Pyörästöön

Pyörästöön is a Finnish term used to denote the drivetrain or power-transmission system of a vehicle or machine, the assembly that transfers energy from the source to the wheels. It encompasses the chain of components that carry torque through the system, and the exact parts vary by application. In general, pyörästö includes the power source (engine or motor), the transmission, any driveshaft or belt, and the connecting wheel or axle assemblies, with a differential or other torque-distribution elements where applicable. In electric vehicles, the drivetrain may integrate electric motors, power electronics, and regenerative braking as integral parts of the same system.

In automotive contexts, the drivetrain transmits engine torque to the driving wheels while managing speed, torque, and efficiency. Common layouts include front-wheel drive, rear-wheel drive, and all-wheel or four-wheel drive, each with specific arrangements of transmission, driveshafts, differentials, and axles. Modern drivetrains often incorporate electronic control units for traction, stability, and torque distribution, improving performance and safety.

In bicycles and light bicycles, pyörästö refers to the gear system that transfers pedal power to the wheels. Typical components are the crankset and chainrings, the chain, a rear sprocket or cassette, and the derailleur or internal geared hub. Belt-drive variants are another alternative. Maintenance emphasizes chain wear and lubrication, proper tension, and checking derailleur alignment or gear-hub operation.

The term combines pyörä meaning wheel and stö as a suffix forming a system or assembly. It is used in technical Finnish writing across automotive engineering and cycling contexts.