Porpoising at highway speeds

OP
OP

Ron ap Rhys

Active Member
First Name
Ron
Joined
Jun 5, 2020
Messages
27
Reaction score
7
Location
Mordor
Vehicle(s)
2020 JLU Rubicon, Granite Crystal Metallic
Thanks to everyone for the responses and suggestions. I did reduce the tire pressure from 42 to 34psi. I also set the shocks to Sport mode. Did the test drive, still porpoised. Flipped the shocks back to soft mode - same damn thing. Was at my wits end with this one. Chatted with a buddy of mine who's a suspension engineer for Fox and he suggested I try a different highway, just in case.

That worked.

The deal here is that I-94, which is right next to my place, is concrete with expansion joints. It normally feels smooth, but with the JLUR wheelbase and this new set up, it's perfect for creating this condition. I jumped on an asphalt highway and the Jeep rides nice and smooth. Given that, it's got to be the road surface itself.

That makes me feel much better as we're headed out to Utah here in a few weeks and I would've hated to have to deal with that for the over 4k miles we'll be driving. Hell, I would've put the stock suspension back in first.
Advertisement

 

2003hummerh2

Member
Joined
Jan 24, 2019
Messages
20
Reaction score
22
Location
Texas
Vehicle(s)
2018 Jeep Wrangler JL
I would check your fuses. My fuses were a few mm out and once I pushed them all back in, it fixed my Jeeps horrid steering and gave me my low end torque back.
 

Ehmsea

Well-Known Member
First Name
Aaron
Joined
Jul 3, 2018
Messages
96
Reaction score
160
Location
Perrysburg, OH
Vehicle(s)
2018 JLUR, 13 Camaro SS, 04 Pontiac GP
Occupation
RF Engineer
he suggested I try a different highway, just in case.

That worked.

The deal here is that I-94, which is right next to my place, is concrete with expansion joints. It normally feels smooth, but with the JLUR wheelbase and this new set up, it's perfect for creating this condition. I jumped on an asphalt highway and the Jeep rides nice and smooth. Given that, it's got to be the road surface itself.
He beat me to it...
I live in NW Ohio and every time I go North into MI on I-75 or US-23 I get this effect. About 30 minutes in and I feel like I'm getting carsick. It happens in both my Jeep and Camaro. You can change your speed, that will change the frequency of the Porpoising. Try going 65 instead of 85 (Its a Michigan thing), but Stay to the right...;)

Every time we drive into MI, I ask my wife "They pay taxes here, right?"
 
OP
OP

Ron ap Rhys

Active Member
First Name
Ron
Joined
Jun 5, 2020
Messages
27
Reaction score
7
Location
Mordor
Vehicle(s)
2020 JLU Rubicon, Granite Crystal Metallic
I'm hella familiar with the crap roads here - and I've been referring to this state as Mordor since I moved here. My wife has a 335i that had cast rims and rubber band tires. Handled great - but we were paying $200 every month to have a rim repaired. Finally broke down and bought forged rims to help prevent that.

What's going to be fun is heading out to CO and UT if that happens. We'll be loaded down, so hopefully that stops the worst of it.
 

Ruby Mike

Well-Known Member
First Name
Michael
Joined
Apr 13, 2020
Messages
478
Reaction score
800
Location
Southern California
Vehicle(s)
2020 jeep wrangler diesel
Want crappy freeways? Come to California. Oh yeah, we pay the highest fuel tax in the country.
 
OP
OP

Ron ap Rhys

Active Member
First Name
Ron
Joined
Jun 5, 2020
Messages
27
Reaction score
7
Location
Mordor
Vehicle(s)
2020 JLU Rubicon, Granite Crystal Metallic
Certainly not from CA - and I'm pretty sure Mordor here gets consistently voted into the top worst road states year after year. Hell, that's why we've got the current governor - she promised to fix the roads (and has been mostly stymied on that front, too).
 
Advertisement

Smart Stop Start
 
Advertisement
Top