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Old 08-12-2015, 04:35 PM   #1
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Ram Mega Cab hitch placement

I've been looking at hitch placement on the 2015 Ram Mega Cab. It seems to me that many set the pin placement at least 4" behind the Cab to Axial, CA, position. I did some calculations using this program and with the Mega Cab's 160" wheel base when the pin is placed 4" aft of the CA then for every 1,000 pounds of pin weight you take off 25 lbs of front axel weight. So assuming a pin of 4,000 the front axial will be 100 lbs lighter. I think we can all agree that 100 lbs won't effect the handling of the truck and trailer at all.

The question is how far can you safely push this? Can you push to 8", 50 lbs/1K, to get extra clearance from the cab and do it safely? Could you do 12" which is 75b/1K. what is the reasonable/saft limit?

I know that the HDT push the pin close to 48" or more behind the rear axial so that based on a 230" wheel base would be 208 lbs/1K lighter on the front axial but then a HDT front axel has over 4 times the load than does a Mega Cab.

Thoughts?
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Old 08-12-2015, 06:44 PM   #2
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With 5,900# pin I add less than 200# to front axle so you are right in the ballpark!
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Old 08-12-2015, 09:18 PM   #3
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The numbers should be right on since its basic geometry. If you're aft of the rear axial the front end gets lighter and if you're forward of it the front end gets heavier.

This calculator will calculate how much the front end will get heavier.
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Old 08-13-2015, 04:23 PM   #4
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Quote:
Originally Posted by Timon View Post
The numbers should be right on since its basic geometry. If you're aft of the rear axial the front end gets lighter and if you're forward of it the front end gets heavier.

This calculator will calculate how much the front end will get heavier.
Zactly!
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Old 08-13-2015, 08:52 PM   #5
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Quote:
The question is how far can you safely push this? Can you push to 8", 50 lbs/1K, to get extra clearance from the cab and do it safely? Could you do 12" which is 75b/1K. what is the reasonable/saft limit?
Numbers don't tell all the story of a safe good handling pin placement.
Having towed with several one ton DRW trucks pulling 18k-22k flatdeck trailers I've found moving the load point more than 2-3" behind the rear axle can have a negative effect on how the truck handles .
I used adjustable load tracks for my hitch plates much like the road tractors use.
This system allows the operator to adjust the load point up to 6" behind the rear axle and 4" forward.
With 6000-7000 lbs on the ball even at 4" behind the rear axle the heavy trailer was pushing the trucks rear on curvy roads and a braking event.
At 6" behind the rear axle truck was at the point of a jack knife with even a mild braking event on curvy roads.

Now having said all that those old trucks were the old gas 454/460 GM and Ford engines which were the top haulers of that era.
The new gen diesel adds more weight up front so that might counter a heavy trailer pushing the back of the truck around in the corners.
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Old 08-13-2015, 09:29 PM   #6
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So you've dealt with the weight. As you move that center of gravity back, you're essentially changing the point at which the trailer pushes the truck. Father back, that push is going to tend to create greater instability. Is this a problem? No idea. And yes, 5th wheels have brakes, but I know that on mine - and on many of the larger units, the trailer brakes can't come close to locking the wheels.

Curious, why not just get a slider or auto-slider?
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Old 08-13-2015, 09:40 PM   #7
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Numbers don't tell all the story of a safe good handling pin placement...

Now having said all that those old trucks were the old gas 454/460 GM and Ford engines which were the top haulers of that era.
The new gen diesel adds more weight up front so that might counter a heavy trailer pushing the back of the truck around in the corners.
This kind of discussion is what I was hoping for. Maybe some of the HDT folks might pipe in.

Considering how far behind the RA the HDTs go I suppect, as I think you do, the heavy front end is what makes towing behind the RA work. Still I don't think pushing much more than 4" behind the RA of a 3500 6.7 Cummins DRW 4x4 Mega Cab is a smart thing to do.
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Old 08-13-2015, 10:01 PM   #8
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I have never towed with a shorted or with pin behind rear axle but I think with the cummins up front 4" behind would be my personal max. Then I would have to see how it feels. I don't like to feel the trailer it literally makes me sick! I had a Trailer roll over and it's a bad feeling! I like stability.
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Old 08-14-2015, 10:45 AM   #9
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Originally Posted by cb1000rider View Post
So you've dealt with the weight. As you move that center of gravity back, you're essentially changing the point at which the trailer pushes the truck. Father back, that push is going to tend to create greater instability. Is this a problem? No idea.
I agree with the loads as all of those loads really come into play when towing a standard TT. This can require some hefty calculations to figure out.
Quote:
And yes, 5th wheels have brakes, but I know that on mine - and on many of the larger units, the trailer brakes can't come close to locking the wheels.
As far as brakes that's another huge subject. About the only way to beef up the braking is to go with a electric over hydraulic system. That's not an inexpensive upgrade.
Quote:
Curious, why not just get a slider or auto-slider?
What I'd like is a slider with air ride head but no one makes it. So the option is a slider with a TrailAir FlexAir pin box. However that said I was looking at how some of the air hitches were mounted on the HDT and what the factors were.

Since many here have used the Companion non-slider hitch on the Mega with the hitch set to about 4" aft of the RA which seems to work well so I was wondering what the issues were plus could it be pushed a little further safely.
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