Backbone tube chassis is a type of an automobile construction chassis that is similar to the body-on-frame design. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone (usually rectangular in cross section) that connects the front and rear suspension attachment areas. A body is then placed on this structure.
It is almost a trademark design feature of Czech Tatra heavy trucks (cross-country, military etc.) - Hans Ledwinka developed this style of chassis for Tatra 11 in 1923 with the model Tatra 11. He further enhanced the design with 6x4 model Tatra 26 which had excellent offroad abilities.
This type of chassis is also often found on some sports cars. It also does not provide protection against side collisions, and has to be combined with a body that would compensate for this shortcoming.
Examples of cars using a backbone chassis include DeLorean DMC-12, Lloyd 600, Lotus Elan, Lotus Esprit and Europa, Škoda 420 Popular, Tatra T-87, Tatra T111, Tatra T148, Tatra T815 etc., as well as TVR S1. Some cars also use a backbone as a part of the chassis to strengthen it; examples include the Volkswagen Beetle and the Locost where the transmission tunnel forms a backbone.
- A Standard construction truck's superstructure has to withstand the torsion twist and subsequent wear reduces vehicle's lifespan.
- The half-axles have better contact with ground when operated off the road. This has little importance in normal on road conditions.
- The vulnerable parts of drive shaft are covered by thick tube. The whole system is extremely reliable, however if a problem occurs, repairs are more complicated.
- Modular system is enabling configurations of 2, 3, 4, 5, or 6-axle vehicles with various wheel bases.
- Manufacturing the backbone chassis is more complicated and more costly. However the more axles with all wheel drive are needed, the cost benefit ration moves in favour of backbone chassis.
- The backbone chassis is heavier for a given torsional stiffness than a uni-body.