The Differences Between Direct Drive & Geared Electric Bike Hub Motors
Copyright: 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?
Copyright: 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?
he 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.
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.
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Image of a Direct drive motor
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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… |
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Image of a Geared motor
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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!
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.
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!
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.
