Bouncing Trailer

[jorboy]

Hello Fellow RVers- This forum has helped answer so many questions that every time I take my trailer out my confidence as a newbie grows. I do however need some more advise. During a recent trip I encountered a less than smooth highway which in turn caused my trailer to bounce. Just wondering if I could eliminate such bounching if I either put better shock absorbers on my truck or trailer or do I need to perhaps do change my truck's springs? As always I appreciate all advise!

 

[Jammer]

Jorboy the bouncing or porpoising of a trailer can have many causes and is nearly impossible to eliminate completely.

If the shocks in the tow vehicle are shot that will certainly contribute to the problem.

In many cases much of the problem is that the WD bars aren't tight enough.  Especially for larger trailers most people don't realize how much tension is needed.  It should be enough to restore the front axle weight on the truck to what it is without the trailer.  You can go to a place with truck scales and experiment, they will usually give you free or reduced cost re-weighs if you want to try stuff in the parking lot or unhitch.

 

[WeatherWunder]

I would start with the WD hitch.  I had the same issue a few years ago, and like Jammer said, I did not realize how much tension it really took.

 

[Carl L]

Hello Fellow RVers- This forum has helped answer so many questions that every time I take my trailer out my confidence as a newbie grows. I do however need some more advise. During a recent trip I encountered a less than smooth highway which in turn caused my trailer to bounce. Just wondering if I could eliminate such bounching if I either put better shock absorbers on my truck or trailer or do I need to perhaps do change my truck's springs? As always I appreciate all advise!

If the bouncing is taking place on freeways, you may be encountering freeway porpoising.  This is caused by a freeway surface getting regular wave-like undulations due to wear over the years.  Concrete surfaced highways seem to be the main offenders.  If the bouncing stops when you move onto a new or asphalt surface, then that is the problem. 

If that is the case, there is nothing much you can do except slow down and pray for better surface.  Shocks on the trailer may help if you do not have them already  -- many trailers do not.  I would not tinker with the adjustment of your WD hitch.  If yours is correctly adjusted according to the procedure outlined in our library, then do not fuss with it further  -- over-adjusting could put your rig into excessive understeer (plowing on turns).

 

[WeatherWunder]

Good Point Carl L.  What I meant was to be sure it was adjusted properly.  I did not explain myself very well.  Sorry!

 

[jorboy]

Thank you Carl- I think you hit on something I should have mentioned in my post. The bouncing or porpoising only seems to occur on concrete freeways.  Whenever it occurs I slow down which does seem to make the porpoising less severe.

 

[wgb1]

Not sure why concrete roads would cause freeway porpoising unless when the road was constructed, the pavement joints are lower or higher than the center of the slab. I just returned from Galveston last weekend and was on an elevated freeway near downtown Houston. Basically, it was a long, long bridge and the concrete prestressed beams obviously had a little too much camber (the driving surface was like this^^^^^^^- of course that is exaggerated). I was porpoising like crazy which I never do. I suppose the joints were spaced at exactly the right length for the spread between the axles of my truck and trailer.

 

[Carl L]

Not sure why concrete roads would cause freeway porpoising unless when the road was constructed, the pavement joints are lower or higher than the center of the slab. I just returned from Galveston last weekend and was on an elevated freeway near downtown Houston. Basically, it was a long, long bridge and the concrete prestressed beams obviously had a little too much camber (the driving surface was like this^^^^^^^- of course that is exaggerated). I was porpoising like crazy which I never do. I suppose the joints were spaced at exactly the right length for the spread between the axles of my truck and trailer.

Exactly.

 

[lavarock1210]

Low tongue weight?  Have you weighed the system?  High nose towing can also cause the problem with low end tongue weights.

 

[Gary RV_Wizard]

Is the trailer bouncing or the tow vehicle?  A bouncing trailer needs shocks on the trailer (few trailers come factory equipped with shocks).  If the trailer is jerking the tow vehicle around as it bounces, then you may have insufficient tongue weight ( should be at least 10% of the trailer actual weight) or improperly adjusted WD hitch or poor tow vehicle suspension. Or a combination of those.

 

[rats1955]

Jorboy-  What do you have for a tow vehicle and what are you towing?  A smaller tow vehicle has a tendency to be influenced by a heavy trailer while moving.  Causing a very jerky and bumpy ride. My father and I would pull the same trailer with different pickups.  The ride was much more comfortable with my heavier pickup.  Another idea is to see if the trailer it self is bouncing a lot.  Some shock absorbers would help that situation.  I have shocks on my most current 5th wheel.  They made quite a difference in ride quality.

 

[fastrak100]

I am pety sure that my rig is set up to spec, but I still get the porpoising. A deep long term study of concrete sections shows that different sections of road have different lengths of concrete section. So, the extent of the porpoising will be determined by your rig length, at some stage you will find (in the scientific sense) the 'perfect wavelength' and with the harmonic motion your rig will bounce higher and higher and higher. (And your partner will sceam louder and lounder and lounder)I found the circular round Birmingham Alabama, the I10 east of New Orleans and the Lake Ponchatrain causeway to the North of New Orleans to be particularly viscious to my rig.
Now my learned friends! As to a solution please give me your wise thoughts about the use of Air Bags. Are they worth the cash? both for a generally smoother ride under load and a solution for porpoising.

 

[jorboy]

Thanks to everyone for replying to my request for information regarding trailer bouncing. The only time I encountered the porpoising occurred on a recent trip to Arkansas. Since it was such an isolated incident, I believe Carl's explanation makes a lot of sense. I always load my trailer the same way so I don't think it was a matter of not having proper tongue weight. Also I never come close to reaching my cargo weight limits. The truck was bouncing and not so much the trailer so I'm not sure shocks on my trailer will help that much. I guess I just need to be mindful of slowing down should I encounter this again, which is what i did when I first experienced the bouncing. Again I really appreciate all the feedback I received for my questions. Everyone's replys gave me food for thought which is what makes this forum so great!

 

[Stewie Griffin]

Jorboy, do you have a fifth wheel or a TT?  Lots of posts suggest adjusting the Weight distribution hitch but that would be if you have a travel trailer, your original post indicated you have a fiver though. 
I had a lot of trailer bounce on my older TT but the only time it happens with my Fiver is when I get on concrete or asphalt that is wavy or the concrete joints are aligned perfectly with my trucks wheelbase.  As was said earlier, shocks would be a good idea if you don't have them on your trailer, they could really reduce the bouncing.  I replaced my fivers axles, it has cambered axles from the factory and were bent when I bought the trailer but the only axles we could find were much beefier straight axles, I get more bounce but I like the stoutness of the axles, I will be putting shocks on to help reduce the bounce.  Good luck.