IDRVr - Right now, there is a lot of internal discussion at GDRV regarding "approved" pin boxes. I'd suggest you call GDRV customer service Monday morning at 574-825-9679 to make sure that the pinbox you're considering is an acceptable application for your '21 Solitude.

Jim

Interesting point. TrailAir is now Curt, a Lippert company. I’ve talked to Lippert and the Curt Flex Air is on Lippert’s approved list. Does it matter what Grand Design thinks as the frame is under Lippert’s warranty, if any? I will call GD to see what they have to say. I’d be surprised if they don’t like a pinbox designed to absorb vertical road shock given the frame issues.

It's probably fine. I think they used to install the same pin box a few years ago. With some recent events on social media related to frames, they are just being careful. It wouldn't hurt to call them. If you do, we'd love to hear about the feedback. If you can't get an answer, let me know and I'll discuss it with some of my contacts.

Jim

Not at all familiar with this product, or anything similar, so might be blowing smoke here. If the pinbox is to be adjusted back to the "ride height mark" after hitching, is the issue whether or not there is clearance between the trailer and the truck sides with the pinbox unadjusted? If you can find the dimension between the king pin and the ride height mark at full compression, would you be able to determine whether you still have clearance for hitching and unhitching? Conversely, can the pinbox be fully inflated (?) prior to hitching or unhitching, to maximize clearance during these operations?

JBill9694 The issue with air ride pin boxes is not specific to the Lippert / Curt one but also the Reese Goose box. The un loaded air bag will extend fully as there is no resistance to prevent the bag from expanding.

There are a few videos that show the goose box usually needs to have the bag pressure relieved to unhook as most trailers will not get high enough to clear the ball when the box reaches the limit stop.

FYI on air ride components. With a fully deflated system that when the bag starts to lift the load, pressure in the bag will remain "constant" (usually within a few PSI) until the upper limit of the bag or a stop is reached. Bag force is relatively constant across it's extension range for a given pressure.

I have the same pinbox on my 22 Reflection 303RLS and love it. Also have bags on my truck. I have about 7" of bed clearance with the B&W puck fifth wheel hitch on highest setting.

I appreciate the feedback. I think it will substantially reduce the vertical shock a standard pinbox imparts to the RV.

I am trying to find out how much higher this pinbox will ride vs. my current pinbox. I have a different truck and a different hitch, so I have no idea if your 7" bed clearance will apply. I may have plenty of bed clearance but I'm already close to 13'6" on overall height, so I need to sort that out as well.

I know all the dimensions but one - how much does the kingpin compress when the pinbox is loaded. I know that dimension "C" in the original picture is 12 1/2" when not loaded. There are two ways I can determine the loaded measurement. The first would be for someone to measuring distance "C" when loaded and with the airbag adjusted for travel. The second would be measuring the distance between the edge of the upper shock housing and the "ride height mark" when the pinbox is resting (not loaded). I've attached a picture showing this as distance "D". Unfortunately, no local dealers stock this pinbox so I can't go look at one.

If there is any way you could get either measurement for me I sure would appreciate it.

I think what you need is the C dimension when loaded. Ideally if COR can get you the dimension from the bottom of the pin box mounting ears to the bottom of the king pin plate (top of 5th wheel plate in the truck) when loaded, this will let you compare to the current pin box on your unit. Also COR needs to provide the holes used or a picture so you can compare to the current mounting point if you need to move the box up or down.

COReflection do you happen to have those dimensions?

I don't need anything regarding the mounting holes or pictures as I have the CAD drawings from Lippert and Morryde for comparison. Unfortunately, those drawings don't show the loaded compression of the Flex Air jaw and the Lippert Customer Service people have no idea - their response to my question regarding loaded compression was "the pinbox is not meant to be used in a completely collapsed condition". DUH!

I only need either of the measurements referenced in my post #8.

Good morning! I can try and get you that measurement this weekend if all works well. I have the camper tucked away in my RV carport for winter and the hitch is not loaded in my truck for the season yet.

Thanks much. If I know the measurement on the shock absorber, a little trigonometry will tell me how much the kingpin plate will compress.