Mid-drive electric bike conversion kit
There are a lot of advantages to installing a mid-drive electric bike conversion kit on your bicycle. Unfortunately, there is also a lot of marketing nonsense that is put out to glamorize the potential of ebike mid-drive motors.
We look into why mid-drive electric bike conversion kits are so popular, despite their relatively high price tag to other e-bike conversion kits.
This article dispels the myths and highlights the advantages of fitting a mid-drive electric conversion kit to your bike.
To highlight the advantages of mid-drive electric conversion kits, we compare mid-drive motors to hub motors to explain the difference.
What is a mid-drive electric bike conversion kit?
The term mid-drive electric bike conversion kit refers to electric bicycle motors which fit in the middle of the bike. Most mid-drive electric motor kits mount the engine between the pedals. Mid-drive electric bike conversion kits are also referred to as mid mount ebike conversion kits.
Mid-drive engines can be located anywhere in the center of the bicycle between the front and rear wheels and, in more sophisticated ebikes, they can be discreetly integrated or hidden in the bicycle frame itself. Most mid-drive motors sit in the lower section of the bicycle frame between the pedal cranks and send power to the rear wheel through the bicycle chain.
By contrast, more popular, electric hub motors are positioned in either the front, or rear, wheel of the bicycle. Hub motors are integrated into the bicycle wheel itself. Where mid-drive motors require a chain to drive the rear wheel, hub motors power the bike directly through the wheel itself.
Mounting the electric motor in the middle of the bike provides several advantages, the most important of these is weight distribution.
Mid-drive motors do not clutter the rear axle of the bicycle allowing regular bicycle gear clusters to be fitted. A wide range of gears is important for many bicycle sports, especially mountain biking.
There is a further benefit of mid-drive electric motors where laws prevent the use of throttle controlled e-bikes. The pedal crank is often integrated into the mid-drive electric motor. Integrating the motor and pedals gives the manufacturer the opportunity to use pedal pressure sensors.
Mid-drive motors are often integrated with the pedal crank. Pressure sensors can be added to measure how hard the rider is pedaling. Motor management software can use information from pedal force sensors to intelligently help the rider. Motorized e-bikes then feel like regular bicycles that simply require less effort to ride.
Mid drive electric bike vs hub
- Where electric hub motors are fine for commuting and use or tarmac roads, mid-drive motors offer a better balanced bike which is important for many sports. Mid-drive motors allow improved suspension and reduced strain on the spokes of the drive wheel.
- Sensors on hub motors can only provide information about the pedal speed. Mid-drive motors can provide detail of the pedal force that the rider is exerting. The advantage here is that management software can micro-adjust the power of the motor creating synergy between rider and machine.
- Rear wheel electric hub motors take up a lot of space around the rear axle. Gear clusters have to be narrower and often limit the rider to between 3 and 5 gears.
- Hub motors become less efficient as they approach their designed top speed. Gear selection on mid-drive motors keeps the motor closer to its most efficient speed. There is, therefore, a small efficiency in battery usage which can help extend travel distance.
- Front wheel hub motors lose traction off road as there is little weight over the drive wheel. Rock hopping becomes impossible as front end weight damps the bike’s agility. A front end hub motor provides no assistance when the weight is on the rear wheel.
- Rear wheel hub motors bog in mud and slide out on slippery corners. Poor weight distribution affects the way the bike lands after jumps making them more difficult to control. Extra weight at the back can make the bike awkward, and slower to respond to rider input.
- Extra weight of hub motors hamper the ability of the suspension to absorb bumps. If the tire has less time in contact with the ground this equates to less traction for the rider.
Mid-drive motors allow manual gear selection
As mid-drive electric motors transmit power through the bicycle chain, the rider can manually select the gearing at the rear wheel. Gear selection allows the rider to intelligently select the best gear for the terrain.
Independent gear selection allows the rider greater control of the torque delivered to the road as they control both throttle and gears.
A big advantage of mid-drive motors is that they allow large, multi gear clusters to be fitted to the rear wheel. As mid-mount motors do not clutter the rear wheel in any way. This allows ebikes to provide the same range of gears that would be available on a regular bicycle. Electric mountain bikes with mid-mount motors can often offer 12 speed cassettes.
Being able to select the correct gear on a mid-drive motor will keep the motor closer to its best performance curve. Although the improvement is small, greater gear selection should help extend travel distance of the battery.
Mid-drive electric motors are not hampered by limited space at the rear axle and have no restrictions on the cassette that can be installed.
The second advantage of mid-drive motor e-bikes is their weight distribution. It is important for many bicycle sports (e-mountain biking for example) that the bike is balanced. Weight evenly spread between front and rear wheels provide more rider control and improved shock absorption.
Evenly distributing the extra weight of battery and engine between the bicycle wheels makes a huge difference in how the bike handles and performs.
Electric bikes with mid-mount motors behave like mountain bikes. The extra weight can make the e MTBs less nimble, but the power advantage offsets the drawback of additional weight.
An e bike with even weight distribution improves suspension performance. A lighter rear wheel can bounce and adjust to rough terrain far faster.
An often overlooked property of mid-drive motors is their reduced impact on spokes. E-bikes with hub motors have smaller, stiffer spokes to handle the extra unsprung weight. Shorter, thicker spokes have less flex than regular spokes that are fitted to e-bikes with mid-drive motors.
The extra flex in full length, regular spokes helps to reduce the shock that is transferred into the suspension. In addition, lighter wheels also transfer less force through the spokes. The additional flex and lighter wheels greatly reduces the frequency of loose and broken spokes.
By simply disconnecting sensors, mid-drive motors can be easily modified to allow unlimited top speed. As unrestricted mid-drive motors have external gears, their speed is only limited by rider effort.
A 500 Watt engine will have a top speed of around 25 MPH without rider assistance. Adverts that present mid-drive electric motor kits as faster, or more efficient, than hub motors, are false.
A similar power hub motor can be adjusted to provide the same speeds as an unrestricted mid-drive motor. It is often more difficult to overcome restrictions on hub motors as there can be rev limits on some designs.
Hall sensors and magnets are used to control the speed of mid-drive motors. Often, magnets and sensors are fixed to the wheel and frame of the e-bike. The sensor tracks the rate at which the magnet passes and electronic management systems calculate speed based on this information.
If you have purchased a mid-drive electric motor kit then the speed limiter is set by the user. Mid-drive motor kits require the rider to enter the bicycle wheel rim diameter. Pedelec speed restrictions can be easily manipulated by entering a smaller wheel diameter than the true wheel size.
Many mid-drive motor kits can also operate without the hall sensor fitted.
Hub motor kits do not require hall sensors to be fitted. Bike builders fit the pedal sensor in order that the motor complies with speed legislation. If the builder does not fit the sensor, the motor will only be limited by its power and design limits.
If you have purchased a brand name e-bike with a mid-drive motor, the sensors will be integrated into the motor unit.
Although it is difficult to disconnect the sensors, e-bike speed restrictions can easily be hacked by fitting a performance chip. Performance chips are available for most brand name e-bikes and are simply attached using a click fit connector.
Mid-drive motors have an added advantage when interoperating with US Class 3 restrictions or European Pedelec standard. To comply with these standards, the rider must pedal to activate the electric motor.
Top brand e-bike manufacturers are using large budgets to develop the interaction between rider and engine. The goal is to provide a seamless feel to the rider so that the pedaling effort is reduced naturally. Mid-drive motors can obtain feedback directly from the pedals. Sensors can detect pedal load (rider pedaling effort) in addition to pedal speed.
The additional sensors and more sophisticated management system can give the rider options on how the motor and rider interact. The rider can often choose the ride distance and pedaling effort to ensure that the battery does not fade early.
Mid-drive electric motor conversion kits place the electric engine in the middle of the bicycle. The engine position improves the control the rider has on the bike, while the distributed weight enhances suspension and damping making the bike more planted.
Mid-drive electric motors are a ‘must have’ on mountain bikes. Mid-drive electric bikes are more capable in fast off road terrain, and can maneuver well when rock hopping.
There are no speed advantages to a mid-drive electric bike, however, larger gear clusters can be fitted. Greater selection of gears allows the rider to keep the motor in the power curve for greater efficiency.
Mid-drive electric bike conversion kits have a premium price tag. A mid-drive electric bike conversion kit will typically cost around 30% more than the comparable power hub motor kit of similar quality.
If you want a commuter e-bike, or you simply are not into ebike sports, then an electric hub motor is every bit as good as a mid-drive motor, and a fair bit cheaper.
If you like difficult, off road trails, or like to throw your bike about, then mid-drive electric bike conversion kits are the way to go.