Electric Bike Motor Comparison: Hub, Mid Drive, & Friction Drive
Feb 17, 2015
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Here is a comparison of the different electric bike motor systems to help you determine which configuration is best for your riding needs.
In this article there are the pros and cons of each system: the hub motors (front and rear), the mid drive motor, the friction drive motor, and the rocket drive!
First of all, let’s take a look at the popular hub motors.
Hub Motors
Hub motors are electric motors that are housed inside the hub of either the front or rear wheel.
These are the most common motor that you will find on an electric bike (although mid drives are becoming very popular in certain markets).
There are direct drive hub motors that use the whole hub shell as the electric motor. And there are geared hub motors that have a smaller internal motor with planetary gears that drive the hub shell. Here is a comparison of direct drive and geared hub motors.
In addition, there is an emerging number of all-in-one hub or wheel systems that house all of the e-bike components (motor, battery, controller) in the hub or wheel.
Here is an overview of front hub, rear hub, and all-in-one hub motors with their pros & cons.
Front Hub Motors
Geared front hub motor on the IZIP Compact folding e-bike.
In general a front hub motor pulls you and it creates an all wheel drive e-bike.
Pros
- It creates an all wheel drive bike because the motor drives the front wheel and you can power the rear wheel with your pedal power. This can be advantageous for riding in snow or in sand. Some fat e-bikes are coming with front hub motors to create this all wheel drive system.
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Shimano Alfine internally geared rear hub and Gates Carbon Belt Drive on the Faraday Porteur.
Any type of bike drivetrain (gears) can be used: traditional gears with cogs, chain and derailleurs or internal geared hubs (IGH) with a chain or belt drive.
- Front hub motor systems are easy to install or remove from the bike because there are no gear systems to deal with (chain, derailleur, etc.) when compared to a rear hub motor. This is handy for fixing a flat tire or adding/removing electric assist from a conventional bike.
- Front hub motors can provide for a more balanced bike weight distribution if the battery is mounted in the middle or back part of the bike. This helps when lifting the bike onto a car rack or carrying the bike up stairs.
Cons
- Some riders do not like the feeling of being “pulled” by the motor.
- Since there is much less weight over the front wheel there is a tendency for the wheel to spin when accelerating on roads that have a layer of loose material (dirt, sand, snow, etc.) or when climbing a steep hill. This is more noticeable on the powerful and torquey front hub motors. I have found that after some time spent riding a front hub motor, you get used to this characteristic and adjust the assist and/or place more weight over the front wheel to work with these conditions.
- Front hub motors generally have a throttle and/or a cadence sensor pedal assist. It is rare to find a torque sensor based pedal assist system for a front hub motor.
- The front hub motors generally are focused on the lower power range (250 watts to 350 watts). There are higher powered front hub motors but they are not as common because the front fork of the bike does not provide as much of structural platform when compared the frame of the bike (rear hub motors).
- Front hub motors generally need a sturdy fork, especially for the higher powered motors. This is very important if you are installing a front hub motor kit on a conventional bike. Check with the kit company for their recommendations on what is required for the front fork. If you are buying a complete e-bike with a front hub motor, then the company selling the complete e-bike has most likely done their homework and supplied an adequate front fork to handle the motor’s power.
- They have a tendency to “bog down” on long steep climbs. See mid drive motors for climbing long and steep hills.
- The higher torque hub motors (generally the more powerful) need larger spokes and sturdy rims.
Rear Hub Motors
Geared rear hub motor on the GenZe Sport e-bike.
In general rear hub motors push you and they offer a wide range of power level options.
Pros
- Most people are familiar with the rear wheel driving the bike forward because that is the way 99.99% of bikes are built.
- There is significantly less tendency for the rear wheel to spin on loose road conditions because the majority of the riders weight is over the rear wheel.
- There is a wide range of power options (250 watts to 750 watts and beyond) because the bike’s frame provides a good structural platform to handle high torque from the motor.
- Rear hub motors can provide assist with a throttle and/or cadence or torque sensor pedal assist.
- Some direct drive rear hub motors provide regenerative braking.
Cons
- Rear hub motors are a little more cumbersome to install or remove because the gears (chain, derailleur, etc.) need to be worked around.
- They have a tendency to “bog down” on long steep climbs. See mid drive motors for climbing long and steep hills.
- Bikes that have a rear hub motor with a rear rack battery are back heavy and that can affect the handling of the bike. Some riders may not notice this if they are riding in a more cautious manner vs. a performance riding style. Back heavy e-bikes can be hard to handle while lifting onto a car rack or carrying the bike up stairs. Removing the battery can help with this.
- The higher torque hub motors (generally the more powerful) need larger spokes and sturdy rims.
All-In-One Wheel Motors
FlyKly Smart Wheel all-in-one electric bike wheel.
The all-in-one electric bike wheels house everything in the hub or wheel; motor, battery, controller, etc.
These systems come in either the front or rear wheel configuration and in general the pros and cons (see above) for each configuration apply. Here are some pros and cons for the all-in-one systems.
Pros
- In general they are touted as being easy to install or remove because it involves the replacement of either the front or rear wheel along with installation of a few other components.
- They keep the looks of the bike pretty clean. Some people may not recognize that it is an electric bike.
- Some of these systems have smartphone integration that provide a wide array of features: adjusting the settings, tracking rides, locking the wheel, etc.
Cons
- Repairing and/or replacing components of the system may be more difficult when compared to traditional electric bike kits. The wheel may need to be sent back to the company for service.
- Some all-in-one systems have just one size of battery pack. Some traditional electric bike kits have the option to increase the battery size for more range.
- Housing the battery so close to the motor can expose the battery to excess heat that can affect its range and lifespan. Some all-in-one systems may have a design that minimizes this issue but that will need to be evaluated on a system by system basis.
Mid Drive Motors
Bosch mid drive motor on the Haibike FS RX electric mountain bike.
In general a mid drive motor powers through the drivetrain (transmission) of the bike which enables the motor to help with long & steep climbs and power up to high speeds on flat roads.
Pros
- Mid drive systems are known for being able to climb long steep hills because they can leverage the lower gears of the bike and keep their rpm’s in an efficient range without getting “bogged down” like a hub motor. This is a good feature if you ride in areas that have consistently long and steep climbs.
- These motors can also leverage the higher gears of the drivetrain to cruise along at high speeds on the flat or inclined roads.
- Since the motor is at the cranks of the bike it provides for a low and centered weight distribution. If the battery is mounted in the center of the bike that further adds to great weight distribution which is good for the handling of the bike as well as making it easier to lift onto a car rack or carry up stairs.
- Removing the front or rear wheel is easy because there are no motor wires or hardware to remove (compared to hub motors). The bike can use almost any wheel type along with quick releases front and rear.
- Most mid drive systems use a chain, cogs, and derailleur drivetrain. Some systems are compatible with internally geared hubs and belt drives. The E2 Drives combines the mid drive motor with a “gearbox” at the cranks.
- There is the ability for a mid drive system to use a throttle and/or cadence or torque sensor pedal assist. Some mid drives are pretty sophisticated with sensors that measure the pedal power, wheels speed, and crank speed to provide assist that blends with the riders power to create a very intuitive ride feel. There are also sensors that will reduce power when the system senses that the rider is going to shift gears to make the shift smoother. In addition there are some mid drives that are integrating with electronic shifting systems.
Cons
- Since the power is being transferred through the drivetrain of the bike there can be more wear applied to the drivetrain components (chain, cogs, derailleur, etc.). The higher power systems will add significantly more wear and those components may need to be replaced on a more frequent basis.
- To keep the mid drive motor operating efficiently you need to be shifting the gears properly for climbing hills or cruising along the flats. If you are used to shifting the gears properly on a conventional bike then this is nothing new.
- Some mid drive systems can sense when you are going to shift the gears and they will reduce the power for a smoother shift. There are some systems that don’t have these sensors and that can lead to abrupt shifts when the motor is applying full power.
- A majority of mid drives have a single chainring which limits the gear range to a rear cogset or to the gear range of an internally geared hub. For most riding conditions this is okay because the motor makes up for the gear range that is missing and the gear range of a rear cogset or IGH is pretty wide these days.
- Most of the popular mid drives systems are only available on complete e-bikes with specific frame mounts. There are not many retro-fit mid drive kits to choose from right now but it seems that there may be more on the horizon.
Friction Drive Motors
Rubbee friction drive motor.
In general these motors have a roller that sits on the bike wheel and uses friction to transfer the power from the roller wheel to the bike wheel.
Pros
- A friction drive kit can work on a wide range of conventional bikes and some kits offer quick installation or removal.
- These tend to be relatively simple systems that may have the advantage of less things to go wrong.
Cons
- Friction drive systems don’t work well in wet weather because the friction element diminishes.
- Most systems don’t work well with really knobby off road tires.
- Some of the friction drives are not as aesthetically “clean” when compared to other systems.
Rocket Drive
Gotta throw some humor in here! Maybe we should skip electric and go for rocket powered bikes. This guy rockets to 207 mph and leaves a Ferrari in his fumes on the race track. Yes, he is absolutely crazy!
I hope this summary of the pros and cons of the different electric bike motor systems has been helpful with clarifying which system is best for your riding needs.
-Pete
P.S. Don’t forget to join the Electric Bike Report community for updates from the electric bike world, plus ebike riding and maintenance tips!
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[…] For a list of pros and cons, here is an article that compares mid drives to hub motor and friction drives. […]
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[…] kit or a hub motor? (For a relatively concise website that breaks down the differences, head here. Maybe I should have got the rocket version?) Anyways, by the time I thought I had the answer, […]
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[…] Here is an article that compares hub motors, mid drives, and friction drives. […]
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[…] Electric bike drive systems are divided into […]
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One Con missing from from Rear and Front hub motors e-bikes is the frequent damage to rims (spoke pulls) due to high torque of electric motors. Also I prefer good mechanically (non hydraulic) Avid BB7’s Disc brakes easier to service and or repair on long hauls. Why disc brakes? E-bikes using a motor cause (Heat & Friction) wear and tear on Rim Walls, traditional rubber rim brakes will cause extra wear and tear possibly causing instant rim /wheel collapse, rather replace disc pads more frequently than rebuild wheels.
Hmm. Dubious physics there.
Equivalent torque applied at the center by a mid drive is by my reckoning, worse that a hub motor because spokes are longer and therefore weaker.
But yes it seems re brakes. It came as a shock to me when it dawned on me that rim brakes wear rims, just as disk brakes wear much more easily replaced disk rotors.
well, im not doubting your own experience, but in my 8 years of riding my two ebikes (hub motors, front) I’ve never ever experienced any rim problem.
It’s far more likely that the torque at the axle is gonna cause a ‘tear out’ failure … Against that are the thick (1/8″ stainless steel ) torque plates .. Still going strong at several thousand miles per year for each bike ..No failures.
(both are eZee’s , diff models, with 350w motors )jon
I would like to suggest that in fact that braking in all vehicles absorbs far more power and stresses parts, like frames/forks and axles/spindles to a greater degree than a hub motor. That said, I wonder if an ideal arrangement would be that of one mid and one hub motor, the latter for exclusive use as a regen brake to extend battery life between charges.
I would like to take out an insurance policy on the guy with the rocket bike.
Hello everyone, I’m just looking at e bikes currently and think a mid drive would suit me for what i need and local terrain. However… I wondered if it was possible/practical to fit a front wheel drive motor in addition??
Any comments appreciated,
Dave
The quick and dirty answer is yes. two controllers, share battery, 2 throttles seems simplest, a twist and a thumb throttle should be usable concurrently
there are i think, dual motor controllers, but i think i prefer the above rig.
I like the idea a lot too. Use the front to get rolling and spare the chain jerk.
A no brainer methinks are the 2 speed hub motors. double the cost at about $120, but seem very good. I forget the name, google it.
hope it helps, good luck
I have been thinking that it might be cool to have all 3 drive systems 1 front hub , 1 rear hub, a mid drive, how ever I don’t know if I ill need a battery for each system,…..
I guess I could do a FllyKly fromt wheel and a Copenhagen wheel in back each of which are self contained systems and then a BaFang’8fun mid drive,of course I can then get a push from a trailer,then in theory
I won’t need to peddle,I’m just along for the ride!!
one aptly specced battery for multiple motors is fine.
each motor having its own controller and throttle is simplest.
I would like to talk to bikers using.the Flykly wheel in the USA. Does anyone know the correct app for the wheel? I have one but cannot find the app to run it.
very interesting and educative your comparison
however I was looking for pros and cons behind the seat VS in the frame (towards the front wheel) batteries
from what I see behind the seat are smaller, front version would favor better weight distribution
Physics is clear on this. Central and low is ideal for balance and spreading bump shock evenly between wheels/tyres/suspension.
A back rack battery is an appealing location if not destabilizingly heavy or stressful on the rear fork. U have to test ride one to see, but allow for the very real chance of needing a bigger battery than the crap usually supplied with otherwise ok bikes
should that happen, rewiring etc. for a newly located battery will be a pain.
So ideally, u cant beat the diamond frame of the traditional mens mountain bike – ~lots of space to locate, ideally, as above, yet also ideally engineered for strong and light..
A factor is most prefer main power wires as short as possible to minimise resistance/cable gauge.
In theory, u could have a battery on front pannier racks. I wouldnt as the front seems far more vulnerable to pot hole shock.
“Some all-in-one systems have just one size of battery pack. Some traditional electric bike kits have the option to increase the battery size for more range.
Housing the battery so close to the motor can expose the battery to excess heat that can affect its range and lifespan. ”
AHOULD BE
“ALL all-in-one systems have VERY LIMITED size of battery pack. Some traditional electric bike kits have the option to increase the VERY LIMITED battery size for more range.
Housing the battery so close to the motor AND CONTROLLER, WILL, NOT CAN, expose the battery to excess heat that WILL affect its range and lifespan. ”
The whole notion sucks, as any non newbie ebiker rider would attest.
Dont even think about it, no matter how cute u think it is.
Functionality and minimalism is beauty in ebikes, not aesthetics.
Dumb is never a cool look.
Fundamentally, unlike ICEs, the most limiting and ~expensive part of a good ebike is the total amount and the rate at which fuel can be delivered to the motor. Ie, the ebikes battery specs. Recent advances in batteries have made the marriage of very old and only incrementally altered tech into a world beating device for mankind.
Despite this progress, an analogy would be a car which is often, depending on battery type, only getting a trickle of gas after half an hour, and out of gas in an hour of busy use, no matter which battery type.
Limiting options in size and format in this rapidly evolving and fraught factor is the #1 thing u should not do in my view.
(lets use a simple reference of 1000 kg & 80kw, ~= a toyota corolla)
If I am ever able to ride again I will be using a ”Mid drive or a Bottom Bracket drive but a more customized style of my own design,utilizing the whole range of the 21 speeds available, I’d put more down about my design but I don’t have my patient on it yet but I get FULL use of my 21 speeds form something similar to a BaFang 8fun except I have 3 chain rings in front rather than just one!!
I’ve done somewhat the same thing. I build my own tadpole trikes and have a second bottom bracket behind the seat. That bottom bracket is actually a jackshaft with 4 sprockets on the right and another one on the left side with a freewheel driven by (in my last build) twin 500w 24v scooter motors mounted behind the seat along with the batteries. So I have 3 sprockets up front, 3 in the middle and 7 on the rear wheel. 63 possible selections ( a lot of overlap though) with either 500w or 1000w helping depending on what I’m doing. That trike could haul a lot of load in the lower gears with both motors! I didn’t have it setup to regen though. I wanted to be able to pedal without the motors if I didn’t want to use them.
I use a ridekick trailer on a home-made nomad trike. It is not as powerful as I would like but it helps.
The problem with all electric assist is that the bike gets too heavy to ride without assist. Then when you break down on the road (you WILL break down on the road) you are helpless.
I have a Bafang Mid-drive motor it run at 48Volts with an 11 amp hour battery. It’s fitted to a Giant hybrid bike . To give people an idea of how reliable it is I travelled over 8000 kilometers last year without any problems. I used three rear tyres and 3 sets of Disc brake pads. I have fitted hydraulic disk brakes. At 5000k I replaced the chain and rear cluster just because I want it reliable due to the fact I often do trips in excess of 60 kilometers and don’t want to breakdown 30 kilometers from home. I also live in a very hilly area. I ride in all weather I have fitted a watt meter so I can monitor the amps left and how many watts I am using. Only once after 70 kilometers did it warn me low battery I do pedal all the time and use the motor a little bit often I think this helps me with my distance. I love riding the bike since I have brought the bike it is saving me nearly $50.00 a week in petrol so it has paid for itself and I ‘m .much fitter and healthier.
I think we should do a Million Man eRide through NYC. Just saying.
There has been a fairly significant increase in the quality of components since 2016, 2017. . Certainly for the first time buyer, on bikes in the $2000 range.. Would like to see more updated feedback from EBR People. . Thanks for all the great input‼️
K have a frount wheel hub electric motore system with a throttle control and I live it , Large battery in mid section.Its is the best bike I’ve owned and I’m 57.Only wish it could be solar powered so it would have infaite range (the battery is the limiter). :>.
Hi Todd,
Glad you have found a good system. Here is a prototype solar electric bike with panels on the wheels.
Pete
Solar will never ever be worth the trouble on a bike. Even if the panels were 100% efficient (they are around 15% these days) the sun is too weak to do very much charging. You have to put panels considerably larger than the bike on the roof of your residence to get enough power to actually charge a bike.
I checked out the solar bike ,While it was interesting it was BS,because it is of no use because the solar bike is not available now…..he wants a usable system he can use in the present not in someones dreams,I’m sure he has his own dreams……..your answer was / is pure crap…..there is systems out there that will keep the battery charged up you just have to find one that will work 4 you seek and ye shall find………Good Luck!!