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Old 06-06-2023, 06:00 PM   #1
Berdan
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Just another porpoising thread

Driving down 101 in Washington this last weekend there were a number of places where the road had some pretty wavy sections that caused significant porpoising on my TV/Trailer. Under most road conditions I don't experience this but by the time you realize you hit that weird stretch of road your already there. My rear end does not feel like it is bottoming out during porpoising but the ride is pretty exciting. Also wondering how long my shocks will last without additional mitigation.

Looking for advice on the most practical way to damp out the porpoising more quickly, or even to prevent it without breaking the bank.

My TV is a 2020 Silverado LT Crew Cab short bed 4x4 with standard towing package (not Max Towing)and my TT is a 2015 Cougar RBWIE with GVWR of 7200 pounds. Since these threads usually start with people asking "are you sure you have enough TV, is the WDH adjusted properly, and is the hitch weight 10-15% of trailer weight", I will refer you to my weight statistics at this post to get past that quickly:

https://www.keystoneforums.com/forum...ad.php?t=50227

Also included is a picture of my TV with trailer hitched up on level ground so you can see that the WDH is reasonably well adjusted.

So the discussions I have seen in previous posts are:

1) Stiffer shocks/springs maybe air shocks. (The GM max tow package has heavier duty shocks and springs)

2) Jounce style springs (Timbren, etc.)

3) Air Bags

4) Other?

I have to say it seems somewhat drastic to put 5000 lb capactiy air bags on a 1/2 ton rear end with a 950 lb. upper hitch weight limit, but I am interested in what others experience is with this weight range TT and TV.

Thanks in advance,

Brien
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Old 06-06-2023, 07:04 PM   #2
sourdough
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Your spreadsheet in the link seems to only list online specs vs a scale weight. A 1920 payload for a 1500 is pretty stout particularly without a towing package of any kind. Those things cast some doubt on the numbers. It's a trap too many fall into.

IMO you have a grocery getter 1/2 ton truck (I've owned them and a 3.23 ration is NOT for towing) that was meant for some 2x4s and not towing an RV. Be that as it may you have what you have. With that kind of truck you have 1) light weight springs, 2) probably lighter duty shocks and 3) no anti sway bar (truck) of any kind for a few things.
That kind of truck with that RV poses some issues that requires corrective action...sometimes expensive.

The soft suspension will let the truck porpoise and actually exacerbate any push/pull, up/down motions. You can't fix it unless you get a truck meant to tow. You can try to minimize the effects; 1) replace tires with LT tires, 2) replace shocks with HD shocks (I used Bilstein), 3) install air bags (I used AirLift 1000), install a HD rear anti sway bar (I used Hellwig) and 4) make sure all tires (truck and RV) are aired to sidewall max. If you are using OE tires on the trailer you can upgrade one load range to make the tires stiffer.

You don't say what kind of WD hitch you have but when your truck is at a disadvantage you need something that is top line, not just a "weight distribution" hitch and it needs to be set up to spec.
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Old 06-06-2023, 08:56 PM   #3
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Danny,

Thanks for the response. The ratings come from the Trailering Information Sticker on the Drivers Side for my specific VIN build configuration. I am not sure where to find better numbers but I think your point is that you are skeptical of the credibility of the published specifications with regard to towing.

Upgrading to LT tires is in my plans and okay on recommending HD shocks and Airlift 1000 (seems more reasonable than 5000s). I already upgraded my TT tires to Carlisle ST E-rated tires.

WDH is a Reese PRO Series 10000/1000 hitch with friction sway control bar. It is set up per the Reese specs.
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Old 06-07-2023, 03:50 AM   #4
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I can honestly say. I had the exact frame of mind. I didn't go off model specs, I went off my exact truck specs and capacities. It had tow package etc. All the math worked out just fine. What you have to realize is math is just that, math rated for averages. Using those math equations my 1/2 ton truck "should" have been just fine with my TT. The cat scale showed differently. The way the TT is set up (arranged) can greatly affect those averages. I found in fact that I was right at my payload capacity and over my rear axle capacity. Things just sat differently than the math said they should. I had porpoising and was being pushed around terribly by the wind and passing vehicles. Not fun. My TT was also lighter than yours to start with. Needless to say, I put my "upgrade" money into a bigger truck. All issues gone. Just my personal experience, you have to do what is rught for you and what you can afford but I would see how much upgrades are gonna cost vs trade difference on a bigger truck. Good luck, none if it is cheap.
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Old 06-07-2023, 05:18 AM   #5
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There is a county road 1 mile North of where I live. The posted speed limit is 45. Other East - West roads North and South of it are all 55 mph speed limits. I never figured out why that specific road has a 45 mph speed limit. It's absolutely no problem running 55 or even faster on it, which I've done hundreds of times, even faster. UNTIL....

One day, I had the fifth wheel in tow and came down that road running at 55 mph and then I realized why the speed limit was posted 45! The dips in the road were positioned in such a way the truck and trailer started porpoising violently. Something I'd NEVER experienced before. I HAD to slow down and got down to 45 and then the porpoising stopped. I could feel the dips, but the truck and trailer did not porpoise any more.

It was then I understood why the speed limit on that road was posted 45. Under "normal" conditions, in a "normal" automobile, one would never feel this porpoising or even detect anything is odd about the road. Add a few hundred pounds to the payload of a vehicle, especially hanging near the rear, and experience the fun!

Ever since that hair-raising experience, I've maintained a 45 mph speed limit on that road, towing my fifth wheel, or driving my small Chevy Colorado pick up.

I can't imagine what that road would be like for a semi-truck driving faster than 45.

So, the BEST solution for your problem is to simply slow down, especially when towing. You did not say how fast you were going and what the speed limit was when you hit that patch of road. A lot of folks complain and fuss about posted speed limits, but the designers of the road had reasons for posting those speed limits for good reasons. Sometimes those reasons are unseen, until you hit that patch of road with just the right vehicle or rig. Then you experience some real issues, where as other vehicles never do. But the "average" safe speed is the one posted for ALL vehicles.

Your best solution, stay under the posted speed limit, especially when towing. Now you know why!
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Old 06-07-2023, 05:31 AM   #6
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I agree with what Max23 posted. The "sticker for the truck" gives information "for the ideal situations" and the "sticker for the trailer" gives the "best manufacturer's guess" on what the trailer actually weighs (without knowing how you load it or where you put the load in the trailer"...

The logical next step in determining YOUR SPECIFIC LOADING would be a visit to a CAT scale, weigh the rig, then without moving from the pads, "unload the WD bars and reweigh" then pull off the scale, unhitch and get a third weight for the truck only.

Then, and only with those weights can you accurately determine how your rig is set up and whether any of those "maximum ratings" are being overloaded or close to being overloaded.
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Old 06-07-2023, 06:08 AM   #7
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John,

Thanks. If you look at the link to my speadsheet above, I already have my actual scaled weights in it and show the margin (green) to the sticker specification. I did this baseline to ensure that I have margin to the specifications. I keep an eye on my tounge weight the most since most of weight that I can't redistribute is near the tounge (propane tanks, batteries, water tanks). I don't haul much water because of this. Overall the TT/TV handle very well even in moderate wind and I don't feel any pull when semis go by. Just the occasional porposing on certain sections of road.
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Old 06-07-2023, 06:58 AM   #8
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Quote:
Originally Posted by Berdan View Post
Danny,

Thanks for the response. The ratings come from the Trailering Information Sticker on the Drivers Side for my specific VIN build configuration. I am not sure where to find better numbers but I think your point is that you are skeptical of the credibility of the published specifications with regard to towing.

Upgrading to LT tires is in my plans and okay on recommending HD shocks and Airlift 1000 (seems more reasonable than 5000s). I already upgraded my TT tires to Carlisle ST E-rated tires.

WDH is a Reese PRO Series 10000/1000 hitch with friction sway control bar. It is set up per the Reese specs.

Brien I am surprised at the actual payload of that truck but who knows anymore. I think your problems are from the basic mechanical makeup of the truck and the particular kinds of roads you encounter. You have scaled and are apparently watching those numbers...which all look good by the spreadsheet. That said;

As Max23 mentioned, upgrading to an HD truck cured his problems and that is the ultimate solution I came to as well. In lieu of that I did all the things I mentioned previously to try to help - none of which eliminated the problem, just made it more manageable.

LT tires are a must IMO then run them at the max on the sidewall to stop as much flex as you can. Same with the shocks. If you don't have a towing package chances are they are lighter duty (mine were on my last 1/2 ton). HD truck shocks will help. The AirLift 1000 system worked well for me. I did not have onboard air and didn't need it. I carried a small 12vdc compressor if I wanted to air up/down. IIRC I ran maybe 5-10psi unloaded and around 30-35psi (?) loaded. They do make a noticeable difference. I considered Sumo Springs (similar to Timbrens) but left the AirLift on. The HD anti sway bar was an attempt to throw anything/everything at it to help with all the shortcomings of a 1/2 ton. Of all the things I did it was the least productive best I could tell.

If it is an option upgrading trucks would be the single best thing you could do (it will still porpoise on certain roads at speed). If you like working on trucks and don't mind spending the money you can make all the upgrades. It will help but won't eliminate the issue. Even with everything I did there were still sections of undulating highway that I drove at a max speed of 50mph so I could at least stay in the "saddle". Good luck and let us know the progress.
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Old 06-11-2023, 07:38 AM   #9
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Quote:
Originally Posted by sourdough View Post
Brien I am surprised at the actual payload of that truck but who knows anymore. I think your problems are from the basic mechanical makeup of the truck and the particular kinds of roads you encounter. You have scaled and are apparently watching those numbers...which all look good by the spreadsheet. That said;

As Max23 mentioned, upgrading to an HD truck cured his problems and that is the ultimate solution I came to as well. In lieu of that I did all the things I mentioned previously to try to help - none of which eliminated the problem, just made it more manageable.

LT tires are a must IMO then run them at the max on the sidewall to stop as much flex as you can. Same with the shocks. If you don't have a towing package chances are they are lighter duty (mine were on my last 1/2 ton). HD truck shocks will help. The AirLift 1000 system worked well for me. I did not have onboard air and didn't need it. I carried a small 12vdc compressor if I wanted to air up/down. IIRC I ran maybe 5-10psi unloaded and around 30-35psi (?) loaded. They do make a noticeable difference. I considered Sumo Springs (similar to Timbrens) but left the AirLift on. The HD anti sway bar was an attempt to throw anything/everything at it to help with all the shortcomings of a 1/2 ton. Of all the things I did it was the least productive best I could tell.

If it is an option upgrading trucks would be the single best thing you could do (it will still porpoise on certain roads at speed). If you like working on trucks and don't mind spending the money you can make all the upgrades. It will help but won't eliminate the issue. Even with everything I did there were still sections of undulating highway that I drove at a max speed of 50mph so I could at least stay in the "saddle". Good luck and let us know the progress.
For what its worth, I accidentally solved my porposing problem. I have a 2019 chevy silverado 1500 crew cab TV. We have a few roads that we travel that caused significant porpoising. We boondock a few times a year and our inverter generator weighs about 100 lbs. I installed a front mounted hitch and carrier so that i could easily load and carry our generator.
Adding 100 lbs to the front totally eliminated any porpoising..
Go Figure

Safe travels and all the best...
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Old 06-11-2023, 07:49 AM   #10
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Yes, a too light front axle can cause any number of problems. What did your scale weights look like before and after? I would think they would show the problem or at least hint at it. That is one reason there's always the suggestion to make sure the WDH is set properly. I'm glad you got it cured.
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Old 06-11-2023, 07:49 AM   #11
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Originally Posted by oldnjrver View Post
For what its worth, I accidentally solved my porposing problem. I have a 2019 chevy silverado 1500 crew cab TV. We have a few roads that we travel that caused significant porpoising. We boondock a few times a year and our inverter generator weighs about 100 lbs. I installed a front mounted hitch and carrier so that i could easily load and carry our generator.
Adding 100 lbs to the front totally eliminated any porpoising..
Go Figure

Safe travels and all the best...
Which is why I recommended weighing the rig "WHILE IT HAS THE PROBLEM" and not relying on an "old weight from when we first bought the trailer".... People change the tongue weight on the trailer nearly every time they load for a trip. Just as you state, simply adding 100 pounds to the tongue weight makes a significant difference. That said, so does removing tongue weight by towing with an extra 100 pounds of food/gear behind the axles on the trailer (think a stocked outdoor kitchen vs an empty outdoor kitchen)....

On nearly any "LD truck" a 100 +/- pound weight change on the tongue is all it takes to dramatically change the towing/porpoising characteristics of any rig that's approaching its "tow rating categories" (one or more, not necessarily all the ratings).....
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Old 06-11-2023, 08:21 AM   #12
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Look at the springs on tow vehicle and tt. You might need an extra leaf in your spring pack on tow vehicle. Also the springs they put on our campers imo are not adequate for the weight. They flatten out within a year. If you have a shop that does suspension near you, take your trailer fully loaded to them. I bet that at the least your spring pack on your tt will need rearching and tempered. Possibly even an extra leaf or two for the weight your carrying. Just my 2 cebts worth.
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Old 06-11-2023, 02:33 PM   #13
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Porpoising suggestion

I encountered severe porpoising in Virginia towing a new 3100RL with a 3/4 ton chevy. It had no problem with the older 5er but the new one had a much heavier tongue weight. I eventually found that if you engage just the trailer brakes via the brake controller, it will calm it down quickly. I tried air bags but they had minimal impact. A few months later I traded the 2500 for a 3500 dually. This was much better, but still has porpoised a few times. I just activate the trailer brakes via the controller and it stops it within a second or two.
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Old 06-12-2023, 04:12 AM   #14
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My new trailer (260rbs) had the similar specs as yours and I towed it with a 2018 Ram 1500. As sourdough said, the 1500 has lightweight running gear. Was I in payload and max tow, yes but the rig would porpoise all the time. I added LT tires, air bags, and moving the weight around and nothing really helped. I went to a Ram 2500 and all the issues went away without changing the WDH or trailer. Sorry unless you have a 1500 built for towing, they are not made to pull these larger trailers.

I did pull my Premier 19FB with my 1500 but that was around 5K loaded, and it would porpoise every once in a while on the PA highways.
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