Princeton PiggyBack®
General Truck or Trailer Requirements


The axles need to be as far to the rear as possible, while leaving clearance for the PiggyBack® unit's front tires. From the rear of the truck or trailer's back tire, to the end of the bed, the minimum dimension is 33". The maximum dimension is 48".

Princeton has developed forklifts that can be mounted on trucks/trailers with the axles mounted all the way to the rear. Click here for more information.


The PiggyBack forklift needs to be installed as high as possible, to avoid contact with the ground when driving up steep inclines, ramps. Etc. The minimum distance from the ground to the bottom crossmembers of the trailer bed is 48". The minimum recommended distance between the front tires and the ground is 11". The minimum clearance between the rear tire and the ground is 18".

Princeton has various solutions for low boy trailers. Click here for more information.

Bed – Structural

Bed side and rear cross members: minimum C6 x 10.5 pounds per foot. Bed cross members: minimum S4 x 7.7 pounds per foot, 10-12" center to center.

Click here for Standard Dimensions for Straight Truck

Click here for Standard Dimensions for Trailer

ICC Bumper

This effects trailers (not trucks) manufactured after 1-26-98. When the Piggy Back forklift is dismounted, a bumper needs to be in place. Princeton offers a certified bumper for this solution, that can be folded out when the unit is not mounted on the back of the trailer.


On most trucks and trailers, the tail lights will have to be relocated. Tail, clearance and identification lights should be mounted as high as possible. This is necessary to give the Piggy Back forklift maximum clearance when mounted, and meet the minimum specifications. The tail lights should be mounted no wider than 54", outside edge to outside edge.

PiggyBack lights

Via a pig tail the rear lights of the PiggyBack Forklift are activated.

License Plate

The license plate bracket and light must be mounted such that they are clearly visible when the PiggyBack isn't mounted.