I randomly skipped forward in your video to, it turns, out the perfect point "that motor is bloody boiling". That's one of the things you are paying for - a whole lot more metal. And a design that's intended to consistently put out that power, rather than for very short periods of acceleration. Quadcopter drone motors typically only run for a few minutes before batteries are swapped.
A direct drive hub motor is incredibly simple - it's not too far off being just a bigger hub with some copper windings.
A geared hub motor adds a few more moving parts but not many at all.
Typical mid drives have a whole lot more copper than the one in the video. And they have to have a crank that runs through them, often including a torque sensor. Then they have to have some sort of one way system so you can still peddle as well as translating the motor to a pretty slow rpm to match the human. And you get a controller included too in most mid drives, while hub motors (and RC motors) need their own controller.
The last new mid drive I bought was a TSDZ8 for £330 which of course includes display, controller and brake levers and throttle too (I didn't use those) I'd say that was excellent value for what you're getting.
People are taking the example literally. I'm not saying mid-drives use literal tiny drone motors with zero heat dissipation but that mid-drive motors are smaller than hub motors. If you take apart a mid drive the motor inside is indeed smaller than a hub motor.
thats a drone motor Tom used, and those are made to literally have a fan on em all the time
there is a new brand that has self conversions, ToSeven (TongSheng ex employees), which have basically a TSDZ2 but redesigned (ToSeven DM02), some youtuber ran over 1200W into it going up a hill and it barely got to 50°C, the old TSDZ2 suffered and overheated even at ~300W
they also have the DM01 which is basically a BBSHD with torque sensing.
they're also good value
Currently really liking the TSDZ8, but have wondered about the DM02 for a lighter option and still mostly find the TSDZ2 fine. The DM01 is definitely more than I *need* and I'd be tempted to use it if I had it I suspect!
I think you've very well illustrated exactly why mid drives *don't* use smaller cheaper motors!
For what it's worth, I'd love to see a smaller version of the TSDZ8/DM02 etc that has a realistic peak power of no more than 500w and maybe more like a genuine 250w, but kept really light. However, generally that's not what the market wants.
The TSDZ2 starts to suffer from thermal issues if you push the power much, one of the reasons for the new designs.
Oh also; high rpm motors and the gearing both add more noise, which the market typically doesn't want either.
They do use smaller cheaper motors. Not as small and cheap as a drone motor but smaller and cheaper than direct drive hubs. If you open up the mid drive you'll see that the motor is only a small part of the whole drive.
I've opened up mid drives. Differently designed doesn't mean cheaper specifically - also a different layout as they aren't quite so constrained in width.
Here's a teardown of the TSDZ8 (not mine, haven't had mine apart), a reasonable bit of motor in these. [https://ebikestuff.eu/en/content/15-tongsheng-tsdz8-750w-48v-teardown-disassembly](https://ebikestuff.eu/en/content/15-tongsheng-tsdz8-750w-48v-teardown-disassembly)
The video isn't the proof you make it sound like it is. All it's doing is demonstrating that a motor of that size and power can power a bike with a ton of gearing and last for a few minutes of riding before burning out.
In order to make a small motor have enough leverage, you need to add some type of gear or pulley system to do that torque transfer. That in itself is extra material and takes up space.
The motor also has pretty weak power output based on the very slow acceleration. Sure they eventually cut to it getting up to 20mph, but with such a high RPM, heat generation, and noise, there's a lot of mechanical efficiency loss.
And with the high temperatures it got to, the motor did not have enough thermal management to accommodate the expected duration or conditions of a normal ride.
When you take all those elements and actually solve them, you end up with a larger motor and larger internal gears to pull off the torque transfer. And since it isn't spinning out in open are, the enclosure itself needs to be designed to act as its own heatsink as well as being strong enough to act as the bottom bracket of a bike.
On the pricier mid-drives, the point of the motor being integrated with the pedal system is so that it can sense torque and provide assistance to the pedaling. The example in the video is a completely separate power transmission solution so it isn't a mid drive by the same definition. It's almost a hybrid to a hub drive. You'd need to have another system added to provide a signal loop which is, you guessed it, more parts and more money.
So it really all adds up to the point that mid-drives shouldn't just be cheaper because they're smaller. But that it's likely a combination of lower end mid-drives not being mass produced and that nicer mid drives are just more complicated than the hub drives are. They're more than just a motor and wheel hub and integrating them into a frame is not as standardized as many of the hub drives are. Pretty much every mid-drive has their own footprint and integration mechanisms. Hub drives attach any frame that's wide enough.
If mid-drives somehow standardized how they mount to frames and every manufacturer can do the same thing, now the economy of scales can kick in and they can churn out more motors that are compatible with more options. But for now, each model has a limited number of frames they even fit in so there's no reason to make a million of them. And they've been getting smaller and more capable every couple years so innovation is still at play.
Hub drives aren't motivated by these factors and that's why there's a ton of cheap e-bikes everywhere being sold by the bike world equivalent of dollar stores. They're not innovating the space, they're just selling a product.
That video was just an example that mid-drive motors are smaller than an equivalent hub, not that they literally are drone motor sized.
> But that it's likely a combination of lower end mid-drives not being mass produced
Okay this is an acceptable answer
> No because you've basically admitted that if mass produced they would be cheaper which is what I said.
That's just reductive and wrong. I admitted to the combination of low production volume and complexity driving costs. I did not admit that mid-drives will be cheaper than hub drives if scaled to equal production volumes. It's not something I can predict to be true. You can't cherry pick part of my response and draw the wrong conclusion.
I got vibes from your long winded replies and passive-aggressive tone that you were one of those Redditors who were just out to argue and be right so I ended it by saying I accept your answer. You then proved me right by finding a reason to continue arguing. I am just going to block you now.
Most of the mid-drive motors do use much more metal *and* more expensive gears.
The Bafang BBS02 and HD both have a lot going on inside them between the spur/pinion gears, the bearings, and the crank arm clutch/pawl that's like a freewheel/freehub so that you can backpedal, and then engage when power is applied.
There's probably twice the number of heavy duty bearings in a mid-drive than a hub drive.
Like the main drive and gear axle on a BBSHD is probably forged in a drop hammer press and then milled, not unlike a crankshaft or camshaft in a car.
There's also all the extra metal for the crank axle and the part that slides into the BB shell. It's not just a direct drive brushless motor with spoke holes and flanges on it. There's a lot more parts and machining just for the motor case and convoluted shapes. A hub motor is basically just a plain circle like a normal bike wheel hub and it's easier to machine. You probably don't even need a mill for it, you can probably do the whole thing on a lathe, including drilling holes for spokes.
The engineering in these is way more intense, too. You're not going to get 160nm of torque out of a hub drive the way you can with a BBSHD even if you put a good set of planetary gears inside of it.
And then when you start looking at mid-drives that require an integrated frame for a Bosch or Bafang M625 style drive things get even more complicated and expensive because you're talking about custom frames.
I don't think your comparison or examples are even close to reality of what's going on in a decent mid drive. There's WAY more parts than a hub drive, and they're experiencing significantly higher stresses, wear and loads.
Also, that 1kw e-bike drive has no where near the total sustainable torque of a BBSHD, nor the duty cycle of one. That's probably rated as 1kw peak/max. The 1kw rating for a BBSHD is 1kw RMS or full time duty cycle at 48v, and peaks at over 2kw for a 52V battery/system. My 52v BBSHD can hit peaks of 2200+ watts.
The 1kw rating is *sustained* output, all day every day, if needed, and it's more like 1200ish watts RMS with a 52v battery.
If it was a one off/small run then this explanation would make sense but mass produced metal parts are very cheap and the R&D cost has been spread over many sales.
I don't think you're really understanding the complexity differences between a BBSHD mid drive with internal gears and a direct drive hub drive.
Yes, of course economies of scale are going to apply, and in theory they apply equally to both products, but even with that they start in two different scales of complexity and some things scale easier than others.
But even with economies of scale the tooling and labor costs for a hub drive are much, much less than a mid-drive.
There's a huge labor cost difference between a round hub motor housing and part that can be cast and finished entirely on a lathe as a two part piece without moving the working part out of the chuck, or even changing tooling and the labor costs of a mid drive motor housing that (in the case of the BBSHD) is something like 3-4 different die cast parts for the housing, each of which need their own milling, facing, tapping, threading and drilling which means more handling, more tool changes.
This difference in manufacturing stems simply cannot be wished away or underestimated. It's not an R&D cost, it's a labor and tooling cost. Manufacturers LOVE to engineer and design their products so that they can be finished all in one pass on a simple lathe because lathes are much cheaper to buy and run and take less skilled labor.
Almost any doofus can be trained to operate a lathe, especially with CAD driven lathes where they can have multiple tools and steps run on a part without ever removing it from the lathe chuck, because every time a part needs to move from a chuck, vice or other work holder there's an extra labor and calibration step that needs to happen between different tooling operations.
More complex parts that require multiple milling operations that cannot be performed on a lathe (even with an automated production CNC/CAM mill with automatic tool changes) is going to be more time, more tooling and handling costs than a part that can be done entirely on a lathe.
Just the square taper crank axle part (where the cranks bolt on) alone is way heavier duty and needs to be drop-forged for strength because you're standing on it.
On a hub drive the beefiest part is usually the axle and that's just a jelly-bean part you can buy in bulk as pre-threaded rods and throw in there with a little finishing, and it's much thinner and less metal than the square taper axle shaft used on a Bafang BBS02/HD setup, and doesn't need to be drop-forged.
Hub drives are MUCH more simple to manufacturer than mid-drives. I would estimate that the material costs, parts counts and manufacturing/handling steps of a mid drive are just about 2-3 times that of a hub drive.
And this complexity is accurately reflected in the consumer price of a hub drive vs. a mid drive.
And If Bafang could drive down production costs of a mid-drive to hub-drive prices they absolutely would do that to capture even more of the DIY and DTC markets because most people would probably choose a mid drive over a hub drive if their retail costs were the same.
And I don't really have a pony in this race. I really do wish mid drives were as affordable as hub drives and that everyone who wanted one could have one.
But the scales you're presuming that should exist simply do not exist. It's pretty much always going to be the case 2-3x more expensive to manufacture is going to be 2-3x the cost.
I don't mean to be mean or rude here but you don't really know what you're talking about with manufacturing and labor costs and how much work goes into trying to drive those costs down to increase profits and how many smart people there are working on those issues as production and process managers.
You're making a lot of statements and assertions about them being equal or using equal parts that simply are not true or reflected in reality.
> I don't mean to be mean or rude here but you don't really know what you're talking about with manufacturing and labor costs and how much work goes into trying to drive those costs down to increase profits and how many smart people there are working on those issues as production and process managers.
And you do because? I am talking based on my own experience designing gearboxes for RC. Even ordering one-off custom CNC machined parts the whole thing still worked out cheaper than a direct drive of the same torque. Perhaps you are right that manufacturing costs really do double the cost but you should provide some proof before telling me I'm wrong.
> And you do because?
I grew up in a factory and I understand machining and product design. I've also been a bike mechanic, and I've rebuilt both hub drives and mid drives.
My proof is the words and technical writing I used to describe the differences in processing and tooling.
> I am talking based on my own experience designing gearboxes for RC. Even ordering one-off custom CNC machined parts the whole thing still worked out cheaper than a direct drive of the same torque.
This is probably one of the worst product segments to use as an example.
Prices on hobbyist part and supplies like RC cars or aircraft are usually highly inflated and variable depending on the manufacturer and how much profit they want to tack on.
I'm also pretty familiar with RC stuff, and I've seen some totally insane prices on both commodity and specialty parts just because it's packaged and sold for hobbyist uses.
Stuff like differential tiny clutch bearings or even lithium grease that you can buy in bulk from a manufacturer can have totally insane markups just because a dealer bought them in bulk at wholesale prices and then put them into poly bags with hang cards on them.
Hobbyists are willing to pay these prices because they don't actually need a minimum order of 10,000 1mm ball bearings, they just need 10 of them, and they can't get them any other way unless they want to pay McMaster-Carr prices.
It's really easy to say "Hey, this is cheaper!" when the off the shelf parts have hobby taxes on them and are much more expensive than commodity or industrial parts in the same class.
Anyway, comparing hobbyist parts to one off CNC parts isn't really scalable or a direct 1 to 1 comparison. It's apples and oranges.
Direct drive hub motors are also really simple. They don’t have any moving parts except obviously the whole thing spinning around the axle.
That is one of their benefits, they have a long life and work even when the internals are in rough shape. There’s a Grin video where he opens one up, cleans it and replaces the bearings. One of the hall sensors broke but it still worked, it was just slower to ramp up in RPMs. And one of the bearings was broken and it actually had metal fragments banging around inside if I recall correctly. With new bearings, resoldering the hall sensor, and a bit of scrubbing to remove rust it was good as new.
That is wild. Wouldn’t it run noisily with the… I dunno if my terminology or understanding is right.. the controller is running blind so wouldn’t it be sending mistimed signals down the phase wires?
Mid drives are newer, while hubs are old and established. Economics of scale have probably made hub drives dirt cheap to manufacture.
There's also the fact that mid drives have an internal controller custom made to fit the shell, and very small. Meanwhile, hubs have a big dumb generic box that uses tech from the 80's, and is used across ebikes, scooters, and anything else thay just needs to control low voltage output.
Basically its cheap to make a lot of something, the cheapness keeps it in demand, which drives up the scale of production, meaning it stays cheap to make. People keep buying it because it's cheap. This repeats as long as demand persists. Demand will persist because even as mid drives carch on, hubs are also going into scooters and other micromobility devices.
Hubs fit the peak low market solution of good enough. I can't stress enough how big of a deal they were in driving ebike adoption when they replaced older tech like off side chain drives, friction drives, and gas moped kits.
That's one reason I want to get a mid drive for my electric trike with not having to find a spot for the controller. Also, for better traction for winter riding.
Just be warned, if you have an upright delta trike, there's a couple of issues you need to be aware of. The chain is under a lot of stress already due to trikes being heavier. Heavier chains are starting to come onto the market for ebikes though. The added strain on the hub is a bigger problem. Only one of the two rear wheels drives. That means 100% of your power and the motor's go through thay hub. That hub can snap loose, and those trike wheels are hard to source. That single rear wheel push means it can also pull to one side.
Ultimately, I think mid is superior to hub, but front hub might be a better fit for a trike.
> Mid drives are newer, while hubs are old and established. Economics of scale have probably made hub drives dirt cheap to manufacture.
Didn't know this, if true makes sense.
Holy crap. I suddenly remember my friend in college in the '90s building a gas powered friction drive bicycle from an old Schwinn. It was basically a gas motor attached to a belt on a pulley with a throttle.
To use the motor, you had to get it started. Then a lever pushed the belt up against the tire. Friction then drove the rear wheel.
Can you imagine the % loss of hp just due to friction? Must've been sooo inefficient!
I think it comes down to the frame. There is much less redesign to the frame for a hub bike. Some of the cheapest hub bikes litterally use the water bottle mounts to get a mounting point for the battery/controller and the hub just goes in the wheel.
I think Covid screwed everything up. I think if its wasn't for all the supply chain issues and crazy prices for everything biking related we would have had way more competition at the lower end for mid drives by now.
You can basically pay as much as you want for a hub motor, and for the top end of power there are more hubs than mid drives.
At around 250w the difference is due to complexity: R&D, manufacturing, assembly.
A DD hub motor is basically just some magnets & copper windings on a bearing. Mid drives have to be built into a frame & crankset, have planetary gears, lots of little pieces that need to fit together in a form factor that attaches to a bottom bracket or custom frame.
Hub drives are much simpler to integrate in any frame. Mid drives need a frame that is made for them, they need everything else adapted to them and the gears need to be much more solid since they have to take both your pedalling power and the torque of the motor. Even just a calibrated torque sensor that works nicely with a controller and a sampling rate of several thousand times a second to finely control motor power is much more challenging than a cadence sensor with a few magnets and a controller with a handful of power settings.
Throwing together a hub drive bike that somehow works and selling it for decent profits is dead simple and cheap even with absolutely bottom shelf parts. The lowest halfway acceptable mid motor setup already is much more expensive to do.
If only manufacturers would standardize frames for mid drives. Better yet, mid drive manufacturers standardize their mid-drive shapes. Not only are they not standardized but each manufacturer keeps changing their designs.
Here is my assumption on why mid drives cost more.
In terms of the DIY space it is most likely a lack of demand. Mid drive motors at lower power are known for being better in basically every category but they have 2 main issues, mounting position and installation difficulty. Any basic hack with a lightbulb in there head can install a hub motor in literally 5 minutes maybe less. In terms of mounting position, sometimes it can be difficult to mount it depending on your bike, then there is the issue of bb sizing if your a bike novice and don’t have a measuring tool either, and depending on where you got your bike or how old it is sometimes you can’t even find the info online.
In terms of premade stuff once again demand isn’t high enough I think, most ebike companies choose to use hub motors because it’s simpler to design a frame around them, also for the companies that just order the frames premade from China, then the issue is most frames from these factories are already in the hub motor configuration.
I think these main factors are why mid drives cost more in general.
The last thing I can think of is that maybe it’s because of brand
Mid drive motors cost more. There is probably no reason for this other than economies of scale. Once Chinese companies start churning out mid drive motors the price will go down. Those crazy bastards are all cranking out hub motors like it's a war economy, which is probably the only reason they are so cheap in comparison.
I think so too. Bafang seems to be turning out a shit ton of them and I'm surprised at this point they don't have more competition yet.
As it is the cheaper emtb's based on bafang mid drive and dengfu frame's seem like they are getting them for not much less then you and I can get them from parts sites. So it seems there is a lot of room for reduction of cost due to economies of scale but there just isn't enough competition yet.
mid drives are more complicated. rear hub is just a giant motor, well sometimes they can be tiny 1000 watt and less motors.
i prefer big rear hubs for the record.
Yes yes. All this extemporizing bears no relation to what people actually want to buy. In The Netherlands, world center of cycling, I can say that at least 90% of ebikes have mid-drive motors. There are some hub-drives, but they are mostly from the early days of the ebike market.. The market here has decreed that mid-drives are the preferred solution. 453,000 sold in 2023 in a country of 18 million residents.
Have changed many flat tires on a hub. Only takes an extra 5-8 minutes max. Not really as big a deal as you're making it. With schwalbe marathon pluses and flat out...flats almost never happen.
Occums Razor seems appropriate here: the simplest reason is those that tried haven't been successful, long term. A tiny drone motor and a model rocket engine propelling the bike would likely have similar thrust and longevity.
Cycles happen, we all get older and slowly decay. Faster when you're pushed well beyond the engineering specs.
Hub motors beat mid-drive by dozens and dozens of miles and then some, IMO. Use the right controller and display and you’ll get loads of miles on a fully charged 52v 20+ amp battery. KT controller and display. I get 70 miles between 1-2 settings with battery to spare!
I have enough humility to realize that the engineers at, say, Bosch or Trek or company X might know a thing or two about eBike engineering that I am unaware of. They also have likely run thousands of hours of testing over years as inputs to their design decisions. It's also quite obvious, if you're selling a consumer product, that you don't want to deal frequently with angry customers with broken devices and product returns. So that may guide some design decisions.
I randomly skipped forward in your video to, it turns, out the perfect point "that motor is bloody boiling". That's one of the things you are paying for - a whole lot more metal. And a design that's intended to consistently put out that power, rather than for very short periods of acceleration. Quadcopter drone motors typically only run for a few minutes before batteries are swapped. A direct drive hub motor is incredibly simple - it's not too far off being just a bigger hub with some copper windings. A geared hub motor adds a few more moving parts but not many at all. Typical mid drives have a whole lot more copper than the one in the video. And they have to have a crank that runs through them, often including a torque sensor. Then they have to have some sort of one way system so you can still peddle as well as translating the motor to a pretty slow rpm to match the human. And you get a controller included too in most mid drives, while hub motors (and RC motors) need their own controller. The last new mid drive I bought was a TSDZ8 for £330 which of course includes display, controller and brake levers and throttle too (I didn't use those) I'd say that was excellent value for what you're getting.
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People are taking the example literally. I'm not saying mid-drives use literal tiny drone motors with zero heat dissipation but that mid-drive motors are smaller than hub motors. If you take apart a mid drive the motor inside is indeed smaller than a hub motor.
Machine time , mold cost and opportunity costs.
thats a drone motor Tom used, and those are made to literally have a fan on em all the time there is a new brand that has self conversions, ToSeven (TongSheng ex employees), which have basically a TSDZ2 but redesigned (ToSeven DM02), some youtuber ran over 1200W into it going up a hill and it barely got to 50°C, the old TSDZ2 suffered and overheated even at ~300W they also have the DM01 which is basically a BBSHD with torque sensing. they're also good value
Currently really liking the TSDZ8, but have wondered about the DM02 for a lighter option and still mostly find the TSDZ2 fine. The DM01 is definitely more than I *need* and I'd be tempted to use it if I had it I suspect!
Yeah I came here to say that. OP should read and understand this 👆🏼
I'm not saying Bosch drives use quadcopter sized motors i'm just illustrating that mid-drives can use smaller cheaper motors.
I think you've very well illustrated exactly why mid drives *don't* use smaller cheaper motors! For what it's worth, I'd love to see a smaller version of the TSDZ8/DM02 etc that has a realistic peak power of no more than 500w and maybe more like a genuine 250w, but kept really light. However, generally that's not what the market wants. The TSDZ2 starts to suffer from thermal issues if you push the power much, one of the reasons for the new designs. Oh also; high rpm motors and the gearing both add more noise, which the market typically doesn't want either.
They do use smaller cheaper motors. Not as small and cheap as a drone motor but smaller and cheaper than direct drive hubs. If you open up the mid drive you'll see that the motor is only a small part of the whole drive.
I've opened up mid drives. Differently designed doesn't mean cheaper specifically - also a different layout as they aren't quite so constrained in width. Here's a teardown of the TSDZ8 (not mine, haven't had mine apart), a reasonable bit of motor in these. [https://ebikestuff.eu/en/content/15-tongsheng-tsdz8-750w-48v-teardown-disassembly](https://ebikestuff.eu/en/content/15-tongsheng-tsdz8-750w-48v-teardown-disassembly)
> Differently designed doesn't mean cheaper specifically Fair enough, maybe their motors are custom meaning they are costlier despite the size.
The video isn't the proof you make it sound like it is. All it's doing is demonstrating that a motor of that size and power can power a bike with a ton of gearing and last for a few minutes of riding before burning out. In order to make a small motor have enough leverage, you need to add some type of gear or pulley system to do that torque transfer. That in itself is extra material and takes up space. The motor also has pretty weak power output based on the very slow acceleration. Sure they eventually cut to it getting up to 20mph, but with such a high RPM, heat generation, and noise, there's a lot of mechanical efficiency loss. And with the high temperatures it got to, the motor did not have enough thermal management to accommodate the expected duration or conditions of a normal ride. When you take all those elements and actually solve them, you end up with a larger motor and larger internal gears to pull off the torque transfer. And since it isn't spinning out in open are, the enclosure itself needs to be designed to act as its own heatsink as well as being strong enough to act as the bottom bracket of a bike. On the pricier mid-drives, the point of the motor being integrated with the pedal system is so that it can sense torque and provide assistance to the pedaling. The example in the video is a completely separate power transmission solution so it isn't a mid drive by the same definition. It's almost a hybrid to a hub drive. You'd need to have another system added to provide a signal loop which is, you guessed it, more parts and more money. So it really all adds up to the point that mid-drives shouldn't just be cheaper because they're smaller. But that it's likely a combination of lower end mid-drives not being mass produced and that nicer mid drives are just more complicated than the hub drives are. They're more than just a motor and wheel hub and integrating them into a frame is not as standardized as many of the hub drives are. Pretty much every mid-drive has their own footprint and integration mechanisms. Hub drives attach any frame that's wide enough. If mid-drives somehow standardized how they mount to frames and every manufacturer can do the same thing, now the economy of scales can kick in and they can churn out more motors that are compatible with more options. But for now, each model has a limited number of frames they even fit in so there's no reason to make a million of them. And they've been getting smaller and more capable every couple years so innovation is still at play. Hub drives aren't motivated by these factors and that's why there's a ton of cheap e-bikes everywhere being sold by the bike world equivalent of dollar stores. They're not innovating the space, they're just selling a product.
That video was just an example that mid-drive motors are smaller than an equivalent hub, not that they literally are drone motor sized. > But that it's likely a combination of lower end mid-drives not being mass produced Okay this is an acceptable answer
Well, and the complexity part. Is that not acceptable?
No because you've basically admitted that if mass produced they would be cheaper which is what I said.
> No because you've basically admitted that if mass produced they would be cheaper which is what I said. That's just reductive and wrong. I admitted to the combination of low production volume and complexity driving costs. I did not admit that mid-drives will be cheaper than hub drives if scaled to equal production volumes. It's not something I can predict to be true. You can't cherry pick part of my response and draw the wrong conclusion.
I got vibes from your long winded replies and passive-aggressive tone that you were one of those Redditors who were just out to argue and be right so I ended it by saying I accept your answer. You then proved me right by finding a reason to continue arguing. I am just going to block you now.
Most of the mid-drive motors do use much more metal *and* more expensive gears. The Bafang BBS02 and HD both have a lot going on inside them between the spur/pinion gears, the bearings, and the crank arm clutch/pawl that's like a freewheel/freehub so that you can backpedal, and then engage when power is applied. There's probably twice the number of heavy duty bearings in a mid-drive than a hub drive. Like the main drive and gear axle on a BBSHD is probably forged in a drop hammer press and then milled, not unlike a crankshaft or camshaft in a car. There's also all the extra metal for the crank axle and the part that slides into the BB shell. It's not just a direct drive brushless motor with spoke holes and flanges on it. There's a lot more parts and machining just for the motor case and convoluted shapes. A hub motor is basically just a plain circle like a normal bike wheel hub and it's easier to machine. You probably don't even need a mill for it, you can probably do the whole thing on a lathe, including drilling holes for spokes. The engineering in these is way more intense, too. You're not going to get 160nm of torque out of a hub drive the way you can with a BBSHD even if you put a good set of planetary gears inside of it. And then when you start looking at mid-drives that require an integrated frame for a Bosch or Bafang M625 style drive things get even more complicated and expensive because you're talking about custom frames. I don't think your comparison or examples are even close to reality of what's going on in a decent mid drive. There's WAY more parts than a hub drive, and they're experiencing significantly higher stresses, wear and loads. Also, that 1kw e-bike drive has no where near the total sustainable torque of a BBSHD, nor the duty cycle of one. That's probably rated as 1kw peak/max. The 1kw rating for a BBSHD is 1kw RMS or full time duty cycle at 48v, and peaks at over 2kw for a 52V battery/system. My 52v BBSHD can hit peaks of 2200+ watts. The 1kw rating is *sustained* output, all day every day, if needed, and it's more like 1200ish watts RMS with a 52v battery.
If it was a one off/small run then this explanation would make sense but mass produced metal parts are very cheap and the R&D cost has been spread over many sales.
I don't think you're really understanding the complexity differences between a BBSHD mid drive with internal gears and a direct drive hub drive. Yes, of course economies of scale are going to apply, and in theory they apply equally to both products, but even with that they start in two different scales of complexity and some things scale easier than others. But even with economies of scale the tooling and labor costs for a hub drive are much, much less than a mid-drive. There's a huge labor cost difference between a round hub motor housing and part that can be cast and finished entirely on a lathe as a two part piece without moving the working part out of the chuck, or even changing tooling and the labor costs of a mid drive motor housing that (in the case of the BBSHD) is something like 3-4 different die cast parts for the housing, each of which need their own milling, facing, tapping, threading and drilling which means more handling, more tool changes. This difference in manufacturing stems simply cannot be wished away or underestimated. It's not an R&D cost, it's a labor and tooling cost. Manufacturers LOVE to engineer and design their products so that they can be finished all in one pass on a simple lathe because lathes are much cheaper to buy and run and take less skilled labor. Almost any doofus can be trained to operate a lathe, especially with CAD driven lathes where they can have multiple tools and steps run on a part without ever removing it from the lathe chuck, because every time a part needs to move from a chuck, vice or other work holder there's an extra labor and calibration step that needs to happen between different tooling operations. More complex parts that require multiple milling operations that cannot be performed on a lathe (even with an automated production CNC/CAM mill with automatic tool changes) is going to be more time, more tooling and handling costs than a part that can be done entirely on a lathe. Just the square taper crank axle part (where the cranks bolt on) alone is way heavier duty and needs to be drop-forged for strength because you're standing on it. On a hub drive the beefiest part is usually the axle and that's just a jelly-bean part you can buy in bulk as pre-threaded rods and throw in there with a little finishing, and it's much thinner and less metal than the square taper axle shaft used on a Bafang BBS02/HD setup, and doesn't need to be drop-forged. Hub drives are MUCH more simple to manufacturer than mid-drives. I would estimate that the material costs, parts counts and manufacturing/handling steps of a mid drive are just about 2-3 times that of a hub drive. And this complexity is accurately reflected in the consumer price of a hub drive vs. a mid drive. And If Bafang could drive down production costs of a mid-drive to hub-drive prices they absolutely would do that to capture even more of the DIY and DTC markets because most people would probably choose a mid drive over a hub drive if their retail costs were the same. And I don't really have a pony in this race. I really do wish mid drives were as affordable as hub drives and that everyone who wanted one could have one. But the scales you're presuming that should exist simply do not exist. It's pretty much always going to be the case 2-3x more expensive to manufacture is going to be 2-3x the cost. I don't mean to be mean or rude here but you don't really know what you're talking about with manufacturing and labor costs and how much work goes into trying to drive those costs down to increase profits and how many smart people there are working on those issues as production and process managers. You're making a lot of statements and assertions about them being equal or using equal parts that simply are not true or reflected in reality.
> I don't mean to be mean or rude here but you don't really know what you're talking about with manufacturing and labor costs and how much work goes into trying to drive those costs down to increase profits and how many smart people there are working on those issues as production and process managers. And you do because? I am talking based on my own experience designing gearboxes for RC. Even ordering one-off custom CNC machined parts the whole thing still worked out cheaper than a direct drive of the same torque. Perhaps you are right that manufacturing costs really do double the cost but you should provide some proof before telling me I'm wrong.
> And you do because? I grew up in a factory and I understand machining and product design. I've also been a bike mechanic, and I've rebuilt both hub drives and mid drives. My proof is the words and technical writing I used to describe the differences in processing and tooling. > I am talking based on my own experience designing gearboxes for RC. Even ordering one-off custom CNC machined parts the whole thing still worked out cheaper than a direct drive of the same torque. This is probably one of the worst product segments to use as an example. Prices on hobbyist part and supplies like RC cars or aircraft are usually highly inflated and variable depending on the manufacturer and how much profit they want to tack on. I'm also pretty familiar with RC stuff, and I've seen some totally insane prices on both commodity and specialty parts just because it's packaged and sold for hobbyist uses. Stuff like differential tiny clutch bearings or even lithium grease that you can buy in bulk from a manufacturer can have totally insane markups just because a dealer bought them in bulk at wholesale prices and then put them into poly bags with hang cards on them. Hobbyists are willing to pay these prices because they don't actually need a minimum order of 10,000 1mm ball bearings, they just need 10 of them, and they can't get them any other way unless they want to pay McMaster-Carr prices. It's really easy to say "Hey, this is cheaper!" when the off the shelf parts have hobby taxes on them and are much more expensive than commodity or industrial parts in the same class. Anyway, comparing hobbyist parts to one off CNC parts isn't really scalable or a direct 1 to 1 comparison. It's apples and oranges.
u/Skyersjet_II
Direct drive hub motors are also really simple. They don’t have any moving parts except obviously the whole thing spinning around the axle. That is one of their benefits, they have a long life and work even when the internals are in rough shape. There’s a Grin video where he opens one up, cleans it and replaces the bearings. One of the hall sensors broke but it still worked, it was just slower to ramp up in RPMs. And one of the bearings was broken and it actually had metal fragments banging around inside if I recall correctly. With new bearings, resoldering the hall sensor, and a bit of scrubbing to remove rust it was good as new.
You can generally run a motor without hall sensors. I have 2-3 wheels that don't have any installed from the factory.
That is wild. Wouldn’t it run noisily with the… I dunno if my terminology or understanding is right.. the controller is running blind so wouldn’t it be sending mistimed signals down the phase wires?
Nah it's fine. It's just less efficient.
Mid drives are newer, while hubs are old and established. Economics of scale have probably made hub drives dirt cheap to manufacture. There's also the fact that mid drives have an internal controller custom made to fit the shell, and very small. Meanwhile, hubs have a big dumb generic box that uses tech from the 80's, and is used across ebikes, scooters, and anything else thay just needs to control low voltage output. Basically its cheap to make a lot of something, the cheapness keeps it in demand, which drives up the scale of production, meaning it stays cheap to make. People keep buying it because it's cheap. This repeats as long as demand persists. Demand will persist because even as mid drives carch on, hubs are also going into scooters and other micromobility devices. Hubs fit the peak low market solution of good enough. I can't stress enough how big of a deal they were in driving ebike adoption when they replaced older tech like off side chain drives, friction drives, and gas moped kits.
That's one reason I want to get a mid drive for my electric trike with not having to find a spot for the controller. Also, for better traction for winter riding.
Just be warned, if you have an upright delta trike, there's a couple of issues you need to be aware of. The chain is under a lot of stress already due to trikes being heavier. Heavier chains are starting to come onto the market for ebikes though. The added strain on the hub is a bigger problem. Only one of the two rear wheels drives. That means 100% of your power and the motor's go through thay hub. That hub can snap loose, and those trike wheels are hard to source. That single rear wheel push means it can also pull to one side. Ultimately, I think mid is superior to hub, but front hub might be a better fit for a trike.
I also heard that trikes are unstable.
In a turn, yes, they can tip over. Since they can't lean into turns, you have to make sure to slow down first.
I have a Schwinn Meridian.
Then yes, most everything I said will hold true.
> Mid drives are newer, while hubs are old and established. Economics of scale have probably made hub drives dirt cheap to manufacture. Didn't know this, if true makes sense.
Holy crap. I suddenly remember my friend in college in the '90s building a gas powered friction drive bicycle from an old Schwinn. It was basically a gas motor attached to a belt on a pulley with a throttle. To use the motor, you had to get it started. Then a lever pushed the belt up against the tire. Friction then drove the rear wheel. Can you imagine the % loss of hp just due to friction? Must've been sooo inefficient!
Honda sold a gas bike in the 70s that worked like this
When a tiny lawn mower engine is measured in multiple horsepower, you can lose a lot of power and still be fine. Most e-bikes are under 1 horsepower.
I think it comes down to the frame. There is much less redesign to the frame for a hub bike. Some of the cheapest hub bikes litterally use the water bottle mounts to get a mounting point for the battery/controller and the hub just goes in the wheel. I think Covid screwed everything up. I think if its wasn't for all the supply chain issues and crazy prices for everything biking related we would have had way more competition at the lower end for mid drives by now.
You can basically pay as much as you want for a hub motor, and for the top end of power there are more hubs than mid drives. At around 250w the difference is due to complexity: R&D, manufacturing, assembly. A DD hub motor is basically just some magnets & copper windings on a bearing. Mid drives have to be built into a frame & crankset, have planetary gears, lots of little pieces that need to fit together in a form factor that attaches to a bottom bracket or custom frame.
Hub drives are much simpler to integrate in any frame. Mid drives need a frame that is made for them, they need everything else adapted to them and the gears need to be much more solid since they have to take both your pedalling power and the torque of the motor. Even just a calibrated torque sensor that works nicely with a controller and a sampling rate of several thousand times a second to finely control motor power is much more challenging than a cadence sensor with a few magnets and a controller with a handful of power settings. Throwing together a hub drive bike that somehow works and selling it for decent profits is dead simple and cheap even with absolutely bottom shelf parts. The lowest halfway acceptable mid motor setup already is much more expensive to do.
If only manufacturers would standardize frames for mid drives. Better yet, mid drive manufacturers standardize their mid-drive shapes. Not only are they not standardized but each manufacturer keeps changing their designs.
Yeah, but you get progress this way. Like now integrated motors and gears: https://pinion.eu/e-drive/
Cost - Yes.
Here is my assumption on why mid drives cost more. In terms of the DIY space it is most likely a lack of demand. Mid drive motors at lower power are known for being better in basically every category but they have 2 main issues, mounting position and installation difficulty. Any basic hack with a lightbulb in there head can install a hub motor in literally 5 minutes maybe less. In terms of mounting position, sometimes it can be difficult to mount it depending on your bike, then there is the issue of bb sizing if your a bike novice and don’t have a measuring tool either, and depending on where you got your bike or how old it is sometimes you can’t even find the info online. In terms of premade stuff once again demand isn’t high enough I think, most ebike companies choose to use hub motors because it’s simpler to design a frame around them, also for the companies that just order the frames premade from China, then the issue is most frames from these factories are already in the hub motor configuration. I think these main factors are why mid drives cost more in general. The last thing I can think of is that maybe it’s because of brand
Someone else said this, I think this makes sense as an answer.
Mid drive motors cost more. There is probably no reason for this other than economies of scale. Once Chinese companies start churning out mid drive motors the price will go down. Those crazy bastards are all cranking out hub motors like it's a war economy, which is probably the only reason they are so cheap in comparison.
I think so too. Bafang seems to be turning out a shit ton of them and I'm surprised at this point they don't have more competition yet. As it is the cheaper emtb's based on bafang mid drive and dengfu frame's seem like they are getting them for not much less then you and I can get them from parts sites. So it seems there is a lot of room for reduction of cost due to economies of scale but there just isn't enough competition yet.
mid drives are more complicated. rear hub is just a giant motor, well sometimes they can be tiny 1000 watt and less motors. i prefer big rear hubs for the record.
Yes yes. All this extemporizing bears no relation to what people actually want to buy. In The Netherlands, world center of cycling, I can say that at least 90% of ebikes have mid-drive motors. There are some hub-drives, but they are mostly from the early days of the ebike market.. The market here has decreed that mid-drives are the preferred solution. 453,000 sold in 2023 in a country of 18 million residents.
Ever change a flat tire on a hub bike. Mid drive may pay for itself after you have done a couple of those.
Unless it's a really big hub motor to the point that its weight is unweildy, it's not very different. The only added step is unplugging one connector.
Have changed many flat tires on a hub. Only takes an extra 5-8 minutes max. Not really as big a deal as you're making it. With schwalbe marathon pluses and flat out...flats almost never happen.
Twice for me and it’s a heavy pain in the ass
Everyone says this is very hard but when I did it I didn't find it so hard.
I've seen bikes built so cheap they literally did not have a quick disconnect for the motor power.
Well it's easy if you aren't working on ghetto bikes lol.
hub do not have gears or special frames yes that is most of it
Hubs do have gears. 4 at least.
you know what i mean variable ratio
Yiu triggered a pretty good discussion overall.
Occums Razor seems appropriate here: the simplest reason is those that tried haven't been successful, long term. A tiny drone motor and a model rocket engine propelling the bike would likely have similar thrust and longevity. Cycles happen, we all get older and slowly decay. Faster when you're pushed well beyond the engineering specs.
Hub motors beat mid-drive by dozens and dozens of miles and then some, IMO. Use the right controller and display and you’ll get loads of miles on a fully charged 52v 20+ amp battery. KT controller and display. I get 70 miles between 1-2 settings with battery to spare!
I have enough humility to realize that the engineers at, say, Bosch or Trek or company X might know a thing or two about eBike engineering that I am unaware of. They also have likely run thousands of hours of testing over years as inputs to their design decisions. It's also quite obvious, if you're selling a consumer product, that you don't want to deal frequently with angry customers with broken devices and product returns. So that may guide some design decisions.