PUSHER UP
The fulcrum is measured between the drives. The wheel base is nice long, and the overhang is short.
PUSHER DOWN
The fulcrum is measured between the drives. The wheel base becomes shortened, and the overhang is lengthened.
TAG AXLE OR PUSHER AXLE DOWN
The fulcrum is measured at the center drive wheel. The wheel base is lengthened, and the overhang is reduced.
