School me on kingpin depth

I'm guessing only; maybe because of have to install a headache rack and sometimes overhang off the front of the trailer. I've done the mudflap thing also; finally just leave them off unless bobtailing.

 

Flat beds normally have the same kingpin depth as vans do. Normally....

 

With a van you are going to be legal weights. With a flat you can be hauling overweight items. How much overweight you can be all depends on axle spacing.

Last place I worked we had two 4 axle 53 foot trailers. One I could gross 103,500 legally. On the other i could gross 105,500. This was all because of axle spacing, one had a deep kingpin and the other the front of the 5th wheel stuck out in front of the trailer when hooked up.

 

Another wrinkle will be the frame behind the 5th wheel. Sometimes there is too much frame for flatbed work. The necessary strength of flatbedding with a big coil or two is way harder to bridge than a ordinary van. A van will fail quickly under such loading. So you see the flatbed frames extending pretty much all the way to the 5th wheel plate.

Tractors set up for flatbedding have different subtle changes versus ordinary trucks. A bigger catwalk, a bulkhead chain holder and angle iron under the 5th wheel to rear plus a sliding rack for that 5th wheel to be adjusted. Sometimes there is mudflaps but usually not necessary for a full tractor trailer combination.

I would not worry or try to re-engineer what has been engineered for you. The kingpin is pretty much the strongest object anywhere on a big truck and you can bet that the engineers have already thought things through when building various kinds of trailers for specific jobs.

Frankly I like my trailers with certain things whatever they might be. But man is not infallible. So I keep a few boxes of this and that plus spares to keep trailers going a little bit.

 

That is one of the stupidest things I have read here. You really need to get out of the basement sometime. I really hope that someone does not get hurt following your advice.

 

The shorter pin setting typically 24' is usually found on a spread---not just flatbed spreads--itis for better weight distribution to axles--understanding you can go to 20k per on rears 40k vs 34--
34/36'' is more standard on higher speced vans/reefers
48' pins are typically found on fleet 53' running setback axle aerocabs--with fixed 5th wheels
but this is all a generalization.
just in terms of basic understanding

 

Most stuff, flatbeds, vans, and refeers are at 36" deep kingpin from the front of trailer. Of course that makes no sense to RGN. For tanker you better ask the guys that pull them.

Like casper alluded to, in states that allow heavier then 80k on a standard permit, lot of trailers are spec' ed at 24", "18, or even "12 to get the span between the drives and the multiple axles on the the trailer wide enough to satisfy the bridge weight requirements.

Now states like CA with KPA to rear axle laws, or overall length laws, you will find a few companies pulling trailers with a 48" or even 60" deep kingpin to accommodate the KPA requirement with a longer trailer. That stuff is mainly only for the light loads anyway.

 

I actually look for deeper kingpins to make a come back on van reefer. I think a lot of companies for a number or reasons went to 30" settings, but with fuel efficiency such a big item I look for them to move back to the 36" setting to close the gap between the cab and trailer.