The travel chassis (also called undercarriage or chassis) is the basis of every mobile construction machine and determines mobility, terrain capability, and transportability. Basic types: tracked chassis (steel or rubber tracks), wheeled chassis (2-4 axles), and tracked chassis with flotation pontoons (amphibious excavators).
Tracked chassis offer maximum traction and low ground pressure, but are not road-suitable and must be transported via lowbed trailers. Wheeled chassis allow independent road travel (up to 40 km/h for mobile excavators, up to 80 km/h for mobile cranes), but have less traction on unpaved ground.
Specialized chassis include: walking chassis (for steep terrain, e.g., Menzi Muck), rail chassis (dual-gauge excavators for railway construction), telescopic tracked chassis (adjustable track width for narrow passages), and pontoon chassis (floating dredges). Chassis width is often critical for site access — standard passage widths of 2.5 m require retractable tracks on many machines.