Porpoising? Cause?

[G-reg]

We are pulling our 30ft 2016 Coachmen Catalina (7700lb) with a 2013 F150 Supercrew short bed with 6.2L gas and 3.73 axle ratio. Using a Husky centerline TS wdh. Seems to be behaving very well. I see so many being told they should get a 3/4 ton but so far, not a waffle from the camper from side to side.

However, on occasion, there is some up and down response my wife says is like "someone tapping on the brakes". I'm assuming this is what is called porpoising.

Is my wdh out of adjustment(measurements look good)? Do I need airbags? What do I need to do to correct?



16 Coachmen Catalina 273dbs
13 Ford F-150 6.2/3.73 max tow

[trbomax]

You dont say how many miles on the truck or what you have for shocks on it,but the first thing i would do would put a set of Bilstien gas shocks on all 4 corners.The stock shocks were junk when they were new.

[G-reg]

The truck has 51k miles on it and they are indeed stock shocks.




16 Coachmen Catalina 273dbs
13 Ford F-150 6.2/3.73 max tow

[acadianbob]

We found that we had significantly less up and down motion at the rear of the truck by going from P Metric tires to LT tires. The LT's have a much stiffer sidewall resulting, IMO, in less flex.

[trbomax]

The Bilstiens are a little pricey but I will tell you that i put a set on my 2000 sd when it had about 1000 miles on it. 14 yrs and 200000 mi later I replaced them and the ones they took off still had a charge in them and most of the dampening left. LT tires are a must if towing also.

[asquared]

Best thing to see if your wdh is adjusted properly is a trip to the scales. Do 3 passes. First pass is truck only. You will have front axle on scale pad one and rear axle on scale pad two. Next weigh will be truck plus trailer without the wdh hooked up. The truck will be positioned as in first weigh and the trailer axles will be on scale pad three. Third weigh will be truck plus trailer with wdh hooked up.

Now look at your weights. First pass allows you to see the truck unloaded weights. You can calculate your available payload and adjusted towing capacity as well as what you have available on your rear axle using these weights..... gvwr - total truck weight = available payload. Gcwr - total truck weight = adjusted tow in capacity. Grader - rear axle weight = room available on rear axle.

Second pass allows you to calculate actual trailer weight and actual tongue weight. Total weight on pass 2 - total truck weight from pass 1 = actual trailer weight. Total of drive and steer axles from pass 2 - truck total weight from pass one = trailer tongue weight.

Third pass is used to help figure out how correctly your hitch is adjusted. You want your front axle as close yo unloaded weight as possible without going heavier.

The cat scales will charge $9-12 for first weigh and $1-3 for each reweigh in a 24 hrs period. Weighing is a pain but eliminates some of the mystery of the cause of your porpoising. When you get your tongue weight, see what percentage of the loaded tt weight it is. Ideal is 13-15% of loaded weight. If you are lighter than that, you need more tongue weight. This can be achieved by reorganizing your tt to put more weight in front of the axles. Once this is all situated and you still have the issue, then consider LT tires.

[G-reg]

Sounds wise. I will weigh this week. With regard to tires, I am still running the original Pirellis so am looking at replacing before winter. Would the Michelin LTX M/S2 - 275/55R20 113H be a good fit both for every day diving as well as towing on weekends? Any other recommendations?


16 Coachmen Catalina 273dbs
13 Ford F-150 6.2/3.73 max tow

[thebrakeman]

What is your actual TW, and what is your WDH rating.

I believe that running a WDH with spring-bars rated too close to the actual TW can also be a main contributor to porpoising. For example, if I have a 1000 lbs rated WDH, and my actual TW is 950 lbs, I would expect too much flex in the bars. When the road gets wavy, they will act too much like a "spring" and not enough like a "bar" to dampen that waviness. In that case, I would recommend a 1200 lbs WDH system.

My own TW is about 750lbs, and I went with the 1000 lb Equalizer. I'm glad they don't make an 800 lbs Equalizer, or I may have been tempted to go with that. My combination is very solid, even with a soft suspension, P-rated tires, and standard shocks.

Don't get me wrong, upgrading all of these things certainly will help. But I see no reason for anyone to run too close to their WDH rating. The extra cost and weight to go up another 200 lbs is pretty small, and you certainly would not be over-rated.

[G-reg]

Good point on the WDH. My hitch is a Husky Centerline TS with 800-1200lb rating.

The trailer is allegedly a 738lb hitch weight so I'm thinking that shouldn't be the source.


16 Coachmen Catalina 273dbs
13 Ford F-150 6.2/3.73 max tow

[Orion]

Id question that weight. My 832ikbs is listed at about that. However when I use a scale it read closer to 1,100 pounds🙀


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[asquared]

Originally Posted by G-reg

Sounds wise. I will weigh this week. With regard to tires, I am still running the original Pirellis so am looking at replacing before winter. Would the Michelin LTX M/S2 - 275/55R20 113H be a good fit both for every day diving as well as towing on weekends? Any other recommendations?


16 Coachmen Catalina 273dbs
13 Ford F-150 6.2/3.73 max tow

Those are very good tires and should give you good results but may not fix the porpoising issue.