Pawl vs. Ratchet
Freehubs on bicycles are usually designed either with so-called pawls or as toothed disc freehubs. In a pawl freehub, form fit is produced with the help of coil springs. Two or more spring supports (pawls) are installed counter-clockwise in the freehub. When you pedal, they “lock” and the wheel turns. If you do not pedal, the pawls do not lock and the wheel runs freely. There are different operating principles as to how many pawls a freehub has, or how many of them can engage at the same time. The finer the ratchet of the pawl engagement, the smaller the engagement or disengagement angle. The idle travel of the crank decreases, and after rolling you have traction almost immediately again. This is especially important for time trial, mountain and gravel bikers. On a road or triathlon bike, where you are aiming for constant pedal rotation anyway, this is a less decisive factor. In this instance, fewer but larger pawls offer higher robustness and resistance against your leg force.
The second important design principle is the ratchet drive. DT Swiss and Shimano rely on ratchet drive in particular, as it promises low maintenance and a high degree of mechanical resilience. Following the expiration of a DT-Swiss patent in 2019, more and more ratchet designs are now coming onto the market. Here, two toothed pulleys are able to mesh with each other during pedalling. Unlike ratchet freewheels, toothed pulleys engage all teeth simultaneously. This ensures a very large contact area and makes freehubs very robust even with high force inputs. Small release angles, however, are not often possible.