5th wheel pin sizes

[LowTech]

I've heard a lot, and did a bunch of online searching, and I'm still not sure how to determine pin size and what a plate will handle. I hear about 2 3/4", 3", and even 2 1/4". Is this the length? What about dia?
How do you know what a plate will handle? Is there a way to measure the throught, depth, width, etc.?

Thanks for any info that will make this confusion go away

 

[RAYZER]

I would like to know this myself!

 

[PowerstrokeNC]

Subscribed

 

[M1075]

I believe the two diameters are 2" (standard/commercial) and 3.5" (oversize/military). On military tractors, any all wheel drive tractor bigger than a 5 ton is 3.5". Everything else is 2".

 

[Artisan]

I am inclined to go w/ M 1075's input.

But;

Is there a bushing to bush a 2" up to a 3.5" ?

Can you link me to said someplace FS on the web ?

TIA!

 

[LowTech]

When we measure dia, is that the dia of the thick part or where it hourglass's in?
And I've found that they're not all the same length. I saw one yesterday that was only 2" total length. It would not go deep enough into my plate to lock in. How much dif is there in length on mil and civy

 

[quickfarms]

There are two different size king pins.

2" and 3.5"

The 2" is for normal trailers and allows a GVW of 80K

The 3.5"'is for overweight or heavy haul.

The diameter refers to the small diameter.

The king pins need to be checked for wear periodically. There is a special wear gauge. The wear can not exceed 1/8" of the diameter.

There is a collar to convert a 2" king pin to 3.5" but it is not certified for use on the road.

You can convert most tractors with a 3.5" fifth wheel to 2" by changing the plate out.

Most heavy haul trailers can be ordered with a removable king pin to change the size.

There is also a short 2" king pin that is found on some recreational trailers. Additionally there are several other proprietary setup a that can be found on old trucks and trailers.

 

[LowTech]

Quickfarms - thank you very much. That's the kind of info I needed.

 

[two.fiveM35]

Great info, I have wondered about this myself. Thanks for the explanation