Porpoising at highway speeds

Ron ap Rhys

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I've just installed a Teraflax ST2 2.5" lift with the Falcon 3.3 shocks on my 2020 JLUR - it's got under 2K miles and hasn't been wheeled yet (though I do drive on MI roads, which is kind of similar to wheeling). Lift went in without any real problems and I actually ended up with 3" of lift. When I went for my test ride, I noticed the Jeep was porpoising a bit at highway speeds and the steering wheel was cocked a bit. Took her in an had an alignment done and I'm still getting the porpoising.

Anyone else have similar problems? Any thoughts on solutions?

I did search on the subject, but nothing seemed to come up.
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Ron ap Rhys

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What exactly is porpoising?
Porpoising is a back and forth rocking motion - it's not side to side, but front to back. Kind of like a porpoise diving in and out of the water. It's pretty frequent - a couple times a second.
 

Hayseed_JLUR

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Are you sure it is not a dolphin?

Sorry, but the first thing that popped into my mind was Kanye swimming in the ocean at the end of the Fishsticks episode.

ETA: I am seeking help as we speak...
 
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Ron ap Rhys

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ETA: I am seeking help as we speak...
Thanks - I did talk to Teraflex about it yesterday (prior to the alignment) and they hadn't ever heard of this problem before. The only thing I've found online is stuff about drag cars (maybe useful) or vehicles being towed behind RVs (not useful).

The drag car solution was to stiffen up the shocks - since these are the adjustables, I need to make sure I'm on the firmest setting. Maybe that'll help, but I'm certainly open to other answers.
 

Fsttanks

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I've just installed a Teraflax ST2 2.5" lift with the Falcon 3.3 shocks on my 2020 JLUR - it's got under 2K miles and hasn't been wheeled yet (though I do drive on MI roads, which is kind of similar to wheeling). Lift went in without any real problems and I actually ended up with 3" of lift. When I went for my test ride, I noticed the Jeep was porpoising a bit at highway speeds and the steering wheel was cocked a bit. Took her in an had an alignment done and I'm still getting the porpoising.

Anyone else have similar problems? Any thoughts on solutions?

I did search on the subject, but nothing seemed to come up.
What is your tire pressure set at? New heavier springs and shocks will often require a change to your tire PSI. To high and you can see issues like you described.
Also if memory serves the 3.3 are adjustable so check the settings on your shocks. These may need to be adjusted up or down.
 

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Ron ap Rhys

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What is your tire pressure set at? New heavier springs and shocks will often require a change to your tire PSI. To high and you can see issues like you described.
Also if memory serves the 3.3 are adjustable so check the settings on your shocks. These may need to be adjusted up or down.
I'm set at 42 in the rear, which is what it came with from the factory. I've thought about dropping that down to 36-38, but just haven't done it yet. I'm going to check the shock settings after my next round of conference calls (yay corporate work from home life).
 

Fsttanks

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I'm set at 42 in the rear, which is what it came with from the factory. I've thought about dropping that down to 36-38, but just haven't done it yet. I'm going to check the shock settings after my next round of conference calls (yay corporate work from home life).
Reading that you are still on stock 33s? Drop the PSI to under 35 “cold”. I dropped mine and it made a world of different in overall ride. I run my 315 KO2s at 32 psi “cold” and the road feel / handling is much nicer then the stock 33s at 42.
 

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I've just installed a Teraflax ST2 2.5" lift with the Falcon 3.3 shocks on my 2020 JLUR - it's got under 2K miles and hasn't been wheeled yet (though I do drive on MI roads, which is kind of similar to wheeling). Lift went in without any real problems and I actually ended up with 3" of lift. When I went for my test ride, I noticed the Jeep was porpoising a bit at highway speeds and the steering wheel was cocked a bit. Took her in an had an alignment done and I'm still getting the porpoising.

Anyone else have similar problems? Any thoughts on solutions?

I did search on the subject, but nothing seemed to come up.
My guess is tire pressure, drop to 32 warmed up and try it.
 
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Ron ap Rhys

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I've adjusted the shocks to the firm setting - that may help a bit as it should help prevent some of the rebounding. I'll do the pressure lowering later, too - I've got to do some running around this evening anyway, so that'll give me a perfect test.
 

WagzDad

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Tire pressure is probably aggravating the shock rebound issue.
The last stretch of I55 is elevated before it ends at I10. The 20 miles are notorious for causing medium wheelbase pickups to porpoise, even new. When not carrying a load or pulling a trailer I have found dropping my tire pressure from 36 to 32 reduced the bounce. YMMV
 
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