Hub Drive or Mid Drive - Electric Bike Choices
As electric bikes become more popular, the choice of e-bikes becomes wider and the array of models on offer can at first look confusing to anyone looking to buy an electric bike - so which is the best electric bike for you? There is no one hard and fast rule, the most suitable e-bike depends on the type of riding you are looking to do, the mileage, where the bike will be stored and of course, your budget.
Does that all sound complicated? Relax, there are not as many major differences between types of electric bike as it may first seem. The one major difference is the type of drive.
Mid-Drive or Hub Motor - Which is the Best E-bike System?
Hub Drive
Currently, the most common drive system for electric bikes is the hub drive. With the hub drive system, the motor is built into the bicycle wheel and a magnetic sensor is fitted behind the crank to detect when the rider is pedalling, and how fast the rider is pedalling, in order to determine when to provide power to the motor and how much power to provide. Depending on the system fitted, some simply use the crank sensor and the level of power assist chosen by the rider on the handlebar control, to work out how much power to deliver. Some more advanced control units take into account the speed being travelled along with the cadence (how fast the pedals are turning) to determine the power needed to assist pedalling.
The hub drive engineering is simpler, but still robust and suitable for thousands of miles of cycling. The simpler engineering means that as hub motors have advanced they have become quite robust and very low maintenance, whilst keeping cost of production down. This means that most entry-level e-bikes feature a hub drive system, as well as most electric bike kits sold to upgrade a normal bike to electric. Although hub drive conversion kits are becoming more common these is a significant cost difference between the two systems.
Hub drive is a great choice for a folding electric bike as a full-power hub can be built into the smaller wheels, meaning the bike folds up as compactly as a regular folding bike, making it a perfect choice for last-mile commuting from a train station, taking along on caravan holidays or storing indoors in a compact space at home or the workplace.
Front Hub Drive:
In the early days of the electric bike, a powered front wheel was the most common solution, and some e-bikes still use a front drive. Whilst there is a certain advantage of balancing the bike weight (the heaviest part of a bike normally being the rear without the addition of a motor), drive from the front can give a feeling of being 'pulled' by the motor which at first can seem alien to a cyclist used to powering the rear wheels via the pedals and chain. Also in wet or slippery conditions the lighter load on the front wheel can lead to wheel spin, especially if setting off up a steep incline.
Due to the simplicity of installation, many electric conversion kits for bikes are supplied with a powered front wheel.
Rear Hub Drive:
As e-bike technology advanced, motors with more than adequate power could be fitted into the smaller space of the rear hub, leaving space for the freewheel or cassette of the bike's gearing system. A rear driven hub feels more natural as the power is transferred through the rear wheel, just as it is when pedalling a regular bicycle.
The stronger construction of the bike frame at the rear also means that it is more suited to the forces applied by the motor, which can cause fatigue in the lighter duty front fork mounts. A bicycle's rear triangle has been designed for power transference, so the rear is a more suitable place to install the motor drive.
Most hub-driven electric bikes now feature a motorised rear hub, with models available that retain space for 8 or more gears plus disc brakes.
Cons of Hub-Drive
- The hub drive requires a set of wires going into the rear wheel via the spindle (axle). This can make changing a tyre of tube more difficult.
- The added torque at the axle means that a heavier duty, larger wheel nut is fitted, requiring a spanner larger and heavier than the normal bike toolkit
- Quick-release wheels are not an option on the driven wheel
Mid Drive
Mid-drive electric bikes are becoming more common and often seen as the best e-bike choice and the system has numerous definite advantages. The major advantage a hub-driven electric bike has, is one of power efficiency and range. The drive system being integrated with the cranks - which is also the point of connection between the rider's legs and the bike - the power assist is able to respond to the level of power being put in by the rider, rather than simply the speed at which the pedals are turning. A mid-drive motor can respond differently to the cranks turning slowly but under pressure, such as when climbing a steep gradient, and give the boost needed to make climbing the hill easier. Likewise it can differentiate between a rider turning the cranks at a high cadence but pedalling relatively easily, and moderate the power supplied by the motor accordingly, or cut it off when it isn't needed.
This more advanced management of power distribution helps to make the mid-drive bike much more efficient than its' hub motor counterpart. With a similar sized battery, a high quality mid-drive system such as the Bosch Active Line range, can deliver an approximate range of 60 or more miles, where a 445 mile range on a hub drive may be on the optimistic side.
The system responding to the power input of the rider, also makes the mid-drive much more suited to riding on rougher terrain, such as tacking a twisty trail on an electric mountain bike, the mid-drive can give that push needed over a mound or a tree root without misinterpreting the crank speed sensor and providing too much power when you change down and cadence increases.
Another mid-drive advantage is that the electric assist system is contained around the crank, leaving the rest of the drivetrain unadulterated, using standard bicycle components. This makes it much easier to change a tyre or tube, for example, or to replace drivetrain parts when worn, or even to change out the cassette on the stock bike for one giving a different gear range - all without disturbing the ebike drive. Quick release wheels are an option, as are thru-axles and other systems dependant on the style of bike. Plus the wheelset is a standard pair of wheels making replacement of damaged wheels - something more common with heavy off-road use - straightforward, whereas a damaged rim on an e-bike means a re-build by hand onto the hub motor.
Cons of Mid-Drive
- The system is more expensive and more complex
- Control units are less likely to be generic and may need dealer-specific diagnostics as part of servicing
- Some mid-drive bikes come with frames designed to encase the drive system but on some systems especially aftermarket retro-fit mid drive motor kits, the motor can be positioned in a damage-vulnerable position especially if off-roading
In a nutshell
There is no right or wrong when choosing which drive system for your electric bike, hub drive is a more affordable entry into ebike ownership which will appeal to the more occasional rider not looking to cover large distances. For the daily commuter or rider looking to take on more challenging rides with the help of power-assist, the added range and efficiency of a mid-drive ebike will appeal. If replacing car journeys with an ebike, the initial cost is offset by ongoing fuel and maintenance cost savings. Towsure are part of the Cyclescheme network of dealers too, meaning that if your employer is registered with the scheme, its possible to both save and spread the cost via the Cycle to Work scheme.
Whichever you choose, you're sure to enjoy the assist that a modern e-bike offers, meaning less worry about how hilly your route is and more enjoyment of your time in the saddle.
