Jackknifing not actually bad?

[timelinex]

I talked to a GD representative today and while we were talking suspension, I figured I would ask just how bad Jackknifing is. He said that is a common myth, but that it is not bad at all for the suspension. He said that compared to the dynamic forces from bumps and regular driving aberrations, the forces (lateral and otherwise) during jackknifing are tiny. That all the creaking, popping and ugly looking angles are all normal operation.

At first I couldn't believe what he was saying. So I re-asked 2 or 3 different ways , making sure he knew what I was talking about. But he insisted he understood and that it's harmless unless there is already issues with the system (he mentioned a few parts that could break if rusted as an example).

What do you guy say to that?

[livinthelife]

I talked to a GD representative today and while we were talking suspension, I figured I would ask just how bad Jackknifing is. He said that is a common myth, but that it is not bad at all for the suspension. He said that compared to the dynamic forces from bumps and regular driving aberrations, the forces (lateral and otherwise) during jackknifing are tiny. That all the creaking, popping and ugly looking angles are all normal operation.

At first I couldn't believe what he was saying. So I re-asked 2 or 3 different ways , making sure he knew what I was talking about. But he insisted he understood and that it's harmless unless there is already issues with the system (he mentioned a few parts that could break if rusted as an example).

What do you guy say to that?

Do you mean "jack-knifing" as in what a semi truck does when it wrecks? Or "Porpoising" like a porpoise does to travel through the water?

Definition from Good Sam site: Porpoising is front to rear bounce; the front hits a bump, then the rear hits the bump, and they both bounce independently of each other, creating an oscillating motion. If the problem is severe enough, it can feel like you’re going to pull the wheels off the ground.

[timelinex]

No, I mean the maneuver where your truck is 90 degrees to the 5th wheel and you are literally pushing the trailer in a circle, in place.

[trailrydr]

No, I mean the maneuver where your truck is 90 degrees to the 5th wheel and you are literally pushing the trailer in a circle, in place.

I don't turn that tight with my 5er, but, on my bumper tow car hauler or boat trailer I have done it many of times, just maybe not as hard as a 90 though... dont like to get that close to the trailer.

When done the trailer tires appear to be leaning in opposite directions and seem to bind on the suspension. It may creek and make some poping noise when doing it especially under a weighted load. I have always considered this normal, and have experienced it with other trailers as well. Also, haven't had any issues from doing it.

[Steven@147]

I talked to a GD representative today and while we were talking suspension, I figured I would ask just how bad Jackknifing is. He said that is a common myth, but that it is not bad at all for the suspension. He said that compared to the dynamic forces from bumps and regular driving aberrations, the forces (lateral and otherwise) during jackknifing are tiny. That all the creaking, popping and ugly looking angles are all normal operation.

At first I couldn't believe what he was saying. So I re-asked 2 or 3 different ways , making sure he knew what I was talking about. But he insisted he understood and that it's harmless unless there is already issues with the system (he mentioned a few parts that could break if rusted as an example).

What do you guy say to that?

It's not a myth. Turning an RV 90* like backing into a site, puts a huge amount of stress on the tires, rims, leaf springs, U bolts, shackles, frame hangers, frame, bushings and the equalizer between the axles. Lots of people have broken the leaf spring hangers doing this a lot with the common "U" hangers without the V clips installed. On gravel or grass it isn't near as bad because the tires will slip more, but on concrete or asphalt the tires bite and its terrible for the suspension.
RV's are not like semi trailers that have real beefy suspensions and tandem trucks. RV suspensions like from Lippert are built cheaply. I don't ever do this if I can keep from it. I will cut in and pull forward many times trying to keep a minimum angle when backing into a site especially on asphalt or concrete.

[jleonard]

It's not a myth. Turning an RV 90* like backing into a site, puts a huge amount of stress on the tires, rims, leaf springs, U bolts, shackles, frame hangers, frame, bushings and the equalizer between the axles. Lots of people have broken the leaf spring hangers doing this a lot with the common "U" hangers without the V clips installed. On gravel or grass it isn't near as bad because the tires will slip more, but on concrete or asphalt the tires bite and its terrible for the suspension.
RV's are not like semi trailers that have real beefy suspensions and tandem trucks. RV suspensions like from Lippert are built cheaply. I don't ever do this if I can keep from it. I will cut in and pull forward many times trying to keep a minimum angle when backing into a site especially on asphalt or concrete.

Yes once you get past 45 degrees, things get stressful in a hurry.

[trailrydr]

Here is a video of a simple turn done by a tandem axle trailer on dirt.

https://m.youtube.com/watch?v=qIFdltJRqoQ

And another sites discussion on the same topic:

https://heartlandowners.org/threads/...n-axles.24334/

[traveldawg]

I'd agree with the others that there is a LOT of stress when backing. And the steeper the angle, the more stress. I'd point out the failure of my frame to support that conclusion. My frame's webbing cracked above the rearmost spring hanger which required frame stiffening repairs. I had expected the spring hanger to break first but that wasn't my case.

Here is the post about that...

[Easycamper]

Definitely less force than going down the road, but force in a different direction. For sure tight turns help loosen lug nuts if nothing else.

[timelinex]

Hey guys, don't shoot the messenger! I was very skeptical too, but he insisted it's overblown. No idea, but would be great to hear from other tech's.

I know there are alot of anecdotal accounts of "hey look at what happened to my frame/bearings/hangers"... But how many of them could be verified to for sure be done by the sharp turning? Maybe it was done on the road from bumps/rocks/etc and it was noticed after taking a close look after sharp turns? I don't think he ever denied that it puts stress on parts... Just that the parts get orders of magnitude more stress at speed or with dynamic actions.

If you guys ever call GD for something else, maybe throw in this question at the end. This rep said he has been working with trailers, including during fabrication part, for over 15 years. But lets see if a different rep has a different take!