On a properly installed hitch...

Back in the day when you had to come up with your own under bed brackets and layout the 5th wheel hitch the standard was 2" in front of the centerline of the rear axle.

There is no industry standard on 5th wheel pin or GN ball placement.
When I hauled with long bed trucks I ran all my GN hitch/5th wheel pins on my long beds at 3" forward of the rear axle.
I have no idea what the hitch maker recommended.

As others have mentioned those big heavy gas and diesel engines don't loose weight like one would think.

On a short bed I run zero over the trucks rear axle. I get no front axle weight changes.
Zero over the rear axle with a rv sliding hitch gets me the full 10-12" of slide capacity behind the axle and the trailer farthest from the trucks cab.

laknox wrote:

johntank wrote:

laknox wrote:
IIRC, B&W told me that the GN sits about 3.75" in front of the axle centerline; the companion, in its most forward position, puts the king pin about 1.75" forward of the axle centerline. Most rearward position is about 4" behind the axle.

Lyle

Are you sure that you didn't get these measurements reversed?

Not for my '02 short bed Duramax, which is what I specifically asked B&W about. I can also =see= the offset, using a plumb weight.

Lyle

Thanks, as the best that I can see on my long bed Dodge it is just the reversed of your short bed.

avvidclif1 wrote:

Cummins12V98 wrote:

avvidclif1 wrote:
Figure this out. Every time I get a heavier trailer the front end weight goes down. Not by much 100lbs or so. The kingpin is mounted in front of the rear axle.

???????

Probably since your bed keeps getting lower with more weight and the angle is steeper towards the rear.

I have 5,600 pin weight and I have around 150# going to the front axle. My truck sits level with that weight.

I would agree with the rear getting lower but the airbags take care of that. Same height. Baffling.....

HA sometimes things just don't make sense.

Cummins12V98 wrote:

avvidclif1 wrote:
Figure this out. Every time I get a heavier trailer the front end weight goes down. Not by much 100lbs or so. The kingpin is mounted in front of the rear axle.

???????

Probably since your bed keeps getting lower with more weight and the angle is steeper towards the rear.

I have 5,600 pin weight and I have around 150# going to the front axle. My truck sits level with that weight.

I would agree with the rear getting lower but the airbags take care of that. Same height. Baffling.....

johntank wrote:

laknox wrote:
IIRC, B&W told me that the GN sits about 3.75" in front of the axle centerline; the companion, in its most forward position, puts the king pin about 1.75" forward of the axle centerline. Most rearward position is about 4" behind the axle.

Lyle

Are you sure that you didn't get these measurements reversed?

Not for my '02 short bed Duramax, which is what I specifically asked B&W about. I can also =see= the offset, using a plumb weight.

Lyle

TNrob wrote:
Just the geometry says some of the weight will always transfer forward, unlike a bumper pull. If the hitch is correctly installed in the bed, never ever would hitching up a 5th wheel unload the front axle. True?

This is why a bumper pull has a weight distribution bars. Transfer weight to the front tires.

Here is a forumula to calculate the weight added to, or removed from, the front axle. You need to know your wheelbase length, hitch weight, and distance of hitch from axle, fore/aft.

I'll use my F350 crew cab long bed as the example. The truck has 168" wheelbase. My gooseneck hitch is mounted about 4" ahead of the axle, if I remember correctly (I installed it about 10 years ago and I'm getting old...).

Let's say the trailer in question has a hitch weight of 3000 lbs.

HitchPosition / Wheelbase x HitchWeight = TransferredWeight

4 / 168 x 3000 = 71.4

3000 - 71.4 = 2928.6

This means that 71.4 lbs of hitch weight are added to the front axle and 2928.6 lbs are added to the rear axle.

The formula can be used for calculating bumper hitch trailers too.

Let's say the trailer has a 1000 lb hitch weight and hitch is 60" behind the axle, same 168" wheelbase.

-60 / 168 x 1000 = -357

1000 - -357 = 1357

This means that 357 lbs are removed from the front axle and 1357 lbs are added to the rear axle.

Cummins12V98 wrote:

TNrob wrote:
Just the geometry says some of the weight will always transfer forward, unlike a bumper pull. If the hitch is correctly installed in the bed, never ever would hitching up a 5th wheel unload the front axle. True?

Industry "STANDARD" is 2" in front of the centerline of the rear axle. I had always been a firm believer in that. I have wavered some on that. If you have a short bed and a heavy Cummins and 4wd I see no problem removing a bit of front axle weight by going behind the axle.

I don't think a few inches in front or behind the rear axle makes much difference, especially as you say on a diesel 4wd truck. My truck squats the same with my Andersen flipped to the front as it does when it's flipped to the back. I'm sure there's a marginal difference in the front axle weight between the two but it certainly isn't material. Now if you compare these options to moving the hitch point 4'+ back to the rear hitch in a TT setup, that's a material difference.

^^^^^No, those sound about right for my B&W Turnover Ball and Companion hitch. Definitely would be weird with the measurements reversed.