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CWSWine's avatar
CWSWine
Explorer
Aug 12, 2013

Porpoising

I have a 2013 Ext Cab Chevy Diesel 2500HD and a 2014 Cougar 28SGS with Resse Hitch that I just brought home this weekend. The truck on both cement and asphalt is porpoising to the point it was making my wife sea sick. After arriving at the camp grounds I realized the dealer had filled the fresh water tanks over half full and they set all the way in back of trailer so I drained them. Is there anything else I should be looking at? Here is the way the 5th Wheel sits.

  • iawoody2's avatar
    iawoody2
    Explorer
    Aug 12, 2013
    Removing the water might help . Does your sefup sit level? Somtime you should find a CAT scale at a truck stop and get weights of total truck and trailer, rear axle, and front axle. Then just truck total, rear and front axles. You should have 20 to 23% of trailer weight as pin weight. I have 22% a ride is very good except on some of our finer roads.
  • CWSWine's avatar
    CWSWine
    Explorer
    Aug 12, 2013
    My setup is almost perfectly level. The rear of the trailer has two light chairs with a mid kitchen and TV that are over the wheels. We are not storing anything aft of the wheels and all the storage in the kitchen is about foot in front of the wheels. We are going to hook it up tomorrow and bring out on the road and see how it rides and see if I can find a scales that will work with us.
  • mdamerell's avatar
    mdamerell
    Explorer
    Aug 12, 2013
    Maybe it's an optical allusion but is your 5th wheel mounted correctly? It appears to be behind the rear axle instead of just before it.
  • hmknightnc's avatar
    hmknightnc
    Explorer
    Aug 12, 2013
    mdamerell wrote:
    Maybe it's an optical allusion but is your 5th wheel mounted correctly? It appears to be behind the rear axle instead of just before it.


    I was thinking the same thing. Go make sure your truck hitch is installed correctly. The picture makes it look like it is set to far back. The FW Pin should at least an 1 inch (and preferable more) in front of the axle.
  • ScottG's avatar
    ScottG
    Nomad
    Aug 12, 2013
    I had the same problem with my TT. Tried new Rancho shocks but they weren't any different from the stock parts. Then I installed Bilstein shocks and it completely stopped the porpoising.
  • CWSWine's avatar
    CWSWine
    Explorer
    Aug 12, 2013
    The hitch where the pin attaches in just forward of the center line of the rear wheels. I think what you are seeing is the max turn technology makes it look like it set back. The pin box on the trailer extends quite ways past the nose of the trailer.
  • IndyCamp's avatar
    IndyCamp
    Explorer
    Aug 12, 2013
    We had the same experience this weekend with our TT.

    We picked it up and the dealer had filled the fresh water tank 2/3 full without telling us. The water sloshing around caused some porpoising that we didn't expect. We drained the water at the campsite and didn't experience it on our way back.
  • CWSWine's avatar
    CWSWine
    Explorer
    Aug 12, 2013
    After we dump the fresh water it improved quite a bit. I may have explained it wrong, the movement is just back and forth not like when you cross over on bridge and get the up and down and back forth all in the same movement. This more jerking and it all the time and seems to increase going up hills but does not go away while on flat land or going down hills.

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