Torque rating on E-bikes - marketing gimmick?

[bluecat]

I'd also be willing to bet that 99% of these motors coming out of China don't meet any QA or consistency specs, and that they probably did a one time measurement, or even calculated theoretical torque rating when they first designed the motor 1 or 2 decades ago.

In terms of Stromer, the motors are built in Formosa and engineered in Switzerland.

One reason, why a test drive is very useful: Mid-drives are sensitive to your pedaling cadence - a hub drive is sensitive to the speed of the bike.

This is because the efficiency of every motor depends on its rpm. You should ride your Stromer between 20km/h and 45 km/h. But if you do this like at Tour de France or if you prefer the lazy way - it doesn't matter for the motor. Even Stromer keeps the torque charts secret. But for sure, the curve does not looks like a downhill. We can assume, Stromer adjusted the curve (by controlling the Ampere vs. rpm) to looks like Ayers Rock.

 

[Rusty in Austin]

Who is this girl with 36DD? (JK)

No, kidding! The last thing I really, truly understood was the comparison of the two girls. . . These guys are making my head spin. I thought I knew what to look for as I'm going about, preparing to buy my first electric bike--my choice being the 2018 Haibike Sduro Trekking 9.0 with the Bosch powertube. . . Seems like it has all the torque I'd need for the hills in and around Austin.

But then what do I know, other than the difference between a B and DD cup.

 

[JRA]

I personally pay about as much attention to the advertised nm values as I do the range estimates that the manufacturers are using as marketing tools. The suggestion to try as many bikes as you can in the terrain you expect to ride in is really the best way to go if you are really concerned about your requirements being met, but quite frankly we are talking about +/- 1hp here so it's not like any legal e bike is going to be pulling stumps out of the ground.

Keep in mind that all hub motors, geared and dd, can be wound for torque or speed values and any combination in between. Although most don't offer much more than a middle version. A wound for torque geared hub motor will have the most torque and a dd hub motor wound for speed would be most efficient for that purpose. So in other words dependent on your requirements and also wheel diameter, you have a choice to make when deciding on one. The PAS system you choose also plays into this as it relates to the controller settings and the way the modes are set to the torque/speed values.

Mid drives have not only the ability to work through the bikes drivetrain but they have a gear reduction system within the motor housing. This serves to reduce the motor armature output which is a high rpm so that by the time it gets to the cranks it provides the reduction necessary so that it will work in congress with conventional bike gearing systems. This is achieved in different ways by the manufacturers. Take for example why Bosch has such a small chain ring and Yamaha has large chainrings yet both advertise similar nm ratings.

Some systems give you access to program, either by a cable or an app, the different levels of assist. What this is essentially doing is dividing the speed and torque values via the controller. In this way you can help to optimize the efficiency of the system based on how you expect the bike to perform. Which means that although there is such a thing with any system as maximum nm of torque you probably won't be at that threshold until the motor is at its maximum output setting for torque but at the same time burning the wh candle at both ends. It seems most put more value on range than torque anyway and that is all in how you control the bike in whatever environment you are riding in.

Also Grin's testing is done as scientifically as anyone does it and they have no agenda that I can see. If they get a different value, with say a Stromer motor, than Stromer I would have to go with them.

 

[jazz]

I have been studying E-bike drive systems for sometime now. I find it amusing that so many people just go by what they read in the brochures. Especially, the Torque ratings!
Yet the subjective experience is nowhere near to the corresponding values. To put in crude, vulgar terms, It is like you're courting a girl and you decided to pursue her because this girl has 32B, 36DD.. etc

Torque rating is just one of the parameters and how the overall system is designed is much more important than one single parameter. The algorithm, controller design, power draw etc matter more than just "Torque". A system could have more torque but at what expense? power? less speed?

Bosch - 60Nm and now upped to 70Nm.
Derby Impulse 2.0 - 80Nm (newer RS versions)
TranzX mid drive - 73Nm
BBS-02 - 120Nm
M1 Pin Drive - 120Nm
Dapu - 40Nm
Currie electro drive - 42Nm
Stromer SYNO drive - 35Nm

I could go on...

Why is it misleading?

I have called tech people and even those who design the drive systems to find out how they measure these Torque ratings and the response was appalling. They have no clue!!

Is this measured at the wheels?
at the derailleur? (if so, is it amplified because of gears?)
at the hub?

Out of all mid-drives I have tested only two systems stand out in terms of Torque ( BBS-02 and M1 Pin dirve), rest have been very subdued experience.

You run any of the mid-drives at 23mph on a slight incline (3-4% grade) and see the range! and compare it to efficient hub drives. You won't notice any difference and in fact, given the specs, you'll see far less range than advertised.

Mid-drives supposedly get more range because they make you work like donkey. The mid-drives don't over exert and are extremely conservative in terms of power output (exception of few mid-drives I mentioned above).

So, all I can say is -

Beware of bombastic sounding blowhard people (if it's me, so be it). Is the claim backed up with some real data that can be verified? Is that a credible source?
Most importantly , test drive several bikes. Take it out for extended 24 hour test drives and put it through some vigorous testing. It's worth it. You'll learn a lot and not yield to marketing gimmicks.

Anyhow, the point is to educate yourself. At the end of the day, all you want is reliable E-bike to do 30 mile rides? most bikes would suffice. If you're a geek like me, you'll want to tear it apart and keep learning

Enjoy

Yea Torque NM ratings are B.S. The Bafang BBSHD lists at 160 NM which is more than my Zero SR with 660amp controller and double my Empulse R electric motorcycle ....yeah right!

 

[bob armani]

No, kidding! The last thing I really, truly understood was the comparison of the two girls. . . These guys are making my head spin. I thought I knew what to look for as I'm going about, preparing to buy my first electric bike--my choice being the 2018 Haibike Sduro Trekking 9.0 with the Bosch powertube. . . Seems like it has all the torque I'd need for the hills in and around Austin.

But then what do I know, other than the difference between a B and DD cup.

LMAO-As soon as the DDs come into play, heads start turning and spinning and everything is thrown off kilter. LOL

 

[Ravi Kempaiah]

Reading torque ratings on marketing material makes me smile in amusement!

One of the popular Yamaha motorcycles marketed in India is this model called FAZER 25. The bike retails for $1875 and sells in hundreds of thousands...

https://www.yamaha-motor-india.com/motorcycle-fazer25.html



It has a 250cc engine and produces 20Nm of torque. Their PW-X motor is supposed to put out 80Nm! mmm

Somebody missed Physics 101 in their high school

Here is a protip for new E-bikers... if someone tries to convince you that such and such a bike produces 75Nm or 90Nm or torque instead of recommending a test ride first.. then they are bluffing. Don't get primed by numbers, just ride it and see how you like it.

 

[Trail Cruiser]

Ebike's torque is measured differently compared to ICE (internal combustion engines) and other big electric motors.

On ICE's and other large electric motors, such as that of the Tesla, the torque is measured at the crank shaft, or main shaft (that, we understand).

On hub drives, the torque is measured at the wheel, regardless if it is direct drive or geared drive (still understandable).

Here's the interesting part, on mid drives, the torque is measured at the pedal crank. We know that a typical ebike motor is geared down by 20-30 times. For example, a Brose is geared down by 30x at the crank, a Bafang BBSHD is geared down by 21.9x, and so on...

When it comes to mid drive ebikes, you have to multiply the ratio back up to get the motor's original torque from the motor's main shaft. The torque changes in the same proportion as the gear reduction ratio. Either way, the power stays the same.

I hope I'm not making things more confusing.


One more thing, German and Japanese brands will mention "nominal" values as their rated values. On the other hand, Chinese brands and other off brands will mention the "peak" values as the rated values and then advertise that their products have more torque and more power than the competition.

 

[Ravi Kempaiah]

Ebike's torque is measured differently compared to ICE (internal combustion engines) and other big electric motors.

On ICE's and other large electric motors, such as that of the Tesla, the torque is measured at the crank shaft, or main shaft (that we understand).

On hub drives, the torque is measured at the wheel, regardless if it is direct drive or geared drive (still, understandable).

Here's the interesting part, on mid drives, the torque is measured at the pedal crank. We know that a typical ebike motor is geared down by 20-30 times. For example, a Brose is geared down by 30x at the crank, a Bafang BBSHD is geared down by 21.9x, and so on...

When it comes to mid drive ebikes, you have to multiply the ratio back up to get the motor's original torque from the motor's crank. The gear reduction ratio changes in the same proportion as the torque. Either way, the power stays the same.

I hope I'm not making things more confusing.

Not trying to be aurgementative. It doesn't matter hub drive or mid drive, when you stamp on the pedals, how quickly does the bike propel you? That's all that matters. If there are fine prints like "You have to be in this gear, on this incline at this temperature..... wearing this color undies.." then you know those numbers don't mean much.
There is no standardized way to measure these numbers...

There is one proven test i.e., Dynamometer testing. If Bosch or Brose claim such numbers (to sell their units in millions), they should be open enough to provide a video to show what torque the dyno is seeing.

 

[Trail Cruiser]

The mid drive makers can vary the gearing ratio to the extreme so they can play the "numbers game" of higher torque output.

For example, the earlier Yamaha (with similar power rating as the Bosch) has higher torque rating. However, that was attained with more down gearing. In effect it's upper cadence range is 80 RPM, and then beyond 80 RPM there's no more assist from the motor. On the other hand, the Bosch had lower torque but the assist continues up to the 120 RPM cadence.

It's similar to a car's transmission where one is in 2nd gear (Yamaha) and the other is in 3rd gear (Bosch). The first has more torque but has lower speed, the later has lower torque but higher speed. Either way, both have the same power.

 

[Ravi Kempaiah]

One more thing, German

They will do whatever it takes to promote their brand nicely!
Ever heard of Volkswagen Diesel scam? One of the largest car maker in the world lying blatantly and then paying $$ Billions in fine?

 

[TForan]

Both of these Bafang motor are rated at the same maximum torque.

 

[Trail Cruiser]

Both of these Bafang motor are rated at the same maximum torque.

The Bafang Ultra and the Bafamg BBSHD have the same power and torque rating.
(Link Removed - No Longer Exists)
(Link Removed - No Longer Exists)

The right side of the picture that you posted show the Bafang Ultra but left side is not a Bafang BBSHD. That picure is that of the less powerful BBS01 or BBS02.



The BBSHD has embedded magnets inside the rotor to reduce parasitic magnetic flux and allow faster rotational speed.

 

[AlanDB]

I don't even know what the torque numbers are on my bike and I don't care. All I know is when I step on the pedals the assist feels natural and powerful enough (I normally ride in Eco mode). When I get to a steeper hill, I bump the assist level up a notch or two and I feel like superman!

 

[Trail Cruiser]

Not trying to be aurgementative. It doesn't matter hub drive or mid drive, when you stamp on the pedals, how quickly does the bike propel you? That's all that matters. If there are fine prints like "You have to be in this gear, on this incline at this temperature..... wearing this color undies.." then you know those numbers don't mean much.
There is no standardized way to measure these numbers...

There is one proven test i.e., Dynamometer testing. If Bosch or Brose claim such numbers (to sell their units in millions), they should be open enough to provide a video to show what torque the dyno is seeing.

I see your point that these ebike performance has to be measured by a third party, independently, and dynanometer tested for real-world mechanical torque and power (not theoretical calculated numbers, derived from amps and volts).

Especially the Torque. Mechanical torque is measured as pound feet, how much force (in pounds) applied to a rotational radius of 1 foot.
1 lb-ft = 1.355 817 N-M.

For some reasons, people are calculating torque from electrical watts output (not from mechanical watts). And this is where most of the misconception arise since electrical watts is not the same as the mechanical watts. You have to consider the conversion factor or efficiency factor. And these numbers vary.
Torque (N.m) = 9548.8 x Mechanical Power (W) / Speed (RPM).

Those power meters on your ebike's display are showing electrical watts (volts x amps) and not mechanical watts (Torque x rpm x delta).

The only way to know the real numbers of mechanical, actual, and tangible torque and power is to dyno test it.

Either way, many reputable ebike makers want to downplay their performance ratings so they can pass many countries that limits to only 250 watts. So most likely, they would derived their figures from actual performance at the wheel (by dynamometer). In that way, all the efficiency losses from the battery loses, electrical loses, to the friction at the gearing, and chains, and tires are factored in. The net measurement will show a very low number compared to the motor if it is tested alone, separately.

To the contrary, many Chinese kits and other off brand ebikes will tell you that they have higher power and torque than the competition and they have the proof to show (Volts x amps stamped on the ebike or stamped at the kit).

We know better, we cannot compare the two by their claims. They have to be tested on the road side by side, or tested at the dyno.

 

[TForan]

I can leave mine in top gear and ride just about anywhere. That's torque.

 

[Ravi Kempaiah]

An amusing example:

Yamaha mentions 80Nm torque for their PW-X system (which is a very good system by the way)

PW-X2

High end sports motor

global.yamaha-motor.com

What is amusing is their motorcycle MT-09 is reported to have 82Nm of torque!
Either one of them is true but not both. May be the way torque numbers are reported for E-bikes is flawed. There is no way an e-bike motor of the size of palm put out a torque that can yank 2 humans effortlessly.

Yamaha MT-09 - Wikipedia

en.wikipedia.org

 

[bluecat]

What is amusing is...

... what happens on the road!

A few days ago, I've met a all new Specialized Turbo Vado 45km/h mid-drive e-bike. Before the uphill part, I let him pass. Sporty rider with typical race-clothing. He showed me what his mid-drive can give. It was very easy for me to follow him with my 10 years old Stromer which provides only 25 NM torque. On the plain again, I came closer to read the values from the clumsy display on his handlebar: 31 km/h and rising. I could beat him everywhere even without switching to POWER-mode.

Now tell me what torque values Brose/Specialized is claiming...

 

[J.R.]

An amusing example:

Yamaha mentions 80Nm torque for their PW-X system (which is a very good system by the way)

PW-X2

High end sports motor

global.yamaha-motor.com

View attachment 40186

What is amusing is their motorcycle MT-09 is reported to have 82Nm of torque!
Either one of them is true but not both. May be the way torque numbers are reported for E-bikes is flawed. There is no way an e-bike motor of the size of palm put out a torque that can yank 2 humans effortlessly.

Yamaha MT-09 - Wikipedia

en.wikipedia.org

View attachment 40187

As a lifelong motorcyclist, who's had motorcycles tested on a dynamometer, I can say your statement is fact! I have to say though, the auto and motorcycle industry also floats fantasy numbers. Real world power at the rear wheel never comes close. Motorcycle people talk about "stump pulling power" of 100 ft.lb of torque and higher. 100 ft.lb. is about 135 Nm.

Ebike companies claiming 80 to 100 Nm is just fantasy. Ebikes have "weed pulling power". I love 'em, but it's true.

 

[Rick53]

Everyone suggests Test riding as many as you can : Where can someone Living In Michigan do that ? There's no such place : What someone living in a Big City would experience with an E bike is totally different then where I live. It's not all country but most of your riding is.

 

[Mass Deduction]

An amusing example:

Yamaha mentions 80Nm torque for their PW-X system (which is a very good system by the way)
[...]
What is amusing is their motorcycle MT-09 is reported to have 82Nm of torque!
Either one of them is true but not both. May be the way torque numbers are reported for E-bikes is flawed. There is no way an e-bike motor of the size of palm put out a torque that can yank 2 humans effortlessly.

Torque on a mid-drive e-bike is measured at the crank, whereas with a motorcycle it'd be measured... where exactly? That makes a huge difference to what the number is purporting to mean.