Mid Drive Vs. Hub Drive | Which motor for e-bikes is better?

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Mid Drive vs Hub Drive?

We’ll start this like Fincher’s Fight Club, the end at the beginning and then explain why.
Mid drive vs hub drive?

Mid drive takes the cake. I was going to say that it depends on your use, but that’d be too cliché.  When you really break it down, the mid drive is a clear winner. I’ve included a table below for your convenience but if you want to really understand why, continue reading below.

Mid Drive

Hub Drive

ProsConsProsCons
Greater torque = better hill climbingMore ExpensiveRelatively cheaper than mid drivesHeavy and uneven weight distribution (especially with front hub)
Overall better performanceMore wear and tear on drive-trainCan DIY with large range of ‘off the shelf’ motors.Torque arm required for high powered hub motors (front hub)
Low and centred weight distributionNot many retrofit options. Mostly proprietary motors on complete e-bikes.AWD system (front hub)Issues with climbing steep terrain
Utilises the gears, thus providing higher top speedsLess strain on the drivetrainLimited top speed

 



How the Journey Begins?

It’s a question that has been around since the dawn of e-bikes. You get an electric bike for the first time and get addicted to the boost. Three weeks after riding you’re on the hunt for more power and looking at other motors. It creeps into every e-bike rider’s mind and eventually you find yourself up at 3am reading endless threads on forums and watching YouTube videos on what’s better.
No? Just me?
Well I’ll make it easy for everybody and break it down.

Let’s begin with a little lesson on what each type of motor is to understand why mid drives are better.

Hub Drives

Hub driven bikes are commonly powered by DC motors, typically brushless as they; perform better, are more reliable, and quieter (than brushed). If you want to know how a DC motor works or the difference between a brushed and brushless DC motor, Youtube can help you with that. Find one with animations as they help illustrate how they work with more details.

Okay watched the video?

So back at it. You’ll find a typical torque and power curve below for a DC motor.

[Credit: EBN]

With DC motors, torque is always maximum at zero speed which is called the stall torque. As you can see above, the motor’s torque will drop in a linear fashion with speed/rpm. The theoretical power curve will be a parabola shape and peak somewhere in the middle. If you read my bike reviews, you’ll know that I test and dyno the e-bikes when possible. Here’s a plot of the Fat-E Mini below.

You can see that it resembles the theoretical plot quite well. There are some irregularities due to real world effects such as friction, efficiency and what not, but it seems fairly accurate. What’s important to look at here is the area under the curve, not the peak torque or power. A car or mechanical enthusiast will always tell you that a machine with more area under the curve will outperform one that has less area – especially if they produce identical peak numbers. Just remember this as we get into mid drives.



Mid Drives

With mid drives, they’re almost identical to hub motors however mounted at the bottom bracket of the bike. It directly connects to your cranks and gears. Because of this, you get a better power/torque curve. Imagine the hub drive dyno, but then add a plot for each gear like this:

Dyno plot completed for the Dillenger Hunter Off Road. Testing 2nd, 5th and 8th gear.

Yeah a little crazy, but it’s pretty much the hub drive dyno for each gear. The curve stretches out with each higher gear. Do we remember what was said about power/torque plots? It’s the area underneath the curve that really shows the performance of a machine, especially when they’re rated at the same peak power/torque.

Let’s just assume that the peak power numbers for the Hunter are identical to that of the Fat-E Mini. Comparing the characteristics of each plot, you have the mini with one power curve whereas the hunter has multiple power curves (as many as the gears it’s fitted with). These multiple power curves are essentially combined which obviously would sum up to a large area – greater than a hub drive power plot (not always true, but typically). So in terms of performance, the mid drive is a clear winner.

Power and torque Performance? Mid Drive

How do they compare in handling?

As we should know by now the mid drive is installed on the bottom bracket with the battery/controller installed on the down tube. This keeps the bike’s centre of the gravity very low and centred. With a hub drive, the centre of gravity is generally a little higher than the mid drive by offset – either to the front or rear. Using my next level professional photoshop skills, I’ve compiled a diagram below where the black and white circle label symbolises the centre of mass.

Depending on the wheel size, the hub motor could sit either higher or at the same height as a mid drive would. This results in the centre of gravity being somewhat similar in terms of height, however the front or rear hub will shift the weight, either towards the front or rear. This will affect handling, and is especially the case with the front hub. Having a 3kg wheel that you turn with, will greatly impair the handling of a bike.

Handling? Mid drive

How does the mid drive stack up against the hub drive with price, maintenance and other things?

Frankly the mid drives trumps the hub drive in almost everything but price. They are more costly and when something does go wrong, they are more expensive to fix than hub motors. Another thing to consider is that hub motors are readily available with many options on the market. These motors are also easy to install and allow retrofitting. Mid drives on the other hand are a different story.

With Bosch, Shimano and Yamaha (just to name a few) producing complex high end mid drive motors, it makes it difficult, close to impossible to fit it to your current bike. Unless you’re a frabricator who can make a custom frame, it’s most unlikely for you to be able to buy a Bosch mid drive on a weekend and fit it on your daily commuter in one arvo. There is Bafang who provide mid drive kits that fit onto the bottom bracket but even with that said, hub motors are more readily available and easier to install.

Cost and couple of other things that no one really cares about? Hub drive

Conclusion

There you have it folks, we’ve come to a full circle with mid drives taking the win in this fight. Hopefully you understand from a deeper level why mid drives are better, and share this with your friends and fellow riders! Remember the first rule of E-Biking Now is to talk about E-Biking Now.



17 COMMENTS

  1. Hub motors are almost useless. The basic problem is that (very roughly) motor torque is proportional to weight. So for the sort of torque you want at the wheel you NEED a reduction gear – with hub motors you will need two reduction gears once for each wheel. Everybody starts off thinking “hub motors are cool” – but nobody end up using them because they are usless.

    • Heya Jake,
      Are you from FLX electric bikes?
      Oh really? I didn’t know that. Cheers for explaining that for us.
      I guess that cements mid drive motors in this debate. The only thing that hub drives do have going for them is maybe 2 things; it’s simpler and cheaper. But these are changing with the progression of eBike kits. Mid drives are getting cheaper and simpler.
      – Eric

    • My 2WD 50MPH Hub motor based daily driver is pretty far from useless. Torches any mid drive , so that would make mid drives useless, in comparison.

    • Jake bull sh@@! this only works for very low powered E-bikes, try running 14kw on that mid lol, mid drives are good up to 1.5Kw max nice for slow ridding and about 65kmh bursts. An high power huby can take loads of power get some FF and Hubsinks on and run it at 6-30Kw+ and you have real fun!
      Graham.

  2. I build and service all makes of ebikes.
    Simply put, you are wrong.
    Hub motors are far more reliable, less complex, and can put far more power to the ground than any mid drive. The mid drive total power is limited by the chain and freewheel. These are drive train parts which were never designed to handle the torque of any motor, they were designed for human power (which is about 250 watts if you want to translate that to electric force). You are stressing these components far beyond their design parameters with a mid drive.
    There is more room for a larger and more powerful motor within the wheel than there is between the cranks. I don’t know where you are getting your information about lack of power from hub motors, but I can easily build a 60+ MPH bike if anybody is foolhardy enough to ride one. Climbing hills is not a problem. You speak of uneven weight distribution. Most of my customers prefer a very erect riding position to the more aggressive racing or mountain bike stance. When sitting erect the balance is pretty uneven (biased to the rear) on most any frame I know of. If the rider is very concerned with weight distribution there are very reliable, quite powerful geared hub motors available. On average they weigh about 6 Lbs. the standard bike hub (about 1 Lb.) is replaced by these, so effectively about 5Lbs is added to the front or rear wheel. If you carry your lunch in a front or rear basket you are already altering the weight bias by the same amount.
    Hub motors have far fewer moving parts, if fact a direct drive hub motor only has the stator rotating within it, and no other gears, clutches, freewheels, Etc. These motors will go thousands upon thousands of miles trouble free.
    Electric motors have full torque at zero rpm, so I don’t understand your claim of more power obtained by a gear reduction. If the motor is of appropriate size, there is no hill or terrain which will challenge the motor.
    Another thing to note is that the Bosch mid drive is not serviceable in the USA. All units are required to be returned to the factory in Germany for service. That should run up a pretty hefty shipping bill (more than the cost of a hub motor) and require a pretty fair amount of time when the unit needs to be repaired. I’m not aware of other manufacturers repair or parts policies.

    I believe it’s a no brainer, the hub motor makes far more sense. You write this article as an expert, but clearly you do not have the experience and information to write an in depth article about this subject.

    • Heya Shepherd,

      Welcome to the site and thanks for your input. It’s great to see that I’ve created a discussion which allows us to clear things up with experiences that different people have had.

      Firstly, with your point that hub drives are more reliable and less complex, I completely agree. I did state that in the article, not sure if I was clear on that or not (my apologies).
      I can see where you’re coming from with the rest of your points such more power to get up a hill and the added drivetrain stress. This article was written as a general comparison between the two types of motors, towards the more general consumers interested in eBikes, and whom would most likely want something not so ludicrous.

      So when comparing a general hub motor and a general mid drive motor, a mid drive motor would outperform a hub drive on hill climbs without a doubt. Do you agree with me there?
      I won’t deny the fact you can get a hub drive motor that can get you up a hill, but to match the hill climbing performance of a mid drive, you’d need a higher output motor yes? It makes sense, otherwise high end electric bike companies (no matter if it’s commuter or eMTB) wouldn’t use a mid drive system. If you look at Haibike, Kalkhoff, Riese and Muller etc., they all use mid drive motors.

      Like you said, there is added stresses to the drivetrain which I also mentioned in the article. However typically speaking when a cassette, crankset etc., are designed, they are designed with engineering safety factors such that they can withstand forces greater than typical usage. But even with that, I agree there still is a lot of stress on the gears and I have seen quicker damage to it. To combat this, bike manufacturers and riders could use the SRAM EX1 drivetrain. These are designed for eBikes and are more robust.

      Your point on the weight distribution is fair for rear hub drives that are compact. Anything large or if equipped on the front hub, the balance of the bike would change significantly.

      Yes electric motors exhibit maximum torque at stall RPM like I mentioned in the article, however I wasn’t clear with the power statement. With mid drives, you can actually change your torque value. With hub drives the maximum torque you’re receiving and going to output to the ground is fixed to whatever the motor is capable of. Since a mid drive uses the gears on the cassette, a change in the ratio of the cassette or chainring can increase torque and power. Using a 11-42t cassette will obviously output more torque to the ground than a 11-36t cassette. Same deal with the chainrings. As for power to the ground, if you get a 250W hub motor and a 250W mid drive motor on the exact same bike and ran a dyno test, the 250W mid drive motor will have a greater power band.

      As for servicing Bosch motors in Australia (we’re Australian based), I think we have a service centre locally. Regardless there is still shipping and more costs, which I also did mention in the article.

      Simply put, the mid motors are generally a better performer, whereas hub drives are more reliable and cheaper. It depends on what the rider is looking for, and I was going to answer this article with that answer, but like I said it was a little too cliché.
      I never mentioned I was an expert, however with an engineering background, it does help me understand the mechanics better which I attempt to explain to the general audience.

      Cheers,
      – Eric

  3. Lots of falsehoods here. Clearly you have no experience with direct drive nor understand electric motors in general. You missed disadvantages of the mid drive and advantages of direct drive.

    Clearly someone has not tried good setups of both ( they both have their merits )

    • How you doing Neptronix?

      I have had experience with both electric motors, and from my experiences the mid drive was a better performer. Even with facts and numbers, mid drives out perform the hub drive hence why the performance eBikes regardless of a commuter or eMTB use mid drive systems.

      Can you elaborate on the disadvantages of the mid drive and advantages of the hub drive please? I may have missed some, but my table does show that both have their merits.

      Thanks,
      – Eric

  4. I am not sure when this article was written but it is September 2017 & a lot of the information is now outdated. First of all your article has assumed that for comparison purposes everyone is riding a Mountain style Bike which are not exactly the optimum choice as a comparison vehicle. With 27.5/29 or 700 size wheels of course your center of gravity is going to be higher & weight distribution will have a greater affect on your handling, braking & acceleration. Use a Recumbent trike, Folding or Delta Upright trike & your results & numbers would be significantly different. As for Crank Drives (Mid Drives are technically something different) there are also varieties that would skew your results as would the use of Direct Drive or Brushless, Geared hub motors. I think it is an error to try & make a Blanket Statement that ALL Crank Drives are better than ALL Hub Motors. Some are but but some Hub Motors offer power & reliability that will exceed some Crank Drives. For rideability & smooth power application Torque Sensors are hard to beat & they can be used on a hub motor or Crank Drive.

    • Hey Glen,

      Welcome to the site EBN! It was written at the beginning of the year, so it was a while ago.
      Yes I did make the assumption everyone was riding a typical modern bike, commuter or mountain bike.
      I apologise for not including a recumbent trike, however the article is titled “Mid Drive Vs. Hub Drive – Which motor for e-bikes is better?”. So obviously it wasn’t taking into consideration trikes.

      I did mention in the article that the hub motors do offer reliability, however wattage for wattage, a mid drive will output more usable power and torque than a hub drive. Hence the blanket statement. But yes, a blanket statement is never the best answer, but it does offer some riders a more simple answer. But thanks to comments like this, we’ve created discussion and readers can see the other perspectives and make their own judgement, which is what we were aiming for.

      Thanks Glen,
      – Eric

  5. Hi Eric, and thank you for your article and discussion board. I doubt that my credentials merit my post, as I am not an engineer by any stretch of the imagination. In fact your colorful charts mesmerized me, like shiny objects to gorillas. My only qualification is my over 18,000 miles of experience over the last 3 years: I have owned 8 different ebikes, mostly hub motors. When I was able to afford my first low-end Transx mid-drive, I was defiantly a fan. When I upgraded to a Bosch, I was thoroughly converted and drew my “line in the sand” to anyone who even mumbled the word “hub-drive”. But then something happened and, once again, my thinking was reversed. The experience that led to my resurrection can be summed up in one word: Stromer, more specifically, Stromer St2s. I commute 34 miles to work each day, no human-powered vehicle has yet to pass me, even the mid-drive boys. And sometime, when I’m pedaling hard enough (Stromers don’t have throttles), I keep up with cars. My Haibike sits in my office and is my “backup” in case anything happens to the Stromer. Needless to say, it hasn’t. In fact, my Haibike has let me down more times than not. Don’t get me wrong, the Haibike is a good bike and Bosch makes a great mid-drive. . . . But the Stromer. . . well you’d just have to ride one to find out. Unfortunately the simplistic artistry of a well engineered direct drive is a dying breed. And I welcome a mid-drive that can accomplish what my Stromer does now. Specialized has already ditched their direct drive, and I almost want to try one of them, before they become extinct. In terms of hill climbing, I do a 7% incline for two miles at 30mph pure pedaling, again, no mid-drive can touch me, either at the beginning or end of the hill.

    In my humble opinion, I don’t think the debate is “mid-drive” or “hub-drive”; instead the debate should be more complex; Hub-drive or mid-drive does not the e-bike make. . . . it’s all about design. Thank you for your tolerance.

    • Hi Jan,
      Thanks for your comment. I must say, it’s probably one of the most civilised response I’ve had on this topic haha! You having that much experience and 18,000 miles on eBikes definitely adds legitimacy to your argument. However there are a couple points I would like to talk on.

      You make a point suggesting the Stromer is fast, and has a high top speed. I agree with you here, but it’s not because of the motor – I just want that to be clear. It due to the the gearing. If you had a mid drive with the same gearing as the ST2-S, which is a 1×11 11-40T cassette and 52T chainring, you’ll most likely have a similar top speed beyond the street legal 32km/h or 20mph limit (assuming you’re from USA). That 52T chainring is the size of what road bikes use, so naturally you’ll have a faster bike. Which leads me into the point that Bosch motors have small chainrings and hence struggle with top speed, and supports your argument that it’s all about design – which I 100% agree on. And… it gets more complicated when you have mid drives like Bafang where you can customise your chain ring size.

      I guess this article was more focused on looking at the motors from a technical standpoint, and comparing them pound for pound, wattage for wattage. When you add things like the bike’s system and design, it becomes complex as you mentioned. Add the different country laws on electric bikes, and it becomes ridiculously complicated. But yes, I agree some companies can integrate a direct drive really well and provide outstanding performance like the Stromer. Everyone will have opinions on this topic and be loyal to their respective view. I’m planning on following up on this article, asking the same question but with a more thorough answer and better reasoning with all the knowledge I’ve gained through people’s responses, such as yourself. Be on the look out for that!

  6. Hey Eric
    Thanks for the information I (embarrassingly) should have known. It’s so refreshing to see seemingly simplistic things clearly, because someone has the gift to be able to explain them.
    I have owned many, many ebikes, and I couldn’t understand how the cheap ones with the same wattage as the Stromer could pale so in comparison.

    I am contemplating buying a Speciailized Turbo S, as they are discontinuing the line. The shops have discounted them considerably. The bike has had many design problems, but I’ve heard it is a very fast and Stromer-comperable bike. This model was the only one that challenged Stromer in terms of its design. Don’t get me wrong, I love my Stromer, but variety is nice. My back up bike is my Haibike, and its in the shop now. It was an amazing bike, when I first got it, but then I rode the Stromer. Love to hear your thoughts on the Specialized Turbo S. I know the new line is going mid-drive. The Bosch and Brose mid-drives will soon be the only “game in town”, with Stromer being the stand alone. Many complaints about the Brose motor not being powerful enough. I’ve test ridden the Brose and did not like it. The Optibike is another bike that perplexes me. Jim Turner is very much pro mid-drive, but his bikes have throttles. After reading your information, I’m guessing it’s all about his gearing. I had a throttle only bike and it was a terrible waste (but thankfully cheap)
    Again, I thank you for your enlightening information.
    I think a helpful e-bike article would be discussing the two paths of e-bike ownership: should you buy cheap and work your way up to premium, or buy top of the line? I worked my way up the chain. And although there are times when I’m ridding my Stromer, I wish I would have cut right to the top, I realize, I would have never appreciated without a thorough learning experience. Perhaps if I had a better understanding of gearing, I wouldn’t have had to navigate blind through which bike would work for me. When transitioning from manual bike to e-bike, even the entry-level models seem outrageously priced. But after ridding for a while, people understanding why the cost is justified. By the way, salesmen never clearly help you understand why the bikes work the way they do.
    Can’t wait to read your next article. I’m sure it will pave way to another learning experience.

    • No problem, I try to educate people so they understand what to get and/or what they’re getting.
      One reason that could explain why the Stromer was superior to the cheap ones is quality. The quality and grade of electronics the Stromer would’ve used would be much better, providing better efficiency and increased performance.

      Ah yes… The Turbo S. It was one of the first eBikes I saw and was like “Wow! That’s a beaut of an eBike. I NEED one”. It’s beautiful and the quality on it looks superb! I mean, what do you expect from Specialized right? I personally haven’t ridden one, so it’s hard for me to comment. I would love to ride one and review it. But yeah, it’s hard for me to say anything about it when I haven’t ridden one, or even seen on in real life. On paper, it looks amazing though. Shimano XT components, 48T chainring and 691Wh battery, the thing is built for a quality high speed commute. I say, if they’re on special and you can grab a deal, go for it! You can never have enough bikes haha! 😉

      The Optibike definitely looks like a interesting bike. It’s not my sort of bike. It seems to be mix of design, styles and components which I’m not really a fan of. I like well blended and integrated system and design, hence why I like the bikes from the big names with their never ending resources and teams.

      That’d be a good article and video to share with people. Thanks for that, I might explore that question after I release the second version of this article. Thanks for the comment and support Jan. Hopefully you got something out of this article and our discussion, and share it with others!

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