fithwheel

They make aluminum 5th wheels. Can't comment on the durability of them though.

 

You aren't going to save a lot of weight on the fifth wheel. Stretching the frame that far adds more weight than you'd save.

Best flat deck tractors are 240-270" wheelbase, mid-roof/flat top bunk with limited on-board equipment (no APU) and forward-set steer axle (Pete, KW, Starcar, etc). Most with a good tandem trailer will tare near 30,000.

 

Tare

 

Right, lol.

 

Extra frame is extra weight. The only time a flat deck driver is going to be sliding the fifth wheel is if they are pulling a 60 foot load and need the space for forward overhang. Most decks in the US these days are 10 foot splits and can load up to 40K, so weight on the fifth wheel will never be an issue.

I drive a 244" Peterbilt 379 short hood (119" BBC), 15-litre CAT, 48 inch sleeper with rack and fairings, 40K rear ends. I pull 48' and 53' high boys and step decks, Canada and Michigan B-trains and the only time I slide the fifth wheel is when I need overhang space (60 foot loads). Weight with all those trailer combinations (properly loaded) is 11,600-11,800 on the steers with full tanks and 16 chains and binders.

Half tanks tare weight with an aluminum 48' tridem is 10,900-12,500-9,000 (32,400).

My other concern about a 300" frame is going to be backing into some tight customer yards. Unlike a van, a deck driver needs to be able to back into places a van driver would be scared to ever go in forwards.