Constant pedalling, even when you aree going downhill, is obviously not a very practical way to cycle. This is why the freewheel was invented. A freewheel interrupts the connection between the chain and the crank, so that when the tyres rotate, the pedals do not rotate with them. But on an e-bike, freewheeling can also mean the interruption of the motor assistance. Learn more about freewheeling on bicycles and e-bikes here.
How exactly does the freewheel work?
A freewheel is a mechanism located in the rear hub of a bicycle. It ensures that the pedal does not automatically rotate in the direction of the rear wheel when it moves. In short, the freewheel decouples the connection between rear hub, chain, sprocket and pedals. This can be achieved in several ways; in the following, we will introduce you to the various types of freewheel.
Ratchet and pawl freewheel
The ratchet and pawl freewheel is the most common type. In this design, the diagonally mounted locking sleeves only catch when you pedal forward. Without a pedalling movement, these only drag without catching; this is what makes the well-known freewheeling noise.
Star ratchet freewheel
With the somewhat more complicated star ratchet freewheel, two toothed discs with slanted teeth are pressed together by means of a spring as long as you pedal. Here, the typical freewheeling noise comes from the toothed discs moving against each other when idling. Significantly more robust than the ratchet and pawl freewheel, the star ratchet freewheel is preferred for bicycles in the freeride and downhill segment.
Unlike the last two types of freewheel, the roller freewheel is very quiet. Here, pedalling presses up to eight pinch rollers against the hub and moves it forward. When the rider does not pedal, there is no pressure on the rollers. These rollers then run freely in their guide tracks, as with a typical ball bearing, and make virtually no noise.
Sprag clutch freewheel
Another variant is the sprag clutch freewheel. While in one direction of rotation the inner ring can be turned against the outer ring as desired, in the opposite direction of rotation the two rings are locked against each other by the clamping elements.