The center-engine transmits power directly onto the bike chain. Due to its position near the bottom bracket bearing the bicycle has a low center of gravity, which guarantees stable and safe dynamics and good steering qualities. A hub dynamo can easily be installed, since conventional wheels can be used at the back as well as at the front – in addition there is a free choice of gears. Disadvantages are the accessibility of the motor and the increased wear of chains and cogwheels due to the higher strain. Apart from that standard bike frames cannot be used, which results in higher costs. For a long time, back-pedal brakes could not be used in combination with centre-engines. Latest models and systems now finally offer this option – an important factor for many users.
All types of gears and all “conventional” bicycle components can be used; hardly any cabling necessary, if the accumulator is positioned in the vicinity of the motor; good position of the centre of gravity (low and in the middle of the bicycle); easy removal of wheels
Higher costs for the bike frame; the drive mounting has to be integrated; higher strain on the chain because of combined forces exerted by the cyclist and the motor
The rear wheel motor is integrated into the hub of the back wheel. Due to the power development at the back there is no additional strain on the chain and on the chain rings. With a higher weight on the rear axle this motor offers a high contact pressure and thus better traction. These qualities guarantee safe vehicle dynamics and a very sporty riding style. The front wheel can be removed easily; the removal of the rear wheel is rather complicated, though. Furthermore the entire bicycle is very tail-heavy (this may be uncomfortable when carrying the bike), long cables are necessary and hub gears cannot be used (a derailleur gear system is the only option).
Good traction, even on slippery terrain
Unfavourable load distribution when transporting luggage – especially if the accumulator is positioned at the rear, too; laborious wheel removal; extensive cabling necessary (liable to break down)
This sporty combination of motor and gears cannot be compared with conventional e-bikes or pedelecs. Compared to front and back wheel motors and mid-engines the seat post motor stands out due to its low weight (1,8 kg, including the accumulator). It is aimed at a new target group and fills the gap between the sporty rider and the e-bike. The motor unites sporty cycling with a comfortable motor support. Elegantly hidden in the seat post, it transmits the power of 200 W directly to the crank arm at the push of a button. Turing the motor on and off is easily possible even while riding. If the motor is tuned off, it works like a regular bike without resistance. Thanks to the refitting kit one is almost independent of a bicycle brand, only the frame has to have a classic shape with a straight seat pipe. Motor and control unit are integrated in the seat pipe, the accumulator is stowed in the saddlebag, and a special seat post is necessary for the cable routing. However, a seat post motor cannot be built into carbon frames.
Very low weight; the refitting of “normal” bicycles is possible; can be combined with all gear systems; almost invisible, only the large saddlebag for the accumulator and a few cables are visible.
Relatively high price; the degree of support is determined without a display
The front motor is positioned in the front wheel hub of the bicycle and powers it directly. It is the easiest and cheapest way to attach an electric motor to a bicycle. In theory, the refitting of a bicycle with an electric drive is possible, although it should be taken into account that the occurring forces might overstrain the bike frame, if it is not specifically designed for an electric bicycle. Back-pedal brakes can be used without any problems. A front motor, however, may affect the steering of the bicycle, which is noticeable during high engine performance. Another disadvantage are the dynamics of the bicycle that require getting used to in general, since the cyclist is pulled by the motor. This type of dive slips through more easily, as there is less weight on the front wheel than on the back wheel. In addition it is not possible to install a hub dynamo.
Good distribution of mass in the case of cargo bikes – motor at the front and load at the back or rather motor at the front and accumulator at the back; back-pedal brakes can be used
Extensive cabling necessary (liable to break down); laborious removal of the wheel; unfavourable vehicle dynamics in the case of powerful motors when starting up on slopes