Understanding the Differences Between Direct Drive & Geared Electric Bike Hub Motors

Guest post by Alec Burney from E-Bike Kit.

“Which one is the best?” We get the question nearly every day, and it’s not the easiest one to answer… because ultimately it depends on your personal riding needs.

Do you want faster or lighter? More torque or quieter? More durable or less drag?

The first set of answers corresponds to direct drive motors: they’re faster, but have less torque, they’re more durable, but they’re also heavier and drag some, making pedaling less efficient, and their range on a full charge is a little less. Direct drive motors are nearly silent, humming along smoothly.

In contrast, geared motors make some whirring noises, but are light and small, they could almost pass for a normal bike hub, and there’s almost no drag when pedaling, but your top speed will be lower, and though they offer more torque, letting you climb hills quickly and accelerate from stop lights like nameless doped-up ex-racers, the nylon gears can wear out under hard use, and the gears make a bit of noise as they spin.

What nylon gears? Direct who? The reason you’ve got a choice at all is because there are two basic ways to get motor power from the hub to the wheel.

The Direct Drive Motor

The direct drive motor is the simplest: the outer shell of the hub is part of the motor, and has a big ring of strong rare earth magnets fixed to it.

When the motor runs, it drives the wheel directly. That’s where the name comes from. This means that the wheel is simply a motor with the shaft fixed in place so that the body of the motor (the outer hub shell, and this your wheel) spins instead of the shaft.

It’s a simple system, but the motor has to be big and heavy to produce enough power – a small motor spinning slowly doesn’t produce enough torque, and the speed you want your wheel to turn at is relatively slow, so the motor needs to be as big as possible to produce torque at low speeds, or…

The Geared Motor

The geared motor is a little more complex, but the clever complexity makes it lighter and smaller. You can see the gears in the photo.

Gears are awesome; you already have gearing on your bike – it can turn a bunch of low-torque circles into a few high-torque circles, or the reverse – this is handy if you’ve got a tiny motor and you want to make it push along a loaded bike.  The motor runs at high speed for efficiency and the gearing slows it down and increases the torque to push you forward.

And just like the gearing on your bike, ratcheting pawls let you coast without drag (in this case from the magnets), but the extra moving parts will eventually wear, just like the gears on a bike will some day crunch and skip and slip, and you’ll have to replace them (the nylon gears). And since the gearing is small and designed to make a wheel spin fast, heavier riders and riders with a lot of cargo may have trouble with long term durability.

For people that need a really strong push, special direct-drive hubs with the motors wound (using more copper) for higher torque and a lower top speed will make pulling heavier loads a breeze, they’ll go slower, but they’ll give lots of power and should last for many years.

The Answer

So the answer is: “it depends.”

If keeping your bike relatively lightweight is appealing and if stealthiness, freewheeling and increased range trump longevity, then a geared motor is likely your best option.

If you’re expecting to rely more heavily on the motor (and looking to haul more weight), craving a higher top speed (20+ mph), solid long-lasting value, and a quiet motor, then a direct-drive may be best for you.

Please keep in mind that these are generalizations and there are definitely some exceptions to the rule.

Also don’t forget that they’re similar in a lot of ways. They’re the same price (at least at E-BikeKit.com), they’re both easy to install, and you can run the throttle as much or as little as you want.  Whichever you choose, you’ll have a fantastic E-Bike, so don’t overthink it!

We’ve written about the advantages and drawbacks of each motor on our website, where you can compare the typical top speeds, ranges, and weights of the motors, in more depth.  We’ve gotten pretty good at helping people choose over the last five years.

Both are good motors, but to find the right one for you, you’ve got to ask yourself some questions. Of course, if you’re not sure, call and talk to someone or get to a great bike shop and ride a few.

Thank you to Alec Burney from E-Bike Kit for this article on the difference between direct drive and geared e-bike motors.

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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10 Comments

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  1. Rob June 6, 2013 at 4:29 am #

    DD is the way to go. Geared is just too slow and sounds weird.

    • Michael K. June 15, 2013 at 8:47 am #

      The ampedbike geared kits I sell can go 20+ mph and still freewheel. They have lots of torq to get up the hill around here. Not all geared motors are created equal.
      This is a great article.

  2. Lynn Ellsworth June 6, 2013 at 6:53 am #

    I like the idea of the geared motor. As the above article mentions an electric motor wants to spin much faster than our 24″ or 26″ bike wheel is able to spin so we are putting a large strain on a direct drive motor that is being forced to spin along with our wheel at a much slower speed than the motor really wants to spin.
    I have had 2 direct drive motors on converted bikes and they both worked fine but I rode a heavy cargo bike with a geared motor up a steep hill that would have bogged down either of my direct drive bikes.
    In fact I really want to try a geared motor mounted on the crank shaft instead of in a wheel hub. I just wish this could be done with belts instead of those damn obsolete chains and derailleurs.

    • Brad Sloan June 7, 2013 at 5:10 pm #

      I would think belts with Mid-Motor would be the way to go with an internal geared hub in the rear for pedaling. Low maintenance and no grease.

  3. Claas Borgers June 7, 2013 at 4:20 am #

    A 20″ wheel bike is a good choice for DD and delivers enough torque and RPM.

  4. Brad Sloan June 7, 2013 at 5:06 pm #

    I have used Direct Drive and Gear hubs bikes. Top speed is not that important. They all do 20mph which is the legal top speed. My Geared bike can go up to 25mph which is more than enough speed for a bike without suspension. It does make some noise, but not much and at top speed it is quite as a Direct Drive. It is quicker off the line than a Direct Drive and climbs hills better. In my opinion Geared hub are superior to Direct Drive hubs. I want to try out a Mid-Motor bike to see what it is like. I bet in the future, most ebikes with be Geared or Mid-Motor.

    • Patrick July 2, 2013 at 12:42 am #

      Can u give me more info about your motor?

  5. W W Ching June 7, 2013 at 5:59 pm #

    Not true that geared motor are slower, the motor could be wound to various speeds and gear ratio could also be designed for lower reduction. Our motor in the same hub comes in 200, 250, 300 and 350 rpm , 26″ wheel at 350 rpm is 28 mph , and that is with 36V and 37 mph in 48v

  6. Mickey McLaughlin June 8, 2013 at 5:35 am #

    This is a great way to get around Philly and any major city . Keep America going green .

  7. Savannah eBikes June 15, 2013 at 9:37 am #

    We prefer to use the geared motors on most of our conversions. The compact size, lightweight and immediate power feels better on the bikes then the weight and clumsy feel of a direct drive. Considering most of our customers use their bikes for 20 mile or less commutes a day to work, school and play, the life expectancy of the geared motor is definitely extended further than what others try to say.

    For heavier rider’s (+240lbs) and Trikes we tend to stick with the Direct Drive model for durability purposes only.

    Great article Pete

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