So lets talk a little about suspension, after all, the suspension is what keeps everything stable and bring them to a halt.  When building the perfect "heavy hauler" you have to start with a good base chassis to start building.

    First off the frame has to be able to handle the weight that you want to put on it.  For this I decided to find an F-550 rolling chassis.  Weather or not to find a 4x4 chassis is still in the air.  The F-550 uses a good solid frame that is flat from the back of the cab to the rear.  This is good because I plan to cut the frame right behind the axle and add another rear section with axle.  The F-550 also uses 19.5" wheels and big disc brakes at all 4 corners (or 6 in this case :-)

    Like said before, the F-550 uses 19.5" wheels.  These have a load range of either F (3415#) or G (3750#) compared to a 235/85 16 that has a load range of E (2470#), all of these rating are for a dual configuration. Not only does this help hold the weight of the vehicle and load it also does allot for stability since the sidewalls are about twice as thick as a 235/85 16".

    As far as springs I still got a little research to do, if I stay with the leaf springs there are some good points and bad.  On the upside, it's already on the chassis, this would save me allot of time, fabrication and money to just stick with whats there.  However, with the tandem axle configuration I want to run that would put quite a bit of distance between the two axles as well as behind the last axle which could cause interference with a trailer if it sticks out too far.  Now, on the other hand, there is the option of going air ride.  Big trucks use this for a very good reason and it's not for the comfy ride.  They use air bags because with a simple leveling valve the truck will stay at the same level (front to rear) no matter what the load is. This is very important to maintaining control and managing weight distribution.  You see, as a truck "squats" in the rear a certain amount of the front axle weight is transfered to the rear (about 200# per inch of "squat").  By running air bags you also have a spring rate that is always perfect for the load.

    Now, lets get to that second axle and 4x4 option shall we?  The main reason for the second axle is of course weight capacity.  There is another benefit to the tandem setup, I will have allot more "play" as to where the fifth wheel plate will sit without having to worry about how much weight it is putting on the front axle.  This is VERY important since I am sure there will be quite a few times I end up in a scale house with a DOT agent trying to say the truck is over weight and I don't want to give him any ammunition lol.  

    How will it fit you ask?  Well let me explain, I had found an article at one time either on USA 6x6 or Ford Cummins where a they had set an OBS body on an F-550 frame.  According to the article and pictures, most everything lined up between the cab and the frame other than the core support.  They had to be cut from the frame and re-welded an inch or to back on the frame.  Now during this swap I will be adding a 1"-2" body lift, this will help clear a larger down pipe off the back of the turbo.  It will also help give the truck the taller stance I am looking for.