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Curt Flex Air 5th Wheel Pin Box Review

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Review of the Curt Flex Air 5th Wheel Pin Box


Hey everybody, how's it going Today, we're gonna be going over the Curt Flex Air Fifth Wheel Pin Box, designed for the Lippert 1621 bolt pattern. The Curt Flex Air is what's known as a cushion pin box. Now, with the cushion pin box, we're gonna have two types of cushioning and stabilization. Actually three, if you count the pivoting mechanism. So, the skid plate here is actually gonna pivot back and forth when we go over those bumps in the road. And what this does is this actually compresses the rubber between these two plates here.

So, our first step of shock absorption is gonna be this rubber here and our pivoting head. Now, that's not gonna get rid of everything, but what we don't get rid of is gonna be transferred up to the airbag here. So, our airbag is gonna be a great job of getting of everything that's not absorbed by that rubber spacer there. So, once the airbag expands and contracts, we're gonna have our built-in strut here which is gonna help control that airbag, so we don't have any violent movement. So, overall, all these mechanisms are gonna do an excellent job of help cutting down on those road vibrations, making for a much smoother ride with your trailer.

So, a standard pin box on your trailer isn't gonna have any of this. It's not gonna have a pivoting head. It's not gonna have it built-in strut, and it's not gonna have an airbag. Now, you're probably thinking, why do we need all this So, I wouldn't say it's a requirement but your standard pin boxes, they're basically gonna be transferring all the road shocks when we hit a pothole, we're going over some bumps in the road, everything is gonna be you transfer directly to the vehicle and you're gonna be feeling all those bumps in the road. It's actually gonna rely on the vehicle suspension and partly the trailer suspension.

But when you add a cushioning mechanism between the truck and the trailer here, this thing is gonna absorb all that road shock there. So, we're not gonna be transferring it to our vehicle. So overall, it's gonna be making our ride that much more pleasurable. And it's also gonna help maintain our fifth wheel trailer here, because it's not gonna be rattling around as much. A lot of those road shocks and vibrations are gonna be absorbed into one of these three mechanisms here to make for an overall, a smoother ride.

And it's gonna cut down on that chucking and jarring feeling. You're not gonna have any of those issues that you would normally by upgrading your pin box. So, on the top of the pin box we're gonna have our Schrader valve here. So, we have this little yellow cap on here, and this is basically just like a standard air chuck fitting like you would find on your tires. So, what you're actually gonna do is you're gonna couple up to your trailer and that's gonna in turn compress the shock here in the front. And then once you do that you can begin inflating the valve here into the predetermined point on the front of the shock. So, there's actually a line on your shock absorber here. So, this is gonna let you know how much pressure we need to put into our airbag. So, it's not an exact psi, basically, when you couple the trailer, this is gonna be compressed and that line is gonna be hidden behind this outer sleeve here. And then when you begin to inflate the airbag, it's gonna show more of this inner tube here and you're gonna stop where this line here meets with this outer sleeve. So, that's gonna let you know, you have the correct pressure. You wanna be careful not to overinflate the airbag 'cause that's gonna make your ride much more stiff and rigid. But if you underinflate it you're not gonna be utilizing the full shock absorption here of our system. Now, what this comes down to is, we're gonna be improving the ride in our vehicle and we're gonna be increasing the maintenance life of both our trailer and our vehicle. So, without all those extra vibrations, we're gonna be keeping the trailer suspension intact and working order for much longer would normally. It's not only gonna cut down on the wear and tear of our trailer, it's also gonna cut down on the maintenance that we're required for our tow vehicle, because the trailer isn't gonna be bouncing around as much, therefore the suspension on our vehicle isn't gonna incur that much wear. So, in regards to capacity, we have two different options. We have an 18K version and a 21K version. Now, in order to pick the right one for your particular trailer, you just simply need to look at your GVWR. And make sure the GVWR of the trailer is no more than the capacity of the pin box. Now, you guys may be thinking, oh, I just wanna get the 21K because it's the highest rated option, therefore it's gonna be best. Well, that's not necessarily true. The closer you are to the capacity without exceeding it, the more shock absorption you're gonna have with your pin box. So, it is important that we cover the capacity of the trailer, but we don't wanna go too far over, because we're gonna be lessening the shock absorption here of our pin box. So, another common question we get here at each trailer when someone's wanting to replace their pin box, is they're worried about the dimensions. Whether they wanna gain height or they wanna decrease height or they're looking to increase their turning radius. Now, unfortunately, you really can't gain or lose anything from a new pin box, because all these are gonna be mirrored towards the same shape of the one they're gonna be replacing, which is that Lippert 1621. Therefore the distance from the bolt holes to the center of the kingpin here or the distance from the bolt holes to the bottom of the skid plate is gonna be the same, pretty much for all Lippert 1621 pin boxes. So, all of our pin box components are gonna be made of a very thick and sturdy steel. And they also have a nice durable black powder coated finished, which is really gonna protect our fifth wheel or our pin box here from rusting corrosion. A lot of the times, you're banging these on the fifth wheel hitch trying to back them up. So, they are kind of an abused item. Really, there's gonna be a lot of subjected wear to these things. So, you need to make sure that they're gonna be stout. And it's really important that powder coating holds up, because if you nick and scratch this and expose the bare metal underneath they will rust. Having that nice durable will finish there is really gonna help protect that metal from time to come. And I would also like to point out here that this fifth wheel hitch is made in the USA. So, you know you're getting a quality product. So, one thing you do need to be aware about with this particular pin box here and all cushion pin boxes, is that you can't use any sort of fifth wheel gooseneck adapter, such as the ones that bolt to the bottom of the skid plate here. So, just keep that in mind, you won't be able to use any of those adapters. So, in regards to installation, this isn't really bad at all because let's face it, it's actually only four bolts per side. So, there's no cutting, drilling or welding whatsoever required, but these things are heavy. I mean, they can weigh a couple hundred pounds. So, it is gonna be hard to get the fifth wheel hitch into position and remove the old one. But if you got a couple buddies around, usually about four people are gonna be able to manage getting this installed in place. Obviously, the most ideal thing would be to have a forklift of some kind or some sort of lifting device. You guys can get creative here, but aside for in that, nothing is particularly challenging, they're just heavy. So, now that we've gone over the pin box a little bit more in detail. Let's go ahead and couple it to our trailer. And take it out on the test course we have here at etrailer, so we can show you how well it performs. So, as you can see here we go over those bumps, the head on our pin box there, is going to pivot just slightly which is gonna compress that rubber in between the skid plate there. That's gonna get rid of a lot of our shock, but then the rest of the shock is gonna be transferred up to that airbag there. And you can see our shock there helping our airbag return normally to the right position. And overall, this is just gonna do a great job of helping smooth our ride. That's gonna do it today for our look of the Curt Flex Air Fifth Wheel Pin Box..


Info for these parts were:

Employee Dustin K
Video Edited:
Dustin K
Employee Jonathan Y
Video by:
Jonathan Y
Employee Conner L
Test Fit:
Conner L
Employee Michael B
Installed by:
Michael B

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