Have you ever tried driving you car around only using one gear?
It wouldn’t be a good idea, you would probably waste a lot of fuel during acceleration and your engine wouldn’t be happy at all! But, that’s happening with most of the current eBikes and eBike Conversion Kits on the market today.
All the e-bikes that have a “hub-motor” ( or “hub wheel”, which is basically the electric motor inside the rear or front wheel ) are operating at one fix gear, which is usually designed to have an optimum running speed near the eBike’ top speed. In these conditions the hub motor needs to generate a very high torque during acceleration or going uphill which has a negative effect on the e-bikes’ battery & components by drawing large amounts of current. High peak currents should be ok for very short amounts of time, but prolonged high current will cause overheating of the motor and controller, possibly resulting in a component failure.
Most manufacturers that are looking to make a cheap eBike, will go with a hub motor solution. But, lets not be all negative about them, Hub motors do have a place in the market. If you’re looking to buy an eBike on a small budget and you just to do shorter journeys on the flat, then they’re ideal. But if you want an eBike that’s better at hill climbing, less likely to overheat and more efficient for longer journeys, then mid-drives are in our opinion, the best option.
Hub Drive Pros – Cheaper than Mid Drives and a good option if the terrain is flat
Hub Drive Cons – Draws high loads at low speeds and when climbing hills, can only deliver its full power at one speed, to remove the wheel you need to disconnect a motor
With a Mid Drive eBike solution, the bikes’ complete crank set is replaced by a motor drive unit with its own chain-set incorporated in the assembly. The motor unit will directly drive the bike’s chain as you would have done previously
By using the motor to drive the crank, it enables youto use the bike’s transmission as the motor’s gears similar to a car. By using the bikes’ gears, the electric motor can run in its optimum RPM range in each gear. This translates to a more efficient motor and a lighter better balanced e-bike. Why a lighter bike? When going through the gears, you don’t need as heavy a motor to propel you up hills, you don’t need as much capacity in your battery because a mid drive is considerably more efficient than a hub motor especially when climbing.
On the first few eBikes we converted, we used hub motors. However, since our first Mid Drive build, we haven’t built a single hub drive eBike. We believe that the Mid Drives are far more superior, which is why we don’t sell Hub Drives.
Mid Drive Pros – Good for hill climbing, more efficient, motor draw less current, motor is central and low aiding the bikes centre of gravity
Mid Drive Cons – More expensive than the hub drive and you may lose your front derailleur for a single chainring.
Each drive type has its advantages and disadvantages over the other, so its really up to the user to decide which to choose. But, our recommendation is that if you have a limited budget, want an eBike for around town, don’t plan on tackling many hills or plan to go off road, then a hub drive should suit you fine. However, if you are planning on tackling more hills or are planning on going off the tarmac, then we would suggest looking at a Mid Drive eBike.