Porpoising

[GMCPapa]

Hi all. We are looking to purchase a Jayco TT, but before purchasing we decided to rent one the approximate size and weight that we would like to buy. I picked up the rental Jay Flight SLX267BHSW last night for a 1000 mile round trip to Pigeon Forge Tennesse from northern Illinois. It's 5700 lbs. and i'm towing it with a 2016 GMC Sierra 1500 which is rated for 9100 lb. towing. They put a weight distribution hitch on (solid bars type) and told me it is to minimize or eliminate porpoising. Driving it home, it was bouncing (assuming that's the porpoising) quite a bit.
Is there any way to reduce this, and if not, will a 1000 mile trip with porpoising hurt my truck at all?
Thanks!!

[bansai]

You double posted this, I replied here - http://www.jaycoowners.com/forums/f1...tml#post513469

[dalebra]

Sounds like something changed from going to Pigeon Forge and going home.
How about the distribution of cargo in the TT? Or did you go a different route to and from and the roads were different?

I'm sure others will have some other ideas too.

[sennister]

The WDH is really there to level out the truck and shift the weight to the front axle so you can safely maintain steering. You are carrying a lot of weight and it is going to handle different. Will it hurt the truck? Not really, will it shorten the life of something like the shocks, probably.

Things that will hurt the truck are exceeding the max hitch weight, max axle weight and cargo limits. That 9100lbs of trailering capacity mean nothing as you will blow past those other areas I mentioned well before getting close to a 9100lbs trailer when you factor the 13-15% hitch weight being carried by the truck.

My Yukon has a trailer rating of 8100lbs but I start blowing past the hitch, cargo limits with a trailer that weighs 7000lbs depending on how it is loaded.

[TWP723]

You need these!

[wags999]

I have found the porpoising was caused more by the road conditions. When they pour the concrete roads they do it in sections. Each section is separate from the next, if your at the right speed your truck is going up as the trailer is going down. Illinois was one of the worst states for this. If you slow down you will see this dissipate greatly. Also the length of the tt makes a difference. Some sections of I 90 in Wisconsin also were horrible.


Good Luck...

[Jagiven]

Hello, what a good plan! As for porpoising, a WDH does not remove that affect, it does the opposite, it adds the affect. A properly sized and configured WDH will minimize the amount of porpoising. Some roads are horrendous at creating porpoising, if it is a multiple lane highway, I'll move over a lane to locate smother pavement.

As others have said, a WHD is designed to restore proper vehicle ride conditions so you can safely steer the TV.

I suspect the rental facility, just put on the hitch with very little care. They may not even grabbed the right rating load bars. What I have found, is over sized bars create more tension, and more porpoising.

[Dustdevil]

The WDH, or the way it's set up, can magnify that effect you're calling "porpoising". But it's not really causing the problem. It's mostly the condition of the road. In most states, vehicles while towing must remain in one or two right lanes of the highway. Those are also used by large semi tractor trailer rigs, which pound the pavement into a wavy surface, even if it's concrete poured in sections. Especially if it's in sections. The sections get warped and sagging at one end or the other, and make a washboard surface that bounces you around. If the distance between axles on your particular combination of vehicle and trailer is just right, it will magnify the effects at certain speeds. No way around it except a different combination of axle points (longer trailer or longer tow vehicle) or different speeds. Slower is usually better, because you typically don't want to speed up when you are seeing problems already. Other than that, it's a bit of the luck of the draw. There will be certain roads which have a rhythm that is just wrong for your particular setup. Endure and escape as soon as you can to another route, if it's convenient.

[eng45ine]

Originally Posted by wags999

Illinois was one of the worst states for this.

Truer words have never been spoken! I-88 is terrible between I-355 and Orchard Road. UGH!

[314BHDS]

Porpoising happens more often with a longer trailer,i found the best option was install air bags and problem was solved.

[Dustdevil]

The biggest problem I found is when the wheelbase of the tow vehicle is such that the front wheels are in a low spot the same time that the rear wheels are in a high spot, and vice versa. My old tow vehicle was a 2003 Duramax Crew Cab Short bed pickup, and some roads saw no problem while others it was like a hobby horse. Blacktop highways were usually the best, while sectional concrete highways were the worst. It's sort of random as to how bad it is. Some highways much worse than others. A heavy trailer with high tongue weight makes it worse, even with a WDH, because of the high inertia. The trailer or FW just tosses the tow vehicle around.