Class 1 vs 3

[rich c]

What most people just don't realize is that mid-drives when riding at higher speeds do suffer a mechanical efficiency issue due to gearing. Everyone knows that when climbing in low gears they get the job done but lets say you are on a 44T front and an 11T rear sprocket 75% of the torque at the crank (rider + motor torque) is lost due to gearing. This is the same reason a car needs to downshifted when going up steep grades.

This is where so many sales staff are ignorant. They don't realize that if someone does want to spend a lot of time commuting at 20-28mph a hub drive ebike is probably a better solution because the torque is transmitted directly to the rear wheel so at higher speed their overall efficiency will typically be much better than a mid drive and the speed easier to retain by the rider.

Don't expect anyone associated with Bosch, Yamaha, Brose, etc. to tell you this when buying an ebike with their drive system and ebike sales staff rarely have an understanding of gear ratios and mechanical efficiency.

How does the Bosch with an 18 tooth chain ring and internal gear ratio figure into your hypothesis? I didn’t think any Bosch used a 44t chainring.

 

[Scott Adams]

lets say you are on a 44T front and an 11T rear sprocket 75% of the torque at the crank (rider + motor torque) is lost due to gearing. This is the same reason a car needs to downshifted when going up steep grades.

This is where so many sales staff are ignorant.

Don't expect anyone associated with Bosch, Yamaha, Brose, etc. to tell you this when buying an ebike with their drive system and ebike sales staff rarely have an understanding of gear ratios and mechanical efficiency.

I'm guessing they won't tell you this not because they are ignorant, but because it doesn't matter.

The chainring to sprocket torque loss on a pedal only bike is identical, it has nothing to do with the motor.

You might recall that work = force x distance. Likewise work / energy is conserved from the crank to the sprocket (with a minor mechanical loss of a few percent.)

You're simply trading force for distance, which is what mankind invented gears for.

 

[GregGritton]

How does the Bosch with an 18 tooth chain ring and internal gear ratio figure into your hypothesis? I didn’t think any Bosch used a 44t chainring.

Bosch actually reports "equivalent torque" on their motors with the small chain rings. Thus, while Bosch claims 65Nm of torque for the older Performance Line motors the actual torque is 65Nm/2.5 = 26Nm. However, this torque gets multiplied when connected to a larger gear in the rear. For example, with a 34t rear gear and a 18t chain ring the torque is multiplied by 34/18, so your final torque is 26Nm*34/18=49Nm. The 49Nm should be comparable to a hub motor.

The advantage over hub motors with the same torque rating is that, when operating at low speeds but using low gears, a mid-drive will still be in an efficient cadence range, so the motor is operating efficiently, not using too much power, nor producing very much heat. A hub drive at low speed will operate less efficiently, turning a lot of power into heat. At higher speeds both will operate efficiently.

The 2020 motors (except the Bosch Performance Line cruise) use the larger chain rings. I wouldn't be surprised to see Bosch bikes use 44t chainrings. With a quick check I find the Trek Verve+ 2 comes close, at 38t, and it is only a 20mph bicycle.

 

[Amazer98]

How does the Bosch with an 18 tooth chain ring and internal gear ratio figure into your hypothesis? I didn’t think any Bosch used a 44t chainring.

I think all the Bosch motors use largish chainrings (38-46 teeth), except for the current Speed motor, which is now being replaced by the new model, which uses a large chainring. The current Speed motor uses a small (18-22 teeth) chainring that spins 2.5x per crank revolution.

 

[Rick53]

I think all the Bosch motors use largish chainrings (38-46 teeth), except for the current Speed motor, which is now being replaced by the new model, which uses a large chainring. The current Speed motor uses a small (18-22 teeth) chainring that spins 2.5x per crank revolution.

So is it possible to Buy let's say a Verve + and down the road change the ring and or the Motor(More Power Faster)

Another thing I don't understand : If you are a Rider who pedals on average just 10 MPH Topping out at around 15 MPH on flats 50-55 Cadence: On Something Like a Verve + . Are you going to ever be able to pedal a fast enough cadence to take advantage of a 28 MPH Motor?

 

[Amazer98]

So is it possible to Buy let's say a Verve + and down the road change the ring and or the Motor(More Power Faster)

Another thing I don't understand : If you are a Rider who pedals on average just 10 MPH Topping out at around 15 MPH on flats 50-55 Cadence: On Something Like a Verve + . Are you going to ever be able to pedal a fast enough cadence to take advantage of a 28 MPH Motor?

Rick,

I am pretty sure that you can't swap a different model motor on a given bike, as the size and shape (and probably the mounting points) of each motor model differs. That said, there are bikes like the new Trek Allant that have various versions; some come with the Class 1 Bosch motor and others come with the Performance Speed motor, so the factory has obviously included adapter plates for certain motors or else built the frames somewhat differently to adapt to each motor's design.

As I mentioned earlier, I ride with a Class 3 Bosch motor. I don't need to pedal with a fast cadence to reach 28 mph. On the flats, I simply shift to a higher gear (i.e., one of the smaller rear sprockets) to pedal along at whichever cadence I want; the higher the gear I pick, the slower the cadence. This works just like a regular road bike, except the assist of the motor enables me to go faster (i.e., shift into a higher gear than I normally would want to use).

Similarly, when I climb a hill, I downshift as I would on a regular road bike. But I usually do not have to downshift to quite so low a gear as I would on an acoustic bike. Instead of going to my 'granny gear' (the largest rear sprocket), I might be in 2nd, 3rd or 4th gear. The assist of the motor enables me to do this, and thus I can climb up the hill faster and with less pressure on my knees.

I personally like to pedal at a brisk cadence, but not super-fast like some cyclists. I enjoy the aerobic exercise, and adjust the assist level (usually between Eco and Tour) depending on how hard a workout I want at the moment or how fast I want to go.

The thing to keep in mind is that you absolutely do not need to pedal at a particularly fast cadence to take advantage of a 28mph motor. The Speed motor does deliver its power most efficiently when you pedal about 60-70 rpm or faster, but that's not overly brisk. You don't really want to climb hills with a super low cadence-- it's tougher on the knees and not good form. But you don't have to spin like the devil to take full advantage of the motor either.

 

[AHicks]

Ken, I really like my set-up and find it plenty powerful enough...

That's the bottom line right there.

I would add that 5:1 gearing, or variable gearing as found on the mid drives, have a more universal appeal for those with one bike and various riding applications. For those justifying their bike's existence based solely on it's ability to commute longer distances over relatively flat land, the DD is going to be tough to beat.

 

[Deleted member 4210]

Ken, I don’t fully buy into your premise that mid-drive motors deliver only 25% of their power (i.e., torque) to the rear wheel. For example, I ride a 52 lb. bike with a Bosch Performance Speed motor with peak torque of 62nm.

That would mean that a maximum of 15 or 16nm torque could be sent to the drive wheel, right? But, of course, I’m not riding at full power all the time. In fact, I’m almost always in Eco or Tour mode... so that implies I’m accessing, what, maybe 8 or 9nm, I would think.

That certainly sounds minimal to me. Yet I can say that Eco gives me a notable boost and Tour lets me really crank up sizable hills at a good clip... so wouldn’t you agree that’s kind of impressive for some small spare newton meters ? And on the flats, the motor also gives a very decent boost... in Eco I pedal happily at 21-23mph, and in Tour I settle in at 26 or 27... so the boost is definitely there at the higher speeds.

I can only conclude that you’re somewhat exaggerating the power drain of using a mid-drive system. I’m sure hub motors have their advantages, but I really like my set-up and find it plenty powerful enough... and the newly upgraded Speed motor is 20% more powerful, so...

Ken is absolutely correct. And no mid drive ebike OEM discloses what the actual power is that is transmitted at the wheel. The rpm curve vs torque on these very high speed motors, that internally have a lot larger gear ratios, really impacts where you will feel the power. The top end is terrible. Plus they are typically operating at only 250 watts, and worse only 36 volts, whereas the hub drive motors are easily found with 500 to 750 watts, and 48 volts to allow much higher current to flow to way more powerful magnets. Yes mid drives in of themselves are 'efficient' in squeaking out as much as they can from 250 watts, but you are not going to get the high torque and power at the wheel at high speeds.

For example you could, with enough gears, and right sprocket sizes, have a 100 watt motor eventually get you up to a speed of 28 mph, but you would do it very slowly and likely require a lot of human effort to do that.

The other problem with mid drives, even when they can be built to operate at higher voltages and higher watts, like a Bafang BBHSD, is transmitting that amount of power from the crank back through the chain and cassette just literally rips the heck out of those drive train elements.

But the mainstream OEM mid drives such as Bosch, Brose, Yamaha, and Shimano, operating at low wattages and lower voltages are comparatively rather weak through most of the speed ranges when you get above 15 mph. They are fine for Europe which is where speeds are limited to 15 mph, and where most of the mid drives are sold, but they are doing a real marketing number on unsuspecting riders here in America, spouting highly irrelevant torque numbers and acting like those are apples to apples with hub drives. They aren't. Longer term people are asking for long term trouble on reliability attempting to use mid drives if they desire to maintain speeds over 20. It's gonna bite them on not just external drivetrain issues, and internal bearings and gears.

Not much more than 7 years ago, mid drives had numerous reliability and durability issues that made several oems pull back, and take their product off the market. People have short memories, or simply were not aware of ebikes back then here in the US, and while improvements have been made, it's no joke that Bosch was forced to come up with a field kit to address the outboard bearing issues that have happened so frequently it forced them to do that. And worse it was in warranty, meaning it happened way too soon in the lifecycle of those motors.

Then there are the issues of frame design and motor mounts, that continue to cause cracked frames at that juncture of the ebike, and lots of 'creaking' and torsional issues that transmit up through the frames. Design wise from a mechanical engineering standpoint, putting a motor at the crank, where a lot of torque needs to be generated to overcome drive train losses, move the ebike and human, and the forces generated by the rider, his weight, (worse if he or she stands such as for mtg use) and the 3 points of the frame meeting at that intersection, makes it one of the worst locations to place a motor. Besides there is very little space to work with in terms of width at the crank, and especially maintaining ground clearance. Sure it can be engineered to do a certain amount but we still see far too many of the aforementioned issues occur time and again, no matter the brand. So not only is it costly upfront on the purchase price to design for this, but longer term the maintenance costs will be a lot higher. Stiff price to pay, to get 'efficiency' and weak power at higher speeds.

It's physics and materials and mechanical engineering, and reaching the limits of what can be done with so many constraints at that location for the motor. Opinions of this don't matter. If you disagree it merely means you don't have sufficient engineering background to understand what is going on. Sorry to be so blunt.

 

[Amazer98]

If you disagree it merely means you don't have sufficient engineering background to understand what is going on.

Maybe ignorance is bliss, at least in this instance. I know there are an equal number of arguments against hub motors, so I won't regurgitate them here.

In my case, I was looking for a Class 3 gravel grinder-style Ebike, something with drop bars, medium-wide tires and hopefully a front suspension. I found all three in the Bulls Grinder Evo (the Giant Road-E+ Pro was a contender), but nothing else came close. No rear hub drives in this segment.

Anyway, I noticed you were taking the Bosch, Brose and Yamaha mid-motors to task for being too weak... yet also criticizing them for exerting too much force on the frame and powertrain. All I can say is that the system delivers all the power I want; I seldom want to use the higher power assist settings anyway.

Time will tell if the wear and tear is unreasonable. I expect to replace my chain more often, but I think with proper shifting and non-abusive riding practices, I should get very decent performance and durability.

 

[rich c]

Maybe ignorance is bliss, at least in this instance. I know there are an equal number of arguments against hub motors, so I won't regurgitate them here.

In my case, I was looking for a Class 3 gravel grinder-style Ebike, something with drop bars, medium-wide tires and hopefully a front suspension. I found all three in the Bulls Grinder Evo (the Giant Road-E+ Pro was a contender), but nothing else came close. No rear hub drives in this segment.

Anyway, I noticed you were taking the Bosch, Brose and Yamaha mid-motors to task for being too weak... yet also criticizing them for exerting too much force on the frame and powertrain. All I can say is that the system delivers all the power I want; I seldom want to use the higher power assist settings anyway.

Time will tell if the wear and tear is unreasonable. I expect to replace my chain more often, but I think with proper shifting and non-abusive riding practices, I should get very decent performance and durability.

I didn’t change my chains on 2 different 2016 speed XDURO Haibikes until 2,500 miles. Cassettes were fine and they now have 3,000 miles on them. So short life drivetrain is really based on riding style and NOT just because you own a mid drive! Same goes for brakes. Still on original pads.

 

[Browneye]

Just got my Yamaha mid-drive and see that I can hit the cutoff at 20 VERY easily. So there's no easy way to unleash the class-3 with it??
I don't really need or desire to go that fast, but sure would be nice to not have the ceiling so low.

 

[Rick53]

Maybe ignorance is bliss, at least in this instance. I know there are an equal number of arguments against hub motors, so I won't regurgitate them here.

In my case, I was looking for a Class 3 gravel grinder-style Ebike, something with drop bars, medium-wide tires and hopefully a front suspension. I found all three in the Bulls Grinder Evo (the Giant Road-E+ Pro was a contender), but nothing else came close. No rear hub drives in this segment.

Anyway, I noticed you were taking the Bosch, Brose and Yamaha mid-motors to task for being too weak... yet also criticizing them for exerting too much force on the frame and powertrain. All I can say is that the system delivers all the power I want; I seldom want to use the higher power assist settings anyway.

Time will tell if the wear and tear is unreasonable. I expect to replace my chain more often, but I think with proper shifting and non-abusive riding practices, I should get very decent performance and durability.

For someone like me : I am 64 Just 6' tall long arms : In really good physical shape. But a realist > I have 64 year old joints that spent 30 years or more dirt biking a lot > I currently own a Dual Sport and a Verve Both By Trek. I enjoy both Bikes . Although the Verve is more comfortable on longer rides : No interest in Drop bars : Have been looking at the Vado > I may hold off an hope Trek makes a Verve in class 3. If I were to buy right now I'd probably want a Class three Bike similar to what you mention . Just with Upright bars vs Drop :

At least from what I have researched the vado or maybe Trek Alliant seem to be My choices: Trek told me the allaiant will have an option in class 3 with front Shock and possibly options for no fenders : I know Specialized makes the como : But what I see on Youtube it looks like a Granpa Bike with smaller tires :

I also doubt that even with an E-bike That I would be using it more then 600 miles in the short 5 month sometimes 4 month season Michigan offers

 

[indianajo]

The advantage over hub motors with the same torque rating is that, when operating at low speeds but using low gears, a mid-drive will still be in an efficient cadence range, so the motor is operating efficiently, not using too much power, nor producing very much heat. A hub drive at low speed will operate less efficiently, turning a lot of power into heat. At higher speeds both will operate efficiently.

This entire discussion is fact free about hub motors. Mike excepted. Statements made previously appear to pertain to DD hub motors. Hub motors come in 2 varieties, direct drive and geared. DD motors are great at high speeds on flat terrain. Geared have internal gears that make the rotor turn multiple times for each wheel turn. Thus geared hub motors are as good on hilly terrain as mid-drive, but won't generally go as fast as DD. DD shed heat better than geared hub motors thus though inefficient are better for long sustained heavy grade in areas like the Sierra & Rocky mountains.
If one doesn't like the wall built in CL 1 bikes at 20 mph, build a kit on an existing bike. I bought 1200 W geared HM with PAS for $221 and 1000 W DD no PAS for $189. Kits have escaped the nanny states regulations, mine have no speed limiter at all. I frequently hit 35 mph downhill, saving the momentum to keep from dragging down to 4 mph uphill.

 

[Amazer98]

If I were to buy right now I'd probably want a Class three Bike similar to what you mention . Just with Upright bars vs Drop :

Rick53,
I’m 66, so my joints are older than yours. If you’re looking for a bike like mine with flat handlebars, check out this model:

(Link Removed - No Longer Exists)

Bulls has a few other similar Class 3 models as well.

 

[e-boy]

I wish they would but I doubt Trek will make a Verve + class 3 . But maybe up a notch to the Active Line Plus . (50Nm vs 40)
I test rode that bike and loved it , but it was way too underpowered .
I could live with 20 mph , but the gentle power curve and low torque didn't work for me .
Too bad ; other than that it's a beautiful bike .
It could also benefit from a suspension fork .

 

[Rick53]

For someone like me : I am 64 Just 6' tall long arms : In really good physical shape. But a realist > I have 64 year old joints that spent 30 years or more dirt biking a lot > I currently own a Dual Sport and a Verve Both By Trek. I enjoy both Bikes . Although the Verve is more comfortable on longer rides : No interest in Drop bars : Have been looking at the Vado > I may hold off an hope Trek makes a Verve in class 3. If I were to buy right now I'd probably want a Class three Bike similar to what you mention . Just with Upright bars vs Drop :

At least from what I have researched the vado or maybe Trek Alliant seem to be My choices: Trek told me the allaiant will have an option in class 3 with front Shock and possibly options for no fenders : I know Specialized makes the como : But what I see on Youtube it looks like a Granpa Bike with smaller tires :

Rick53,
I’m 66, so my joints are older than yours. If you’re looking for a bike like mine with flat handlebars, check out this model:
View attachment 40466

(Link Removed - No Longer Exists)

Bulls has a few other similar Class 3 models as well.

I have looked at this bike : I was basically thinking Trek or Specialized because the LBS have them : And if I really needed service they are there. Although I do all my own on a non e-bike . The specialized VADO does set higher then Treks alliant : Plus it's longer reach like I'd prefer

 

[Ken M]

Ken, I don’t fully buy into your premise that mid-drive motors deliver only 25% of their power (i.e., torque) to the rear wheel. For example, I ride a 52 lb. bike with a Bosch Performance Speed motor with peak torque of 62nm.

That would mean that a maximum of 15 or 16nm torque could be sent to the drive wheel, right? But, of course, I’m not riding at full power all the time. In fact, I’m almost always in Eco or Tour mode... so that implies I’m accessing, what, maybe 8 or 9nm, I would think.

That certainly sounds minimal to me. Yet I can say that Eco gives me a notable boost and Tour lets me really crank up sizable hills at a good clip... so wouldn’t you agree that’s kind of impressive for some small spare newton meters ? And on the flats, the motor also gives a very decent boost... in Eco I pedal happily at 21-23mph, and in Tour I settle in at 26 or 27... so the boost is definitely there at the higher speeds.

I can only conclude that you’re somewhat exaggerating the power drain of using a mid-drive system. I’m sure hub motors have their advantages, but I really like my set-up and find it plenty powerful enough... and the newly upgraded Speed motor is 20% more powerful, so...

It's not a power drain .... it's all gearing physics. If the gearing didn't have an impact on the torque to the rear wheel every car and bike would be a single gear ratio. If you ride a non electric bike and say put it in 1st gear and go all out for a few seconds you will accelerate much faster then if you did the same in say 8th gear and the reason is that less of your power (via the torque transmitted thru the gearing) reaches the rear wheel.

There is another issue that impacts all electric motors - stall torque is maximum and torque reduces as a factor of back emf as the motor spin speed increases.

You comment about the performance "on flats" is telling because sustaining 25mph on a flat requires about 10nm (400w) so most EU spec'd mid drives will provide in that ball park thru gearing but when going up just a 4 percent grade the torque goes up to 22nm (800w) and most riders will not sustain that speed for long on a mid drive. Better chances they will on a hub drive because the motor may have enough dynamic torque.

Keep in mind that the tire diameter has a large role in how an ebike performs. It's why the 20" folding models make riders feel like they can super accelerate.

 

[Bicyclista]

Just got my Yamaha mid-drive and see that I can hit the cutoff at 20 VERY easily. So there's no easy way to unleash the class-3 with it??
I don't really need or desire to go that fast, but sure would be nice to not have the ceiling so low.

Get a BikespeedRS dongle to unlock the speed restriction. It works very well and preserves all the display info correctly, except for maximum speed attained (it displays an overly optimistic 55 mph!). However, it will probably void your warranty. I got mine when the warranty was about to expire and have been using it for the past 3 years without issue on my Yamaha-powered bike.

 

[Ken M]

How does the Bosch with an 18 tooth chain ring and internal gear ratio figure into your hypothesis? I didn’t think any Bosch used a 44t chainring.

In my opinion, Bosch was really smart going with the smaller front chain rings and spinning it at 2.5x rider cadence to simulate the results of a larger chain ring. There is obvious advantages when just cruising at higher speeds. There are a lot of factors to realized performance and I'm not sure if Bosch publishes an accurate/honest dyno test of any of their motors. There was another motor manufacturer that was going to to the same thing but with an even higher cadence multiple at 3 x rider cadence. If I were buying a mid drive ebike that was going to be used primarily for urban riding I would certainly put the Bosch motors with the smaller front chain rings at the top of my list.

Here's the problem. Most of their motors were still going on enthusiast mountain ebikes where having multiple front chain rings may be important to overall performance. Some riders want reasonable cadence at higher speeds so a 18T front at 2.5 X is only equivalent to a 45T front which to some may be restrictive.

 

[jim6b]

Is it time to shut up and let's race?

Surely, someone has been settling these matters on the track.