My Thoughts on Mid Drive..Hub Drive and Throttle

[Ken M]

I can think of two things.

The strongest argument is that mid-drives, all other things being equal, can climb steeper hills.

The somewhat less strong argument is that a mid-drive uses fewer watt-hours per mile, so you can go further on a given battery charge.

At slower speeds mid-drives do have an efficiency and typically a torque advantage vs a direct drive hub but the torque advantage may not be there vs a geared hub drive.

I think so much of an ebike's performance is perceived during slow hills climbs and from 0 to say 12mph that mid drives tend to get all the performance praise, but if you ride your ebike for commuting and tend to spend a lot of your riding time closer to 32kph / 20mph you should really consider a higher power rated direct drive hub motor or a somewhat lower rated geared hub motor.

The simplicity of a direct drive hub motor should not be ignored if you want a super reliable ebike.

 

[Mr. Coffee]

At slower speeds mid-drives do have an efficiency and typically a torque advantage vs a direct drive hub but the torque advantage may not be there vs a geared hub drive.

I think so much of an ebike's performance is perceived during slow hills climbs and from 0 to say 12mph that mid drives tend to get all the performance praise, but if you ride your ebike for commuting and tend to spend a lot of your riding time closer to 32kph / 20mph you should really consider a higher power rated direct drive hub motor or a somewhat lower rated geared hub motor.

The simplicity of a direct drive hub motor should not be ignored if you want a super reliable ebike.

Well, I live at the top of a steep hill and I haven't found hub drive bike that can successfully make the climb.

Honestly, though, I am an extreme case. But I suspect you are as well. Over half of the auto trips in the Untied States are ten miles or less, which is the sweet spot for an e-bike. Bluntly, for a trip of ten miles or less most people won't find much difference whether they are riding a class I or a class III or something overpowered that isn't even legal.

 

[Ken M]

Well, I live at the top of a steep hill and I haven't found hub drive bike that can successfully make the climb.

Honestly, though, I am an extreme case. But I suspect you are as well. Over half of the auto trips in the Untied States are ten miles or less, which is the sweet spot for an e-bike. Bluntly, for a trip of ten miles or less most people won't find much difference whether they are riding a class I or a class III or something overpowered that isn't even legal.

My work commute is 18 miles each way so it does help save time if I can sustain a higher speed. I'm not advocating motorcycle-level speeds but I have no clue why the US market has just blindly accepted the EU 32kph/20mph Class 1 assist limit as ideal. There honestly is no reason that 45kph/28mph Class 3 ebikes are so much more expensive (essentially it's a firmware difference) and I don't see an assist speed that high as dangerous when a human road a bike averaging 33mph for an hour.

Most of the hub motor (both DD and geared) are really focused on the Asian and European markets because that is where the economies of scale are. I'm sure a MAC geared hub motor with and ASI controller would provide more than adequate performance for your hill climb and still arguably be compliant to the federal ebike regulation.

I'm not against mid drives as my biggest issue with them is the greater wear they subject the drive system components to. That can be more service costs than most buyers realize.

 

[indianajo]

Well, I live at the top of a steep hill and I haven't found hub drive bike that can successfully make the climb.

So how steep is steep? I can start up 7/8" in 6" grade from a dead stop at 330 lb gross with my 1200 w 48 v geared hub motor. There is a stopsign at hwy 3 that I leave from that is probably steeper.

 

[AHicks]

Well, I live at the top of a steep hill and I haven't found hub drive bike that can successfully make the climb.

Honestly, though, I am an extreme case. But I suspect you are as well. Over half of the auto trips in the Untied States are ten miles or less, which is the sweet spot for an e-bike. Bluntly, for a trip of ten miles or less most people won't find much difference whether they are riding a class I or a class III or something overpowered that isn't even legal.

Re: "haven't found a hub drive that can successfully make the climb."
First, I hate it when people lump all "hub drive" performance together. The thought being that clearly there's a huge difference in the amount of torque available with a direct drive vs. a gear driven rear hub, even with all else being equal. So I have to ask you to expand on your comment for additional clarity. Are you saying a gear driven rear hub production bike advertised at 750w + won't make your hill? A smaller gear drive won't make your hill, or are you including only direct drive hubs in that comment?

Thanks, -Al

 

[Mr. Coffee]

Re: "haven't found a hub drive that can successfully make the climb."
First, I hate it when people lump all "hub drive" performance together. The thought being that clearly there's a huge difference in the amount of torque available with a direct drive vs. a gear driven rear hub, even with all else being equal. So I have to ask you to expand on your comment for additional clarity. Are you saying a gear driven rear hub production bike advertised at 750w + won't make your hill? A smaller gear drive won't make your hill, or are you including only direct drive hubs in that comment?

Thanks, -Al

I said what I said: "I haven't found a hub drive that can successfully make the climb."

I have tried in a Pedego Interceptor and a Rad Mini, as well as a fat tire Juiced Bike with a 750w geared hub motor. My access road has a roughly 750 foot section with grades between 22 and 24 percent, and that section is preceded by a very sharp switchback so there isn't any realistic option to get a run at that section. I suspect if the road was straight and smooth the Juiced would likely make it, but it is unrealistic to make the switchback at much more than 6mph and that pretty much does it.

Also, to be clear, very few people on this forum ride their e-bike in a mountainous area and don't really have any realistic awareness of how steep a road can get and what exactly that would mean. Bluntly, that section of road is pretty frightening to ride down, and extremely scary in wet or slippery conditions.

 

[AHicks]

If I may ask then, what are you using to make this climb?

 

[Mr. Coffee]

If I may ask then, what are you using to make this climb?

2017 R&M Charger GX Rohloff, Bosch Performance CX Drive.

I replace the chain about every 1000 miles, and the front and rear sprockets about once a year.

Brake pads last about 500 miles, and rotors 1000-1200 miles.

 

[Johnny]

I can think of two things.

The strongest argument is that mid-drives, all other things being equal, can climb steeper hills.

The somewhat less strong argument is that a mid-drive uses fewer watt-hours per mile, so you can go further on a given battery charge.

I agree with the first argument but I am skeptical about the second one. Probably at lower steeps mid drive will be more efficient since the cadence can be kept around the optimal band due to gearing however, at higher speeds where the hub motor is turning at its efficient rpm, because of the drive train losses mid drive will be less efficient.



BTW, I think the title of this thread is a little misleading.

 

[Feliz]

As someone who knows nothing about ebikes, I am concerned to know just how much of your post was in jest

I have experience and I'm concerned, and wondering what the intention of the post was

 

[6zfshdb]

I have experience and I'm concerned, and wondering what the intention of the post was

I think everything ebikemom said in her post was in jest. My LBS sells both hub and mid drives. I asked him about this when I was bike shopping. He said he sees little difference in maintenance between the two drive types.

@Feliz , I had a 1969 BSA Lightning almost exactly like the one in your avatar picture. Is the bike yours and do you still own it?

 

[erider_61]

So...the JB Weld repair on the pedal only lasted 3 days. LBS is a joke. 2 weeks to get new cranks and pedals and also no crank pullers in stock for sale. So new plan is to drill from backside of cranks into pedal spindle and then tap and install stainless cap hex bolts and flat washers.

Asked in the store if I could use their crank puller to do this short term repair and they said no, but would gladly pull them for $90 shop charge. WTF...I said I still wanted to buy the crank puller and parts but wanted to do short term repair until the parts came in.

Thinking I will look at local auto place for a steering wheel puller and try that. If it works I will order cranks and pedals online and let the wonderful LBS be stuck with the parts they ordered in. This is the same store that took a week to get an inner tube to repair a flat which I had to do myself because they don't work on ebikes...

 

[AHicks]

2017 R&M Charger GX Rohloff, Bosch Performance CX Drive.

I replace the chain about every 1000 miles, and the front and rear sprockets about once a year.

Brake pads last about 500 miles, and rotors 1000-1200 miles.

From the Bosch web site: https://www.bosch-ebike.com/us/products/performance-line-cx/

Max. torque
"With a torque of up to 75 Nm. For sporty acceleration even in alpine terrain, without changing gear."

Using Grin's motor simulator, I think most will be able to see that the power available in your R&M is not hard to duplicate or exceed using a gear driven rear hub, especially when given the budget you used.

My point is, hub drives, whether you've tried them or not, should not be totally discounted when it comes to climbing a hill. The validity of your comment regarding "hub drives", that likely cost 1/3 or less of the mid drive you are using to compare them to, is questionable IMHO.

I bring this up because I would hate to have a rookie coming along later, who would most likely never consider climbing the kind of grade used in your "benchmark", might be misled with info like that. -Al

 

[AHicks]

So...the JB Weld repair on the pedal only lasted 3 days. LBS is a joke. 2 weeks to get new cranks and pedals and also no crank pullers in stock for sale. So new plan is to drill from backside of cranks into pedal spindle and then tap and install stainless cap hex bolts and flat washers.

Asked in the store if I could use their crank puller to do this short term repair and they said no, but would gladly pull them for $90 shop charge. WTF...I said I still wanted to buy the crank puller and parts but wanted to do short term repair until the parts came in.

Thinking I will look at local auto place for a steering wheel puller and try that. If it works I will order cranks and pedals online and let the wonderful LBS be stuck with the parts they ordered in. This is the same store that took a week to get an inner tube to repair a flat which I had to do myself because the don't work on ebikes...

Not a fan of the LBS in our area either, though I will try them if looking for a part in a hurry. If I hear "we can have it for you in a day or 2", I tell them that I can do that too. Then I go to Amazon. Most anything you need in the way of parts, or tools, available there at reasonable prices with quick delivery.

 

[indianajo]

Thinking I will look at local auto place for a steering wheel puller and try that.

I tried that on my Pacific Quantum. The gap between the pedal arms and the shaft boss was too thin to get any of my 6 pullers in. The tie rod puller with a pointed end couldn't force it off either, started bending the shaft under the hammer blows.
Since my 1200 W 48 v ebikeling geared hub motor will start 330 lb on a 15% grade, that is 73 nm torque.
13" radius wheels, 330 x .15 x (13/12) x 1.36
since it will go faster if I hit that grade at >10 mph torque is higher at the higher speed than at the 4 mph it ends up at from a dead stop.
I get annoyed too about everybody comparing mid drives to "hub motors" on hills. Bike motors come in 2 classes, geared motors & direct drive motors. Whether the gears are in a hub or mid-drive is immaterial.
None of my bikes multiply torque with the sprockets, they only multiply speed. The lowest sprocket ratio I have is 32:32 or 1:1. If one had a torque multiplying allfine or roloff IGH with a 1:1 sprocket ratio one might get torque multiplication, but usually those hubs have about a minimum 42:18 sprocket ratio or 2.3:1. Most mid-drives don't allow multiple front sprockets, although the yamaha allows 2 sprockets. With a front geared hub motor I have 3 front sprockets on my bodaboda, 52, 42, 32.
One wonders whether the bosch 75 nm is at the motor sprocket, or at the wheel. If at the motor sprocket one would have to divide by 2.3 or so to get torque on the back wheel. The idea that the bike sprocket set gives torque multiplication is laughable.

 

[tomjasz]

I think everything ebikemom said in her post was in jest. My LBS sells both hub and mid drives. I asked him about this when I was bike shopping. He said he sees little difference in maintenance between the two drive types.

@Feliz , I had a 1969 BSA Lightning almost exactly like the one in your avatar picture. Is the bike yours and do you still own it?

Wow! I have routine lubrication maintenance on all my mids, I’ve never done anything with my DD Hub.

 

[tomjasz]

I can’t imagine owning a bike and not having basic tools. Especially a crank puller.

BUT, $90? THAT LBS SUCKS!!

 

[HonoraryOrange]

From the Bosch web site: https://www.bosch-ebike.com/us/products/performance-line-cx/

Max. torque
"With a torque of up to 75 Nm. For sporty acceleration even in alpine terrain, without changing gear."

Using Grin's motor simulator, I think most will be able to see that the power available in your R&M is not hard to duplicate or exceed using a gear driven rear hub, especially when given the budget you used.

My point is, hub drives, whether you've tried them or not, should not be totally discounted when it comes to climbing a hill. The validity of your comment regarding "hub drives", that likely cost 1/3 or less of the mid drive you are using to compare them to, is questionable IMHO.

I bring this up because I would hate to have a rookie coming along later, who would most likely never consider climbing the kind of grade used in your "benchmark", might be misled with info like that. -Al

I think the one thing hub drives will never have is the gear multiplier. I think, generally speaking, they're quite good for most any application. But one place that a mid drive will always win is that huge incline where you're in your granny gears, they're just too much of a force multiplier on a good bike.

 

[indianajo]

. But one place that a mid drive will always win is that huge incline where you're in your granny gears, they're just too much of a force multiplier on a good bike.

Hilarious myth disproved by mathematics. Count the smallest front and largest rear sprocket. Divide front by rear. That is speed multiplication. Reciprocal is torque division. From the pictures I see very few 32 by 32 out there on mid drive bikes. 42:28 might be probable, which decreases torque by .66.
There is torque multiplication from the small sprocket on the mid drive motor to the big one that drives the crank. After the crank torque is decreased or at best, even.

 

[Alaskan]

Not a fan of the LBS in our area either, though I will try them if looking for a part in a hurry. If I hear "we can have it for you in a day or 2", I tell them that I can do that too. Then I go to Amazon. Most anything you need in the way of parts, or tools, available there at reasonable prices with quick delivery.

Supporting Amazon is supporting the destruction of the community in which you live. They make no donations to local events, local teams or local charities. They are destroying the retail sector in communities across the world. I would rather pay a bit more, wait a few more days and support my neighbors than give my trade to a hungry giant that is eating our society alive all for what? The convenience of one click?