When purchasing a bike, it is important to consider the style and amount of riding you plan to do, and then choose a bike with a frame and components designed appropriately to handle this type of riding. For example, if you plan to ride 100km+ road rides, it’s you’ll find that a Downhill Mountain Bike is not geared appropriately and is very heavy. Also, if you plan to commute on rough roads 150km/week, an entry-level recreational bike will not have the durability of a higher quality commuter, MTB or road bike.
One of the most important aspects to consider is the design of the wheels. Rim quality, number and quality of spokes and particularly the design of the hubs.
There are 2 fundamentally different geared rear hub designs; the Cassette Freehub and the Screw on Freewheel Hub. See the image attached for an explanation of the differences in design.
Screw on Freewheel Hubs are more economically priced, however they are not as durable as Cassette Freehubs. The main reason for this is due to the narrower and uneven bearing stance. You can see in the diagram that the driveside ball bearings (the connection between hub body and axle) in the Freewheel Hub are offset toward the centre of the hub. This creates more leverage between the load on the hub and the connection with the frame dropouts. Hence, Freewheel Hub axles are more easily prone to bending and snapping.
Bikes equipped with screw on freewheel hubs are not designed for riding which involves high force impacts to the wheels, including off-road use, stunting, riding off gutters, regular commuting, etc. This style of hub is inherently weak by design due to its economical price point. Hence it is only recommended for occasional recreational riding.
Bent or broken axles on Screw on Multi-Speed Freewheel Hubs are not covered under warranty, as they are inherently weak by design, hence if subjected to regular high forces will inevitably fail.
If you are considering riding on a regular basis or doing any riding that will exert significant forces to the wheels of the bike, it is highly recommended to choose a bike with a Cassette Freehub designed rear hub.