Lift bars are a type of rear radius rod. Sometimes they are called "truck arms", but truck arms (as used in NASCAR stock cars) are longer and usually are angled toward each other. Lift bars generally run straight forward from the rear axle and are attached directly under or beside the frame rails. They can be any length, but if they are too short they provide a choppy ride. I like to make them at least 36 inches from the rear axle center to the front pivot point. Positioning of the bars is critical during chassis construction because they have little or no adjustment.
The good features of lift bars are their strength and their launch-ability. If they are properly built they can withstand enormous horsepower and repeated launches. Ring gears and axles will break before a properly built set of lift bars. The launch capability comes from the leverage provided by the relatively short length and rigidity; when you stomp the "loud pedal", the rear axle torque pushes the tires down against the pavement while lifting the chassis for weight transfer. I mount my bars with rubber bushings in the rear brackets so there can be some flexibility.
Rigid mounting is OK for straight-line-only racing (drag racing or salt flats), but not good for the street.
View attachment 9916 View attachment 9917