Kingpin Setting

I believe most kingpin settings are shallow on flatbed because a spread axle setup takes a lot of weight off the drivers. An 18" kingpin will transfer weight from the steer axle to your drive axle right from the start. It will also give you a little more room for front overhang if that is necessary. I've been hauling oilfield production tools, and the trick was always to get enough weight up front in the winter. The good thing about a spread is you almost can't overload the back unless something is seriously unbalanced load-wise. Hope this is helpful.

 

If the front overhang on the trailer is too long, it will hit something beside the drive tires on the Tractor when you are making a tight turn.

 

Are you sure you're not reading cross member spacing? I'm pretty sure the shallowest kp setting is 18". The upper coupler always runs from beam to beam. Typically on a 102" they are ~42-50". They vary based on beam size/spacing which varies because of arch, concentration rating, etc.

The KP setting should be set for the trailer length and axle spacing for that trailer. People started messing with settings to allow for over hang especially when turning (think arc of load and corner of sleeper). For van's the settings changed as trailers went from 45 to 48 to 53. Flats have more settings available because you can order in literally any length you want, tandem, multi, or spread. Where you center the weight on a flat moves forward as you shorten the preferred setting. Which also lightens your steers and then you move your fifth wheel forward negating some of the short setting.

A decent sales person will help you through this. Most will try to sell you something in stock. The best will walk you through it and make sure you have what meets your needs.

 

Lol... We have one quad that the 5th wheel plate does not go completely under when you are locked to the kingpin. It's funny how a new driver to our company will argue the fact that he cannot be hooked up because the 5th wheel is not completely under the trailer. Had to make one guy get out and look before he broke something.

 

Most of the flatbeds I've seen are 30" kingpin setting. Some are 24". I'm in southern Missouri not far from the steel plants around Blytheville, Ar. Some people want the shorter kingpin setting so they can haul the I-Beams with more length sticking over the front to avoid having to get oversize permits for the longer beams.
The local dealer has gone to stocking 50' trailers with the 24" kingpin setting for this reason.
Personally I have not been hauling I-Beams and I prefer the 30" kingpin setting with the 48' trailer. Some of the places I go are pretty tight and barely able to get in and out with the shorter trailer.

 

Gotta remember the other reasons, not just for overhang. On that trailer I mentioned previously, I swear it is like a 10" setting... LOL But with that, I can really slide the 5th wheel forward to get more weight on the steer axle. We have some 30" kingpin settings on our stretch trailers and that really sucks because there is no sliding the 5th wheel or your drives get tangled up in the landing gear. Makes it a real pain when you are hauling a bridge beam.

 

Vans suck the trailers up close to the back of the cab. Most of us have headache racks on the back of the cab. So, you take these short hood, short wheelbase company trucks, put a headache rack on the back, move the 5th wheel foward, crunch! You tear the mudflap hangers off and you destroy the headache rack. Most flatbed guys run with the 5th wheel set all the way back. Get the drives and the trailer weights right and go. A heavyhauler will slide the 5th wheel foward to get the weight on the steers. Then again, most heavyhaul trailers will have the neck clearance to do so too. If you dont, you have all sorts of different problems.

Stepdecks will have the landing gear closer to the front of the trailer than a flat and will run a much shallower KP setting. RGNs will give you just enough room to get the 5th wheel flush with the front of the trailer so that your ramps will clear the neck when you turn. It's a juggling act. You have so much truck and so much trailer, yet you need to maneuver, carry freight, and do your best to meet the bridge laws and keep your overall length down as much as possible.

For a bunch of dumb truck drivers, you guys are pretty smart.

 

Who you calling a truck driver?