Hitch Placement

[Overthinker]

I’m not smart enough to figure out how to search the HDT section instead of the entire site for my question, so I’m just going to ask.

It seems 99% of the HDT’s have the hitch behind the axles which makes no sense to an old farm boy.  I was alway taught to install my hitches just in front of the rear axle.  With practically everyone placing their hitch well behind the axle, I would really like to have a better understanding of the rational as well as the pros and cons.

I’m really concerned about overall length and weight distribution.  Some of the singled trucks appear to be squatting even while driving so I doubt their bags are dumped.  We have a 40’ 5th wheel with about 4K-5K on the pin and will have tandems on our truck.  I was thinking the best solution might be to place the hitch 1” in front of the rear most axle to split the difference between most setups and true axle center but I also want to know how it effects maneuverability.  Our crew cab long box dually is difficult to maneuver in tight campgrounds especially when there are campers or trees are on the other side of the road from our site.  The HDT has about 4-5d more wheel cut than my current truck which will help but we are ordering a 217” WB which is about 27” longer WB than our truck.  We aren’t going to be hauling anything so we can place the hitch as close to the cab as clearances will allow, which in my mind will help with aero as well as shorten our overall footprint.

I would really appreciate hearing from someone that has pulled/backed a 5th wheel with the hitch in both locations to get an accurate comparison.  

Thanks so much for your input.

 

[GlennWest]

Camper tracks better with Hitch at rear. Cuts instantly like a pull behind. Also balances out truck better. Our 4-7k pins is light for your truck. Most front, steer, axles are near max. So off loading them some is a plus. Yes it becomes a little longer. A straight down pin box will shorten that. Depending on yours could help a lot. Also adds room on deck. I think you will have clearance issues in front of rear axle. Hitch will mount down in chassis. Be too high on top.

Edited January 18, 2021 by GlennWest

[jeffw]

I think part of the driver for the hitch location is the design of the trailer. Commercial trailers are generally 'open' underneath the 5th wheel pin, which allows the tractor to get 90deg to the trailer (to jackknife it).

Most recreational trailers aren't like this, so you wouldn't have the ability to turn tightly without the truck contacting the trailer.

[jeffw]

We tow a stacker racing trailer, and when i'm at the tightest getting thru my driveway, it's not possible to walk between the truck and trailer. That would be at 90deg or so. This picture shows the truck/trailer about 45deg:

[Randyretired]

Our hitch is 5' beyond the original frame.  It lightens the front axle some and adds weight to the rear axles.  We have a short wheel base and combined with the hitch that far back we can get into some tight spots.  I built this setup many years ago and it is safe and maneuverable but long.  One problem with placing the hitch over the axles is fitting the hitch between the frame.  Air hitches need to be mounted down between the frame to obtain proper hitch height.  There is a lot of stuff over the axles between the frame rails.  

[steiny93]

To get 3 quads to fit I had to push the hitch about 34" behind the rear axle.  (I could change the hitch between short and long via changing out the brackets; so towed a lot between the two).

Toyhauler was just north of 4k of pin weight with the garage empty.

The HDT wasn't out of spec on the weights (front / rear) axle in either config.  The trailer did track significantly better with the hitch pushed to the rear position and backing was much more responsive.

 

[Overthinker]

Thanks for the responses everyone.  That’s interesting about the trailer tracking better.

I forgot to mention we hooked our trailer up to the commercial hitch on the test drive truck and we had plenty of clearance with the hitch moved backwards or centered.  We didn’t attempt to slide it forward.  Prior to hooking it up I went through a series of maneuvers in my 1 ton with the trailer and then attempted to replicate them in the HDT.  I attempted every maneuver I could think of on the lot and didn’t have any problems.  I honestly couldn’t tell a huge difference and I think this particular HDT had a 239”WB.  

The most notable difference was the ability to see the front of the HDT and the sides with the hood mirrors.  Those things are amazing because i can see all the way down the side of the trailer and I can easily tell where my front corner is for clearing things.  The 2020 GMC HD’s hood is so big you have no idea where anything is at.  You have to open the front camera app which is a pain.  

[rickeieio]

You've not mentioned hitches.  What you've written so far leads me to believe you may be considering using the commercial hitch.  DON"T DO IT.  Air ride is best, but there are a couple alternatives that might be "good enough".

So, the diving force putting the hitch so far back is that an air hitch simply won't fit over the axles.  The better handling is a benefit.  And yes, I'm an old farm boy with lots of trailers and a few other semi's around.

[Big5er]

One other consideration is that our rv's weigh less than a commercial trailer. A bobtail truck rides rougher than a truck towing a loaded trailer.  Our light weight trailers do not even begin to get into the trucks suspension, hence the advantage of a air ride hitch. Moving the hitch back puts more weight into the suspension,  improves the ride and let's the air suspension on the truck do its job. 

My HDT,  bobrail, rides better after the bed was built and installed. It rides very nice with the smart and trailer.

[Overthinker]

See below

Edited January 18, 2021 by Overthinker
Just figured out how to reply:)

[Overthinker]

1 hour ago, rickeieio said:

You've not mentioned hitches.  What you've written so far leads me to believe you may be considering using the commercial hitch.  DON"T DO IT.  Air ride is best, but there are a couple alternatives that might be "good enough".

So, the diving force putting the hitch so far back is that an air hitch simply won't fit over the axles.  The better handling is a benefit.  And yes, I'm an old farm boy with lots of trailers and a few other semi's around.

 

1 hour ago, Big5er said:

One other consideration is that our rv's weigh less than a commercial trailer. A bobtail truck rides rougher than a truck towing a loaded trailer.  Our light weight trailers do not even begin to get into the trucks suspension, hence the advantage of a air ride hitch. Moving the hitch back puts more weight into the suspension,  improves the ride and let's the air suspension on the truck do its job. 

My HDT,  bobrail, rides better after the bed was built and installed. It rides very nice with the smart and trailer.

No way would I consider a commercial hitch.  We currently have a TrailerSaver BD5 and will continue to use an air ride hitch possibly switching to ET in the future but TrailerSaver is giving us a deal trading our BD5 in because we hardly used it.  

We also plan to add a heavy bed (approx. 4K lb plus gear) to increase weight on rear axles.

[Alie&Jim's Carrilite]

In the pickup truck world, you had to have the pin over or slightly forward of the rear axle to evenly load the pickup suspension.  Even with todays Superduty 450 and better, the hitch still has to be over the axle.  

In the HDT world, our 4-8k pin weights are nothing compared to the commercial trailers so it doesn't really matter where the pin weight rides.  In the early years, many folks did single the rear and placed the hitch as close forward over the axle as they could thinking they had to like the pick up truck world.  It has been proven not necessary over the years.

[dennisvr]

If I read it correctly you will be ordering a new truck to your specs.  I'm curious as to why you would spec it tandem.  Most, especially if their not carry anything on the back goes single rear axle.   Just wondering.

[Lance A Lott]

I was wondering that as well. I would do a locking differential for sure, my personal opion only but 16k pounds spread over 8 tires is only 2k per tire over 4 is ofcourse 4k and to me that's not much of a contact patch unless you run the tire at a very low psi. 

[Brad NSW]

We kept ours double, based on axle weights.  With the Smart Car, Big Drom box and 8K pin weight, we couldn't go single w/o over-weighting a single axle.  With the hitch behind the axles, we see two advantages: 1) tracks better around corners, 2) responds much quicker when backing, so we get into spaces some p/u's have trouble getting into, even though we're 66ft long!  The big disadvantage of being way back, is that it amplifies the up/down/left/right forces.  We think we found a sweet spot about 4ft back.  Good luck on deciding your hitch placement.  Go to one of the rallies if you want some hands on and visual feedback. 

[Overthinker]

7 hours ago, Brad NSW said:

We kept ours double, based on axle weights.  With the Smart Car, Big Drom box and 8K pin weight, we couldn't go single w/o over-weighting a single axle.  With the hitch behind the axles, we see two advantages: 1) tracks better around corners, 2) responds much quicker when backing, so we get into spaces some p/u's have trouble getting into, even though we're 66ft long!  The big disadvantage of being way back, is that it amplifies the up/down/left/right forces.  We think we found a sweet spot about 4ft back.  Good luck on deciding your hitch placement.  Go to one of the rallies if you want some hands on and visual feedback. 

Thanks that’s what we are looking for.  We don’t live far from Crossville and might head over in April.

 

[Overthinker]

11 hours ago, dennisvr said:

If I read it correctly you will be ordering a new truck to your specs.  I'm curious as to why you would spec it tandem.  Most, especially if their not carry anything on the back goes single rear axle.   Just wondering.

 

10 hours ago, Lance A Lott said:

I was wondering that as well. I would do a locking differential for sure, my personal opion only but 16k pounds spread over 8 tires is only 2k per tire over 4 is ofcourse 4k and to me that's not much of a contact patch unless you run the tire at a very low psi. 

We will not be hauling a car but will camp in the truck and haul UTV or Jeep without the trailer attached.  This will require driving off road and we will also be driving off road with our trailer.  I’m equipping the truck with a fully locked rear end so we will have 8 tires pulling in the forward direction.  We also plan to build a very heavy bed to add weight to the back.  Since we are ordering dual 150 gal fuel tanks and a 217” WB with full fairings we won’t have room for tool boxes.  Our trailer has a lift kit for pulling it off road so it can accommodate a high pin height.  I’m considering building the bed from 2x10 1/4” wall steel and adding full width sliding drawers under the bed in front of the hitch.  It’s a work in progress determining hitch height too.  The steel weighs about 20lb per foot plus my decking, side fairings, bumper, gear, drawers, and bumper pull hitch.  With the bed and fuel we should be in the area of an additional 8k lbs over the rear axles.  This will also lower the center of gravity of the truck which is never a bad thing. 

I plan to use this truck a little different than most people on here.  We have no desire to stay in campgrounds all the time keeping the wheels on the pavement.  We expect to have the truck in situations most would never consider.  I used to build custom rock crawlers and we still off road with our Jeep and UTV’s and want to continue to enjoy that lifestyle.  We are trying to build the truck in a fashion that will mitigate the risk of getting stuck while performing well on the road.  We are also exploring self recovery options if anyone has any experience with that.

The main point in the hitch question was to get some real world and scientific evidence on the difference in handling characteristics based on hitch location.  When you single your truck you have created a fulcrum and the further back you move your hitch the more weight is removed from the front of the truck.  We are trying to find a happy medium and keep the weight distribution more equal and still have it maneuver well in tight spaces.  We stay in campgrounds occasionally and it seems most campgrounds aren’t equipped for big rigs.  

I might be looking at the hitch placement completely wrong and that’s why I joined the forum to get advice from those with experience.  I feel like I’m coming at this from a different angle than your typical RV hauler and that might be a good thing or a bad thing.  We can all learn from each other.  I’m trying to accomplish the shortest rig possible with the best turning radius, off road traction, and on road handling possible.  

 

[dennisvr]

I know what you mean about traction or lack of.  Mine is singled and no locker.  I think it would get stuck if it just got close to a grass area.  I too boondock 99% of the time and really have got to watch out where I can go.  I carry a Smart car so if I don't know the area I unload it and scout around.  Best wishes on your build and you came to right place to get all different ideas........
Back to your OP about hitch placement.  Mine was over the axle when I bought it and then I extended the frame and moved it back about 30" to accommodate for the Smart car.    I think its worth being 2 1/2' longer to get the improved backing. 

 

Edited January 19, 2021 by dennisvr
spelling

[Sculptor]

23 hours ago, Overthinker said:

It seems 99% of the HDT’s have the hitch behind the axles which makes no sense to an old farm boy.  I was alway taught to install my hitches just in front of the rear axle.  With practically everyone placing their hitch well behind the axle, I would really like to have a better understanding of the rational as well as the pros and cons.

I’m really concerned about overall length and weight distribution.

The search function can bring up a lot of unrelated results.  I remembered the discussion has been done a few times.  I put together weight balance with no quotes, then restricted to this forum and titles only.  This link should open the same results I got.  The members in the last topic post are Well known for the expertise they have, I didn’t look at all 7 results but assume there is good info there also.  I don’t pretend to understand the discussions I found, just passing this along for the value.
https://www.rvnetwork.com/search/?q=Weight balance&quick=1&type=forums_topic&nodes=32&search_and_or=and&search_in=titles

Particularly note the mention of a spreadsheet, which may be still available for download.  It has a pdf extension which must be changed to xls.  Mark Bruss refers to the resource guide which is always a great source.  I didn’t follow to check it.

[Overthinker]

3 minutes ago, Sculptor said:

The search function can bring up a lot of unrelated results.  I remembered the discussion has been done a few times.  I put together weight balance with no quotes, then restricted to this forum and titles only.  This link should open the same results I got.  The members in the last topic post are Well known for the expertise they have, I didn’t look at all 7 results but assume there is good info there also.  I don’t pretend to understand the discussions I found, just passing this along for the value.
https://www.rvnetwork.com/search/?q=Weight balance&quick=1&type=forums_topic&nodes=32&search_and_or=and&search_in=titles

Particularly note the mention of a spreadsheet, which may be still available for download.  It has a pdf extension which must be changed to xls.  Mark Bruss refers to the resource guide which is always a great source.  I didn’t follow to check it.

Thanks for the info, I’ll check it out.  I don’t understand all the info either, just a farm boy trying to figure things out.

[Lance A Lott]

I used 1/4 by ten flat stock for much cross members on my bed it gave me 1.5 inches more space between cross pieces, it has worked out fine so far. I singled short and put my gooseneck ball at 48", I would need to go measure to be accurate,  behind the center of the axle then I decided to carry a Smart so I made a second ball 1 foot back. I saw no negative affect doing this. It is amazing how much better the trailer tracks with the hitch well behind the axle. 

You seem to be concerned with the trailer weight shifting the load to the rear, if I read correctly,  a 6k pin weight 5 feet behind the center of the rear axle is going to lift approximately 6k 5 feet in front of the center of the rear axle 3k at 10 feet 1500 pounds at 15 feet and 750 pounds at 20 feet. I run about 8k on my front axle loaded. What surprised me was how much weight the rear axle was adding to the front axle I have the figures some where lol. 

[Randyretired]

I would like to throw out some thoughts.  Our truck is tandem because of the weight of carrying a car and RZR.  We also spend our summers in the Colorado mountains and rarely in campgrounds.  Tandem axles are a pain in uneven ground.  I have found the need to lock up just because the ground is uneven.  The lockers will pull through but if it wasn't tandem it seems it would not require locking up as soon.  The added flotation of the tandem axles may help in some situations but the ability to dig in with fewer tires is a plus in others.  

Unloading the front axle some has been a good thing for us.  By placing the hitch 5' behind the original frame it puts the center of the tandem axles (the fulcrum) about 9' ahead of the 6,000lb pin weight.  The heavy front axles inherent on semi's is not good for off road conditions.  A lot of trucks are designed to carry around 12,000 to 13,000 on the front axle and 38,000 on the rear axles.  This is roughly 1/3 of the weight on the front axle.  Many of the commercial trucks running around are loaded in this fashion.  Our truck unloads the front axle and it drives and rides just fine.  I also tow other types of trailers to carry the backhoe, skid steer and dump trailer.  The dump trailer is designed for light pin weight and still carry about 21,000 pounds.  With the light pin weight on this trailer the traction suffers noticeably.

[Overthinker]

2 hours ago, Randyretired said:

I would like to throw out some thoughts.  Our truck is tandem because of the weight of carrying a car and RZR.  We also spend our summers in the Colorado mountains and rarely in campgrounds.  Tandem axles are a pain in uneven ground.  I have found the need to lock up just because the ground is uneven.  The lockers will pull through but if it wasn't tandem it seems it would not require locking up as soon.  The added flotation of the tandem axles may help in some situations but the ability to dig in with fewer tires is a plus in others.  

Unloading the front axle some has been a good thing for us.  By placing the hitch 5' behind the original frame it puts the center of the tandem axles (the fulcrum) about 9' ahead of the 6,000lb pin weight.  The heavy front axles inherent on semi's is not good for off road conditions.  A lot of trucks are designed to carry around 12,000 to 13,000 on the front axle and 38,000 on the rear axles.  This is roughly 1/3 of the weight on the front axle.  Many of the commercial trucks running around are loaded in this fashion.  Our truck unloads the front axle and it drives and rides just fine.  I also tow other types of trailers to carry the backhoe, skid steer and dump trailer.  The dump trailer is designed for light pin weight and still carry about 21,000 pounds.  With the light pin weight on this trailer the traction suffers noticeably.

Your point brings me to another question that I have been pondering.  Would it be best to have the ability to lift one of the axles?

[Randyretired]

I am not familiar with drive axles that lift.  Is that possible?  For off hwy use it seem the lift axle would need to lift pretty high.

[Overthinker]

18 minutes ago, Randyretired said:

I am not familiar with drive axles that lift.  Is that possible?  For off hwy use it seem the lift axle would need to lift pretty high.

Let me check with the dealer again but I’m almost sure its an option even in 6x4 configuration but I’m easily confused😀