# Mid-Drive Integrated vs Mid-Drive Conversion vs Hub Motor



## PHeller (Dec 28, 2012)

I keep thinking my Big Fat Dummy (a long tail fat tire cargo bike) might compliment a ebike conversion nicely. It's not that bad to pedal with slicks and high pressures, but in order to get the benefit of fat tires, I've got lower pressures, and when I do that, every mile is a workout (for better or worse). Throw a few kids on it and we're really working. 

I've been talking with a friendly frame builder about some Mad Scientist-Level stuff, and along with some modification of my frame for better standover and possible travel couplers, another thought we had was to add a mounting plate for a Mid-Drive Motor like a Shimano Steps. 

Then I got to thinking more about this idea, and I came to some conclusions:

Added Cost - The mounting plate, fabrication, and potential motor cost would likely add up very quickly. Best estimates are around $1600 without battery. I would likely never get that back out of the bike. 

No Going Back - The integrated mid-drive would also lock me into ebike life for the rest of my time with the bike. No going back to analog. 

Integrated Mid-Drive vs Conversion Mid-Drive:

That last point - being able to swap back to a normal riding experience, would also remove the Mid-Drive Conversion as well. While I could remove the motor, it wouldn't be an "on the fly" type of conversion. 

Mid-Drive Conversion vs Hub-Motor:

The more I think about it, the more it seems like a hub motor would be the best option for me. I don't need high-tech pedal assist. I really just want something to act as more of a car replacement - quickly get from Point A to B. 

Some other advantages could be the ability to get a smaller rear wheel for a lower deck height (although BB height could be an issue).

*What are the disadvantages of Hub-Motors? Less power? Less efficient? More prone to failure?*

It seems like plenty of big name ebike manufacturers are still rolling out new models with hub motors. Some brands even utilize hub motors in electric motorscooterthings, so they can't be weak.


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## Varaxis (Mar 16, 2010)

PHeller said:


> *What are the disadvantages of Hub-Motors? Less power? Less efficient? More prone to failure?*


Yes, yes, and yes.

Generally, to get a hub motor to feel comparable to a mid-drive, you need at least double the wattage rating on the hub motor. I honestly doubt a 750W hub motor will even match a 250W Shimano STEPS (the Shimano is known to max out at 450W or so). That ties in with the hub motor's lower efficiency--with a 500Wh battery, you'd only be able to go 1 hour on a motor pulling 500W of current.

The wheels containing hub motors also "self-destruct", with spokes constantly coming loose and breaking. The motors also have a tendency to burn out when you ask too much out of it (going uphill, starting from a stop while carrying a heavy load, etc.). The more under-powered the hub motor, the more likely it'll end up burning out; the more powerful, the more likely the wheel will fail.

Mid-drives just have better torque availability at all speeds. The hub motor will feel bogged down at low speeds and its top-out speed will feel extra limiting, since it feels like its power band is so small. Mid-drives take advantage of the drivetrain's gears, vastly expanding the speed ranges that the electric motor will be good at. Hub motors also need more wiring due to needing a separate controller. Mid-drive also keeps weight centered. Mid-drives retain more of a bicycle riding experience, especially if they have sophisticated torque sensing. I'm honestly not fond of the "motor vehicle" experience, especially when the vehicle is so low power, but bicycling with a little extra power feels thrilling.

By the time you consider the cost of extra wheel and what not, a mid-drive add-on doesn't seem too bad. Wheel quality is relatively important. I wouldn't want to ride a cheap wheel, especially one that affects my tire choice. I'm spoiled by tubeless's air retention reliability.

Downsides of mid-drive: more strain on drivetrain, especially if you mash or push the bike's limits, trying to pedal in a way you normally couldn't without a motor. Examples include starting in too high of a gear when accelerating from a stop, mashing up a steep hill with little momentum, and/or slogging through deep draggy sand. It's common to see accelerated wear on high gear/cogs on first-timers' ebikes.

Those electric motor scooters feel underwhelming to me. Primitive tech... in general, electric motors are happiest when they're spinning fast, and these hub motors have a single gear reduction in place to tune it to the RPM of a typical bicycle wheel moving at a certain speed (15 MPH maybe). These hub motors will be their most efficient when the wheel is traveling at near its top speed.


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## PHeller (Dec 28, 2012)

Hmmm...convincing. 

I just wish the mid-drives didn't hang off the front of the BB. If I could tuck it inside the triangle I'd be all about it.


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## TeeCee (Jan 7, 2021)

My BFD sports a Bafang mid drive, and it works superbly. No regrets, and and I can remove it back to the original if necessary.
I couldn't understand why Surly offered the BD in a electrical model (Big Ezey) but not the Fat version. Much more sense on the fat.
I use it mainly off road on 4.8 tires, but have 3" 2 9ers too.


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## fos'l (May 27, 2009)

Hub motors are an excellent choice for some conversions with the most significant liabilities being steep ascents (resolve with a big enough motor) and flat tires (resolve with appropriate tires). Additionally, some users have 25,000+ miles on direct drive motors since they have basically one moving part. Peruse endless sphere and look at the tutorials on ebikesca for more information.


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## matt4x4 (Dec 21, 2013)

Depends, you talking hub motors but what kind?

Geared are lighter, easier to break but the over all gearing of the sun gears and the planetary gears and the final gear reduction can be quite good for climbing hills but leaves you with no regen, the gmac geared can lock and give you regen. Direct drivers are bigger and heavier but are super strong as there are no moving parts unlike the geared hub motor. The only things I have even actually done to the many direct drive motors I've owned is replace one cover plate bearing, replace hall sensors, replace phase wires right from the motors windings out the axle. The whole system is pretty well streamlined, theres not much action going on other then a few select companies innovating the hub motor market, obvious companies. 

The smaller geared motors you can't push them much beyond their true rating. The MAC is about the best you will get for highest power on a geared motor, MAC is mass produced, you might be able to find something somewhere that can handle more, but you can buy parts and most importantly gears from MAC.

You could tuck your mid drive onto the top of the bottom bracket.
You could route the chain directly to the rear wheel instead of going through the drive train.
I do not like the rc motor mid drives, the sound is to much.


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