-24-2013 09:14 PM

Re: Vibration creeps in and won't go away
 
Quote:

Originally Posted by Peter_K (Post 916754)
Certainly possible...but the timeframe would be random. This would be something to look at next after completely evaluating the tires.



It's not all that strange when you consider that these vehicles are simply becoming more sensitive by design. Older jeeps also had solid axles...more unsprung weight. As such...more mass under the springs. Mass is the best way to dampen vibration harmonics.

Hmmm, not sure I buy that. I have had several independent suspension cars and never seen this many issues. No road force balance. Balance once for the life of the tire. Rotate when swapping snows regardless how many miles they go.

Maybe the rotors are out of balance? That would fit. Oh wait that would not explain the 40 minutes. I wonder if the rotor could get out of round or warp when hot. Creating a sideways vibration. If that was the case you should feel it in the breaks.

I'd swap tires front and back. Or lower tires 5lbs and/or raise tires 5lbs and see if anything changes. If nothing changes rebalancing at 5 lbs up won't solve anything. If anything does change (sounds in front) then it's tires. Then swap one side front to back. etc. etc.

Peter_K 10-24-2013 09:22 PM

Quote:

Originally Posted by mswlogo (Post 916761)
Hmmm, not sure I buy that. I have had several independent suspension cars and never seen this many issues. No road force balance. Balance once for the life of the tire. Rotate when swapping snows regardless how many miles they go.

You've been lucky then. I've seen plenty of these issues on lots of vehicles. There are some suspension dynamics that also come into play on larger IFS setups as well.

Quote:

Maybe the rotors are out of balance? That would fit. Oh wait that would not explain the 40 minutes. I wonder if the rotor could get out of round or warp when hot. Creating a sideways vibration. If that was the case you should feel it in the breaks. I'd swap tires front and back. Or lower tires 5lbs and/or raise tires 5lbs and see if anything changes. If nothing changes rebalancing at 5 lbs up won't solve anything. If anything does change (sounds in front) then it's tires. Then swap one side front to back. etc. etc.
Rebalancing alone at 5psi up won't solve anything--but checking road force at 5psi up could very well identify something. I've found quite a few issues that way.

I wouldn't move tires around until that's been looked at. Otherwise you're throwing more variables into the equation.


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