truck and trailer question

The chart gives the required landing gear clearance, but you can assume that is clearance to the lower deck. This is an old chart based on 10:00 x 22 tires. The distance from the king pin to the landing gear must be greater than the distance from the center of the fifth wheel and the rearmost portion of the outside dual tire. Allow clearance for chains if they are required.

The chart uses "fifth wheel setting", not king pin setting. Nevertheless, a fifth wheel setting of 18" will require a landing gear clearance of 63" for a single axle. The numbers for a tandem must mean a setting forward of center between the axles. In that case, a setting of 18" will require landing gear clearance of 82".

For comparison, a fifth wheel centered over the axle or between the tandems will require landing clearance of 53" and 69" respectively.

There is also a chart for trailer swing clearance for you drivers with short wheelbase. On the chart, kingpin settings are matched with kingpin swing radii.

I assume you have 108" minus 18", or 90" to play with. A tandem tractor requires 69", so you could slide the fifth wheel forward of center 21". The rig was designed for a tandem. That is the reason for the short king pin setting.

As usual, that is my opinion as a driver and I stand to be corrected.

This info came from Commercial Car Journal, July 1969, page 123.

 

I don't see a problem. The 18" kingpin set back is key. I think you have plenty of room, but select a tractor with removable mud flaps if it is close.

 

NO. The measurement is from the center of the fifth wheel, or from the pin to the landing gear.

 

With the fifth wheel centered between the tandems, the distance from the coupler to the end of the tractor frame will be about 52" depending how the frame was cut off or tapered. I estimated that from the drawn to scale illustrations on the chart.

The distance to the outside rear edge of the tires is dependent on where the fifth wheel is slid. Some tractors have a welded stop that prevents the fifth wheel from being slid behind center because it takes weight off the steer axle. The distance from a centered fifth wheel on a tandem to the outside tire is 69". Tire sizes will make a small difference. The wheel base of the tractor is irrelevant to landing gear clearance because differences in wheel base are ahead of the fifth wheel.

 

hook to it and measure b4 purchasing but it should be less than 75'