pin height on the coach with HDT

[lockmup68]

Great meeting everyone. Took off Tuesday eve, Aimee and Carsyn headed back to Nashville and I headed to Casper, WY to pick up the trailer. Still waiting on a couple of parts to arrive tomorrow to be finished, but I'm in the Fort Casper RV park for the night. Holy smokes the rig and trailer are long! Only 1566 miles home to get used to it.

 

When they pulled the trailer out of the shop with the shop truck (ford F350 dually) the trailer was riding level. When I hooked up the Intl to it, the front legs only had about 6 inches of clearance to the ground and the nose of the trailer was significantly lower than level. I pumped up the air bags in the trailer saver to 80 just to get it out of the parking lot onto the level street without dragging the landing gear. I have the 3rd air bag.

 

I should have taken pictures, but the nose was significantly down on the trailer when hooked to the International. So we dropped the pin box to the lowest level (one more notch), gaining two inches and that helped, but the nose is still low. When I put the weight on the truck, the air leveler valve on the rear suspension kicks in and raises the rear back up a bit after the weight is on (as it should). But nose is still low.

 

at 80 lbs, the white line that the manual says to inflate to is 2 inches above the level of the plate, so it is way over inflated, yet the nose of the trailer is still too low.

 

So, either the hitch is mounted way too low, or the pin box is short? Since it was level on a stock F350 dually (96), I'm thinking the hitch is low?

 

Also, when hooking up and unhooking, the kingpin hits the rear crossmember of the bed. I had to back in, lower the king pin in front of the rear cross member, to the head height, then back onto the king pin. Reverse when unhooking, open jaws, pull forward about 9-11 inches until the kingpin just clears the head, then raise the jacks and lift the king pin over the rear crossmember.

 

Am I out in left field? Could the hitch have been 3 inches low the last 5 years since the conversion?

 

Weather is nice in Casper at least!

 

Shannon

 

[Shallow Draft]

Seems to me that 46-48 inches is about the correct hitch height on the truck. You should be able to back in without interference from a cross member.

Lowering the pin height will not solve the cross member issue.

[Star Dreamer]

Sounds like you need to raise your hitch but we really need dimensions and pictures to know for sure.

 

Unhook the trailer and put it level. Measure from level ground up to pin.

 

Put hitch at correct location for tide and measure from top of hitch plate to ground.

 

The two dimensions should match or be close. As posted previously there is a common dimension but it really does vary based on trailer and truck.

 

Dave

[Imurphy907]

My truck has an ET jr low pro hitch. When we picked up our trailer the front was to low by about 4-5" Since we were 4800 miles from home I stopped by a steel shop and had chunks of 4x6 tube cut for me. in the parking lot of the lowes in ft worth I drilled all the holes in the steel and raised my hitch the 4". Its not quite level but dang close. I will be putting on a comfort ride hitch, that hitch is quite a bit taller then mine so it should level out. the pinbox on my trailer was not adjustable. And the dealer had no interest in trying to help. Guess that's why I get for buying a trailer at the motorhome yard.

[Hot Rod]

46-48" seems to be pretty standard. I have a trailer saver on my TopKick that we intentionally installed at 43" due to the low hitch height on an older race car trailer we were towing at the time. When we bought a fifth wheel toy hauler instead, we found the pin to be at 48". We had one hole to drop it, on the trailer, getting us to 46". Been able to get by as noted by pumping up the air in the hitch to around 90# to get it level (we only have the two bags), but that is not good. We really need to put some spacers in between the steel plate on the truck and the hitch. In our case some 4x4 heavy wall tubing will do the trick. The biggest problem in the meantime is that those air bags should ideally be around 50# for best cushion and travel. I've been told by folks that know that an air bag at 100# is basically a solid rubber block, so your trailer is getting the full beating of the mdt/hdt truck and no benefit of the air hitch.

[HERO Maker]

This 46 to 48" hitch height IS NOT the standard anymore! For example, DRV is now building them at 50" hitch height to accommodate the pick up market with their higher bed sides!

As I have mentioned before, and as was mentioned in this thread, depending on your trailer and how it was put together (air suspension, inverted axles ....) you need to measure the pin box with your trailer level, and then set your hitch on your truck to that. The big major problem with this is that you may not be able to pull another persons trailer, or you may have to raise or lower your hitch if you get another trailer.

It sure would be nice to have a "standard", but I think we are getting further away from that every year.

Let me clarify Dave's statement. Measure from level ground up to the TOP of the pin. That way your two plates will be at the same height.

[MrSeas]

Sometimes being level fore to aft both visually and using your tape measure doesnt always mean your axels are loaded "equally" Just throwing that out there.

So many variables to the situation.... each rig will be set according to the " owners" wishes.

[HERO Maker]

This solid rubber block business is just not true! Yes, if all the pin weight requires is 60 lbs, then putting 100 in it will make it not ride very softly. But like all of our trailers are becoming more and more built, and loaded, to our needs, if you have a 7500 lb pin weight, you will need to put a lot more air in those bags to make that ride more softly. The extra weight will still exercise the rubber component of the bag, as it was designed for.

[MrSeas]

?

[HERO Maker]

?

Think about it this way. Some of the hitches out there have leveling valves to keep it at the correct height. If the load on the hitch is real heavy, it will take more air to bring it up to the ride height.

Same as the air bags on the truck.

[Hot Rod]

I can't find it on the Hensley website anymore as the revamped the entire site, but my info on the "solid rubber block" came from Hensley themselves in regards to whether you need to upgrade to the 3 bag system from a 2 bag system. Their statement was 100# was too high, essentially a solid rubber block, and if you had to run 100# on the two bag hitch to get proper ride height at the line, that was the point to go to the 3 bag system to lower the pressure and restore an air cushion effect to the hitch.

[hone eagle]

Henry has said as much too, much over 50% pressure the "squish" is gone and you have a solid block.

[HERO Maker]

This from Trailer Saver's Owners Manual online:

 

"The TSLB is not to be inflated to a specified air pressure but to a specific level. Do not inflate to greater than 100 PSI! Follow these steps for proper inflation:"

 

My visit to Dave at TrailerSaver in Kentucky (the original designer and manufacturer of the TS before Hensley purchased them) was an eye opener. I explained a problem I had the first few months after owning the TS in that the 3rd bag had somehow rubbed on the edge of the steel platform and sliced a small hole into the bottom of the bag. One corner of the edge of the platform was pretty sharp. When the air leak happened, they sent be a new bag and platform quickly and I installed them without problem.

 

That is when Dave asked what my pin weight was. 7,000 lbs I replied. Dave said that I must put between 95 to 100 lbs pressure into the bags (springs) and it would then be within the working range of the system. I did explain that it was being pretty much preached on our forum that anything above the 35 to 65 lb range would make it a hockey puck and not cushion the ride. He said not so with that 7 to 7.5K pin weight. He also said they test it a lot higher than that but it didn't give them any more benefit, so 100 lbs max would be recommended.

 

And the discovery was that when my bag was sliced by a sharp corner of the platform, I had too little air in the system (for my weight) allowing the bag to "sag" and rub on the platform.

 

There have been a few TS owners here who have installed leveling valves on their units, and like our trucks, as long as we raise the hitches to the suggested height, an air gauge is not even needed. The system will put enough air into the springs for whatever weight you put onto the pin. I am considering installing the leveling valve onto mine. As we know, anything with air will end up leaking.

[MrSeas]

Did you weight your new rig at the HDT Rally this year?

If so what are your weights? Pin height?

Do you still use the TS hitch? What air pressure are you running to bring the "white line" to its proper position?

[HERO Maker]

Yes, I did have Trey and Susan weigh my rig this year. I also had them weigh the Teton a couple of years ago after I had the bed built. At that time we were able to take 900 lbs off of the pin by putting some of my stuff in the drom and storage areas of the new bed. At 6,100 lbs, it required about 85 to 90 lbs air pressure.

 

The weights are:

Trailer 23,675 lbs

Pin 4,200 lbs

Top of Pin Height was at 50 inches. Wasn't a problem because the Teton Air Suspension required 49 3/4 inches.

Now running my air at around 70 lbs. May lower it a little more.

Slow air leakage somewhere, so I may install a leveling valve, that I can bleed off when hitching and unhitching.

[MrSeas]

Rocky,

 

Thanks for the weight info.

What were the individual axle weights?

With a pin weight of 4,200, you have a hair less than 18% of your trailer weight on the pin.

Are you level fore to aft visually and by the tape measure?

Have you noticed any "pin float" with the lower percentage of pin weight of the DRV vrs the Teton?

[GlennWest]

I was aware DRV was doing this, lighter pin weight. Not very smart my opion.

[Bill LeMosy]

According to Henry Szmyt the industry standard for hitch height is 47”. Our Summit, with the MorRhyde pin box at its lowest possible height, needed a 50” hitch height to be level. Henry’s solution was to lower the pin box 3” by welding on additional sides to the pin box; he didn’t want to alter the hitch itself since it was at standard height. Here are pictures of what Henry did:

 

http://www.rvnetwork.com/index.php?showtopic=122297&hl=

 

We had had a 2,000 lb. difference between the first and third axles (with the front axle right at its maximum rating). After the modification the difference is 200 lb. with the pin weight at 21%.

[holaCG]

So.... It seems like more new trailers are coming with the pin height closer to 50" (mine measures that). I am just starting to get plans together for an HDT and was always planning on getting the pin box lowered (wish I could get lucky like TXdiesel and get grand design to send me one!) but would it be ok to just set the ET hitch up for 50" pin height? Is there any downsides to doing that?

[Star Dreamer]

You will have a hard time pulling another trailer that might have the lower pin height. We may have to see if we can get someone like BMZero to design us a lift mechanism to raise and lower the hitch at a touch of a button.

 

Right now with our bed design, I should be able to flip the mounting angles which holds the plate for the hitch and be able to raise it 3" that way. Any additional would need some spacer blocks or a lower pin box.

 

Dave

[HERO Maker]

Rocky,

 

Thanks for the weight info.

What were the individual axle weights?

With a pin weight of 4,200, you have a hair less than 18% of your trailer weight on the pin.

Are you level fore to aft visually and by the tape measure?

Have you noticed any "pin float" with the lower percentage of pin weight of the DRV vrs the Teton?

Axle weights:

Front 6200

Mid 6950

Rear 6325

 

Pretty level visually.

 

I'm soon going to add more weight, by installing Bludot air/hydraulic braking system, and transfer weight from mid coach to front and also onto truck.

 

Teton was very heavy and after I installed the hitch up camera I could watch the action of the air bags doing their thing. New trailer does seem to move a lot more just cruising down the road. I wish my seller would have had the axles moved more towards the rear like the original owner of the Teton had when it was built. Yes, I would like more pin weight.

[lockmup68]

Just got home from picking up the Teton in Casper, WY after leaving Hutchinson. 2,982 miles for the first trip in the HDT. First half bobtail.

 

Here are some pics of the hitch height. The pin is a telescoping pin and I lowered it to the longest setting, which I think gives about 2 inches longer. Before lowering, the front of the trailer was just 4 inches off the ground. I moved to longest hole set and pumped the hitch bags up to 90 for the trip home. The trailer is empty, so I assume it will just get worse when full.

 

With the trailer on and the hitch at the white line level, the hitch head/pin level is at 42 inches above the ground. The trailer level is 47 inches.

 

Reading all the posts in the link above, I believe I need to lengthen the telescoping pin box or raise the hitch 4 inches. Since the bed was made to drive vehicles up on it and over the hitch, I'm leaning toward lengthening the pin box and adding more adjustable holes. What are your thoughts?

 

I also need to notch the rear cross member so I can hitch and unhitch without the kingpin hitting the back crossmember of the bumper. It's been hit a few time by the previous owner and has a nice bow to it.

 

Pics:

https://drive.google.com/open?id=0Byid2fVbXev6VDFsQ244eGxaUkU

[HERO Maker]

What type suspension do you have on that Teton? It looks like it is riding level, but I'm thinking you have air suspension?

[lockmup68]

What type suspension do you have on that Teton? It looks like it is riding level, but I'm thinking you have air suspension?

it's not level and the air bags on the TrailerSaver are at 90 lbs right now. The pic was in a walmart parking lot and doesn't show the nose down as well.

 

The suspension on the Teton is the mor ryde IRE, which is not the independent suspention, but looks like floating equalizer boxes? they can be adjusted for 2 or 4 inch lift. The entire trailer is so low, I'm thinking of raising it up 2 inches to start. That would put the pin box even further out of wack.

 

Is it just me, 7 inches under the front legs is not enough clearance for pretty much any gravel parking lot with a few pot holes, much less any boondocking location? Or am I overthinking this?

[Jack Mayer]

The standard hitch height is 47". There are some that run 48". That is for the truck/semi trailer induustry.

 

There is NO STANDARD that I know of for the RV industry. Most trailers "used to be" in the 47" range. Now, MANY trailers are in the 49-51" range on the "bolster" plate (not that RVs have much of a bolster plate ).

 

You have to decide if you want to modify the truck for your trailer situation. If the truck is not at 47" then I'd first consider the consequences of getting it there. If that will not give you what you need then I'd modify the trailer as required/possible. Only then would I consider mounting the hitch on the truck higher.

 

At some point, if you are far off level andn cannot adapt the equipment with adjustments they you are going to have to change the truck hitch mounting or the trailer. But first raise your trailer if you feel like you need to. An exceptionally low front on a trailer being pulled by the typical HDT will risk front damage in deep dips. That is because most HDTs mount the hitch well behind the axle and in a dip the long back of the truck pushes the hitch even farther down thanks to the overhang/cantilever. So consider all aspects before modifying anything.

 

As to the air bags and their "hardness"....you have to know the rating of the bag. All air bags have a sweet spot, which is the intended operating setting. Putting too much air in the will put them outside of that sweet spot and cause a very harsh ride. While it is not the same as a "rubber block" it simply is not giving you the cushioning you are expecting. It really can be quite harsh, depending on the bag rating and where your air pressure is relative to that. It is a linear relationship. Too little air in the bag (again, outside the sweet spot) will cause wallowing and lack of cushioning. You may bottom out...or you may TOP out on a hitch. Especially if you have too little pin weight for the intended operating range and the bag starts rebounding....remember, the more it goes down, the more it will go up. An HDT may exasperate this, because of the hitch position inducing a lot more "whipping" motion up/down into the ride in a dip.