Forum Discussion

Explorer

Sep 03, 2013

Odd question on trailer pitching

Hi all-
I don't normally post here, but I've got a nagging question about trailering that I haven't been able to find anywhere. I found out I wasn't the only person dealing with this. I had a person going from a 1/2 ton to a 3/4 ton to try to eliminate it.
We both checked hitch head angle, drawbar height, different WD Hitches, leveling with the truck and adjusting chain links on the WD hitch. It only happens on concrete roadways. The nose of the truck starts to bob up and down. the truck trailer seem to see-saw. It seems like the truck and trailer are doing an 'inchworm' move. My trailer/ hitch guy has heard of it, but no answer. Any help or thoughts here? I promised my friend I'd check into on here. Advise or thoughts are greatly appreciated. thank you!

15 Replies

azdryheat
Explorer
Sep 03, 2013
My fifth wheel will do the same thing. Airbags and better shocks on the truck helped a lot.
classicdude
Explorer
Sep 03, 2013
Mine does this a little bit on certain sections of roads, but without doubt it is easily controllable with a properly adjusted WD system.
SDcampowneroper
Explorer
Sep 03, 2013
What you are experincing is known as 'porpoising' It is a harmonic action caused by length of pavement expansion joints or arcing in prefabricated bridge sections in relation to your TV axle to Trailer axles.
When you come across such roads, simply adjust your speed faster or slower to negate the harmonic effects. You cannot get rid of that affect by any adjustment other than speed.
whiteeye42
Explorer
Sep 03, 2013
it is caused by the cut lines in the highway because they are to close together
old_guy
Explorer
Sep 03, 2013
hitch out of adjustment. you don't have enough weight on the front axle. try taking it up on link on the chain and try it again. it is called porpoising, look it up and it might even be in the FAQ's section on this page. or look it up on u tube under trailer porpoising.