What powerful rear geared hub motor?

Hi all, I've been lurking around here a bit but this is my first post, go easy on this n00b please

Earlier this year I came across a cheap eBike conversion kit. I bought it and installed it on my old basic mountain bike that had been resting against the side of the house for a few years. Things have moved on a bit. I've long since sold that kit and bought several faulty electric bikes and scooters, fixed them up and sold them on

My current project is a budget (Mongoose) fat bike with a generic 250W 48V Chinese geared front hub motor. Had a ball riding it on a mucky and rough canal trail today, measured well over 1400W draw out of my battery up a short hill (59V fully charged 52V nominal 14S 12Ah battery - controller is max 30A), but the motor got very hot to the touch at the side of the axle where the cable is (no surprise). I like the power though, so I think I need to move on to my next project. I cycle mainly locally, could use the bike for an occasional 10km round trip commute. All is fairly flat here, no local significant hills or mountains. I could take the future bike on mountain trails (30 minute drive away) but this does not have my highest priority. That's probably why I am ruling out a mid drive. I'm in my early 50s, big lad (over 6'1 and over 100kg), but fairly fit for my age, although I don't see myself doing any down hill timed trials

So, my for my next bike (birthday present to myself) I'm going to be looking for a second hand mid level (USD1000, or so when new) hardtail or full suspension (that can be locked) 29er. And I want as powerful a rear wheel geared hub motor as possible. I'll worry about controller and battery later,

What would you recommend? I'm based in Ireland (in the EU), so stuff from the far east can attract hefty enough import taxes (23% of the shipped value + admin charge). The more power (without overheating the motor), the better

One stop shop for everything related to building a MAC geared motor bicycle
https://em3ev.com/shop/?prod_cat_=hub-motor-kits-motors
get your motor laced by them, into a good rim, and good spokes, get extra spokes

em3ev have been recommended to me before alright, they have an excellent reputation

Their most powerful geared hub motor is in the "Upgrade Mac Ebike Kit (~2,000W Max)" but there are no details at all about this motor. Can this motor handle 2kW continuous, say for a few minutes without any overheating / chance of burn out?

If I tick that motor, 10T winding (I presume 10T is best for torque, I don't need to go over 40km/h which both can do), 29" rim (what's the difference between DH21 CNC, DM24 CNC, DM24 Disc and DM35 Disc?), spokes, controller, cycle analyst, throttle, freewheel and torque arm, it comes to EUR629 including shipping. With customs charge this will be close to USD900. That's a lot of money...

Some of the various geared hubs, including the three most powerful I know of (mac, bmc, ezee, plus the gmac version of the mac) are listed on the http://ebikes.ca/simulator where you can model your system and situation / usage, and see when they overheat. Read the entire page first so you know what everythign is and how to use it, then setup systems like you might use, and play with them to see what they do.


Why do you require a geared hubmotor, rather than DD (direct drive) hubmotor?

The DD can handle more power for longer before overheating, for the same size motor, than a geared hub (though each has their advantages and disadvantages).

unkel said:

I want as powerful a rear wheel geared hub motor as possible

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I know one exists for electric motorcycles, because I've seen one. I've been unable to track down the manufacturer or a supplier. The only thing I know is that it has a rating of 3000W like many of its DD counterparts they are now putting on cheap electric motorcycle coming out of China.

amberwolf said:

Why do you require a geared hubmotor, rather than DD (direct drive) hubmotor?

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Because you can't pedal a bike with a direct drive motor. So not really an option if you want to cycle the bike yourself (or if you run out of battery!). I've had one before, great fun, but your bike is more of a motorbike with one, than it is a bike :lol:

I've only been made aware that cycling off the road (but in publicly owned and publicly accessible areas) like on mountain trails, or in forests, your bike has to be road legal in the EU. That throws a spanner in the works for me. I don't want to get into trouble, have my bike confiscated and / or lose my driving license(!). Maybe I shall stick with the motors that are officially just 250W and fit pedal assist and speed sensors (and get rid of the throttle)

unkel said:

amberwolf said:

Why do you require a geared hubmotor, rather than DD (direct drive) hubmotor?

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Because you can't pedal a bike with a direct drive motor.

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sure you can.

with power, it's exactly like doing it with a geared hubmotor.

without power, its not quite as easy as with a freewheeling geared hub, but it's easily possible.


even with my bad knees and joints and other problems, then once i can get it started moving, i can pedal my very heavy sb cruiser trike with two huge dd mtors on it, with no power at all, with the low gearing i have on it, although with my disabilities i am quickly exhausted and the pain of my joints will make me stop and rest frequently. it's not more than few mph at most, but a more normally-capable person would be able to pedal it faster with no power and higher gearing.

a regular bicycle with a dd motor i can pedal at more normal bike speeds, and i used to be able to do this easily for long periods, although with my present disabilities i am quickly exhausted and have to stop and rest a lot evne on a normal bicycle with no motor at all.

a more normally-capable person would easily be able to pedal an unpowered normal bicycle with dd hubmotor in a wheel.


so...while an unpowered dd hubmotor does have more resistance than a freewheeling geared hub, specificlaly more the faster you go, depending on the motor construction and system specifics, it doesn't stop the bike from being pedalled without power.

Thanks for all your help. I'm in the process of ordering a powerful Mac 12T geared hub motor from em3ev, laced into a 29" rear wheel for my 2015 Boardman Pro hardtail 29er. I'm taking the advice of em3ev to go with their 40A controller and I'm not going to go above a 52V battery

I also just bought a cheap old hand full suspension 26" wheeled 2008 Specialized Epic MTB (for just EUR150 / USD165) and I'm going to stick in a Bafang BBS02B mid drive motor. And see how they compare!

That should work, particularly since in a 12t winding, the motor will reach middle rpm where the motor stops running so inefficient a few seconds sooner than a fast winding would have. As the motor winds up to speed, it will stop trying to pull the full amps, effectively limiting excess motor heating. The slow winding should also help, since you won't be so conspicuously fast, despite lots of power when you need it. Nothing is under the radar when you cruise at 30-35 mph. You should be going much closer to legal speed with the slower winding.

The result, you should see, is that you really won't be able to pull 2000w max for very long at all, unless you are on crazy steep trail. On normal road, you should reach top speed rpm pretty quick, which will only require about half that 2000w. So you won't be pulling the full 2000w continuous much, unless you overload the bike with trailers, or just weigh 300 pounds yourself. Most of the time, you just can't make the motor draw much more than its butter zone wattage, 800-1000w, with the slow wind motors.

But if you overload,, till it can't go more than 5 mph up a long hill, that extra wattage will quickly melt your motor. That should be in the 400 pounds total weight ballpark. ( you, bike, battery, cargo) With a faster wind, the weight limit remains similar, but max continuous watts can increase, since top speed increases. Keep your total weight under 300 pounds, and no worries. Even on very steep hills that are less than a kilometer or so, the motor will heat up but never melt.

This sounds like giving it even more amps would be good, but its not, because of the amount of copper in the winding is not enough to handle really massive watts efficiently. That is why they suggest a 52v max. So a short burst of 3000w ( going to 72v or more amps) would not particularly be better, and would just waste too much of your battery into heating the motor.

Thanks for all the advice! In the meantime I stuck the BBS02B motor into the cheap old 26" Specialized full suspension bike I bought second hand for this project (with a cheap pack of four overstock 29.4V 6Ah kids scooter batteries, 2S2P for a 58.8V 12Ah setup). I have to say I've fallen for the mid drive setup. The torque is unreal in the lowest gear, you have to shift weight to the front to avoid a wheelie when you open the throttle from standstill. Had a pretty epic trip through a big storm here in Ireland yesterday over a rough and very mucky terrain and some flooded roads. I still got about 45km/h top speed, which is way more than I need

I guess I will have to choose my ideal setup now to work towards. It will have to have the BBSHD motor. With an aftermarket Lekkie very small chain ring for maximum torque. As for the form factor, definitely full suspension. Whether I should go 27.5", 29" or fat bike, I'm not sure yet. I only want to own one bike that should do everything for me. From doing the occasional 10km commute and local road trips to mucky fields and even some downhill / MTB trails. Thoughts?

Again, nothing will do everything. But your commute needs are very modest. That opens up some possibilities.

Maybe one bike, but two battery setups? You can still ride dirt with a lot of powerful battery, but run your very short commute on less power, meaning a nice small battery can get you there and back. Small enough to ride the rear rack with ease. Anything under 8 pounds is easily carried on a decent seatpost rack, if you stiffen your post with wood, like a broomstick that fits tight up the post.

Carry more battery for fast, fun rides after work, either with more in a backpack, or mount second battery on a handlebar box.

When I was running a higher power rear hub on dirt, I was carrying 52v 10 ah on the rack, and another 52v 10 ah on the bars. It worked good, but handled better when I put 5 ah up front. With that huge rear motor, I needed something up front anyway to balance it out.

Other options include two slim batteries on either side of the top tube. Like panniers, but between your knees.

I would not go fat for a one bike does it all setup, but do choose a good FS bike that can carry the wider, 2.4 or 2.5 wide tires with ease. If that ends up being a 29 er, fine. Stick to 26" if hub motor, but with a mid drive no real penalty for going big. Go with what can carry a wide tire, and with the best deal you can get.

Still think you should make a second bike just for the commute. Why? Because a combination dirt/ street tire will suck in the dirt. But if you take your wonderful dirt tires on street much, it will just wear them out in no time at all. Too soft. You need the second bike just so it can have a more durable tire. Not now, but eventually.

Cant ever have too many tools, but storing them can be a problem. My current stable, that I actually keep in good rubber, two motorcycles, one dirt one street. Two e bikes, one street on dirt. Three pedal only bikes, two street one dirt. That's not counting my wifes pedal bikes, 5 of them for various types of street, or easy dirt.

Its just much nicer to have the right tool for the particular type of ride. But to do this on the cheap, does take a lifetime of yard sales.

unkel...how are you enjoying your 12T MAC?

I went down the same path as you several years ago and started with a 12T MAC and eventually I came to the conclusion that a BBSHD is the way to go IF you are going to ride off road. Several reasons....it can be geared to operate efficiently at low speeds, it produces more torque after gearing than just about any motor around, it is relatively light, and with the motor in the middle of the bike the weight distribution and handling are as good as it can get.

A Direct Drive, a Geared Hub Motor, and a Mid-Drive all have advantages and disadvantages. IMO the best way to break them down is by how fast you want to go....A MAC works best in the 20-30 mph range, a Direct Drive works best at 30 mph and faster, and a mid drive works best from 0-20 mph. Those are NOT hard and fast numbers but just a general guideline.

A MAC will overheat if you push it hard at speeds below 20 mph or over 30 mph because it can only sustain about 1,000 watts continuously...see the Grin Tech page on the GMAC (same motor as the MAC just no freewheel).

No need for a mid drive IMO at speeds above 20 mph because a Geared Hub or a Direct Drive are a much simpler solution.

Above about 30 mph a Direct Drive would be the simplest and easiest.

Just a data point...I am running a 12T MAC in a 26" rim with a 26x3.5" tire that is 723mm OD, a 14s5p battery with HG2 cells, and a 12 FET Infineon controller set to 50A Battery and 140A Phase current. There are not many bikes around that will accelerate faster from 0-20 mph. BUT if I run a 29" wheel the 12T MAC is on the verge of over heating and it would be even worse with a faster winding like a 8T or a 10T. I can ride at about 27 mph all day when it is 95F but much faster and the motor temps climb too high...only way I can go faster is go to a larger diameter wheel/tire :wink: .

I am probably the #1 MAC fan but it does have its limitations and you do have to be aware of them and work with them.

Just FYI...EM3ev is no longer selling the MAC motor. If anybody has a good source for new MAC motors, please let me know. I have one ordered directly from MAC but after my first order, they have a minimum order quantity of "eight". I don't need eight motors :lol: .

unkel said:

Thanks for all the advice! In the meantime I stuck the BBS02B motor into the cheap old 26" Specialized full suspension bike I bought second hand for this project (with a cheap pack of four overstock 29.4V 6Ah kids scooter batteries, 2S2P for a 58.8V 12Ah setup). I have to say I've fallen for the mid drive setup. The torque is unreal in the lowest gear, you have to shift weight to the front to avoid a wheelie when you open the throttle from standstill. Had a pretty epic trip through a big storm here in Ireland yesterday over a rough and very mucky terrain and some flooded roads. I still got about 45km/h top speed, which is way more than I need

I guess I will have to choose my ideal setup now to work towards. It will have to have the BBSHD motor. With an aftermarket Lekkie very small chain ring for maximum torque. As for the form factor, definitely full suspension. Whether I should go 27.5", 29" or fat bike, I'm not sure yet. I only want to own one bike that should do everything for me. From doing the occasional 10km commute and local road trips to mucky fields and even some downhill / MTB trails. Thoughts?

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What I run with my BBSHD is a 28T Lekkie or a 30 T Mighty Mini (Luna) chain ring and a 22T White Industries "Green" 72 points of engagement freewheel and a Surly Singleator chain tensioner along with the widest rear tire I can fit in my frame but I am running a hardtail and I use the rear tire for some cushion/pseudo rear suspension. With a 14s battery, my top speed on flat ground is about 20 mph and I have plenty torque to climb hills. I really like the simplicity of the single speed but you could run a cassette or multi speed freewheel in the rear if you need to go faster than 20 mph. In the tight single track trails where I ride, I rarely get above about 17-18 mph. I took Mongoose Hitch fat tire bike and put a 29" SR Suntour Raidon fork (27.5" Raidon/XCR rubs on a 27.5x2.8" DHF) on it with a 27.5" bolt on wheel and a 27.5x2.8" Maxxis DHF and on the rear I run a 26x4.0" Maxxis FBR at 8.5 psi. A 4.8" FBR will fit in the Hitch frame if you want to go wider but the 4.8" tire slips on leaves pretty bad...it is too wide :wink: but it sure does give a cushy ride with 8 psi. No self steer with the 2.8" DHF and the suspension fork works great. Most other straight steerer forks will not allow you to use the 27.5x2.8" tire. I did not cut my steerer tube and added a Delta Cycle's Pro stem extender since I ride standing up 99% of the time due to lower back arthritis and a Diamondback suspension seat post for the 1% when I sit down. Crank Brothers Stamp 3 Danny MacCaskill pedals finish it off .

Since this thread is titled "geared hub" I did something very similar with a 12T MAC in a Mongoose Terrex frame but the MAC tends to overheat since I am constantly running it at full throttle which is 40A at very slow speeds. Liquid cooling solved the overheating but it has its own unique challenges :lol: . Somewhere on Endless Sphere I posted the specifics of both my ATF and water cooling experiments with a 12T MAC.

I mentioned it above but just a reminder...EM3ev no longer sells the MAC motor. You can purchase one directly from MAC but only once then the minimum order quantity is eight. Going to be interesting to see if anyone picks up the MAC sales that EM3ev dropped.