Torque rating on E-bikes - marketing gimmick?

[J.R.]

EMBN has a dynamometer, in the UK they call them a Rolling Road. I haven't seen them do a lot with it since it debuted 2 months ago.

 

[evolvable]

Later this summer, I will gather "hot-selling" E-bikes with 5 or 6 different drive systems and put them on a Dynamometer, and make a video of the testing for our YouTube channel.
This will provide a deeper understanding of the "Torque ratings" and debunk some of the myths.

1. Bosch Gen4 motor - do you get 85Nm of torque and at what RPM?
2. Yamaha PW-X2 - 80Nm and they claim zero-cadence assist but is 80NM produced at zero cadence? at power level?
3. The same goes for Shimano E8000, E7000
4. Bafang Ultra - does it provide 160Nm or is it a marketing gimmick?
5. Finally, Brose's claim of 90 NM

The E-bike market is so new that with savvy marketing some of the real numbers are masked but knowing these numbers will empower and educate the end-user in a positive way.

Holy cow, this is awesome. I can't wait to see the results!

 

[Johnny]

There is already such a thing and the data is not presented to the public.

Dynamometer for pedelecs - EMEC PROTOTYPING GmbH

The customer is Germany’s largest bicycle manufacturer and a leader in the eBike market. Several hundred thousand bicycles and eBikes are produced at the North German site.

www.emec-prototyping.com

Whatever the drive system manufacturers claim, if it can be replicated on a dynamometer, then it is valid, or else, it just some marketing term.
If they claim 150 Nm and the Dynamometer shows 60 Nm, then there is something wrong there. Tuning of cars or motorcycles using Dynamometer is a common thing. We may have to adjust the parameters for bike's weight and tire contact area in the Dyno machine but it provides deeper insight than just looking at the graphs.

Something similar to this one was what I had in mind but I was not sure if you had access to it. It is perfect, especially for mid drives which report the torque at the crank. If I am not mistaken it can replicate precise torque input by the rider right?


Even if you have access to a regular dyno like the first one only, I think the following setup will work pretty well.

1. Install some accurate pedal based torque sensor.
2. Use the gear which will make the chain line as straight as possible.
3. A fit rider such as yourself riding the bike at the maximum possible assist level so that you can force the motor to run at its peak at all times.
4. Now you ride at a wide cadence range then get the data from the wheel dyno and the power meter pedals.

At this point once you sync the two data, since tire parameters and gear ratio is known , assuming around %97 drivetrain efficiency (since the chain is straight this efficiency number should be accurate), one can easily compute the total generated power and torque at the crank. By subtracting the rider power which is computed by the pedal based torque sensor you should reach a pretty accurate peak rpm/torque graph for the mid drive itself.
One advantage of this setup is you only need to carry the power meter pedals between the bikes.

Looking forward to this.

 

[Petropoliskhan]

Later this summer, I will gather "hot-selling" E-bikes with 5 or 6 different drive systems and put them on a Dynamometer, and make a video of the testing for our YouTube channel.
This will provide a deeper understanding of the "Torque ratings" and debunk some of the myths.

1. Bosch Gen4 motor - do you get 85Nm of torque and at what RPM?
2. Yamaha PW-X2 - 80Nm and they claim zero-cadence assist but is 80NM produced at zero cadence? at power level?
3. The same goes for Shimano E8000, E7000
4. Bafang Ultra - does it provide 160Nm or is it a marketing gimmick?
5. Finally, Brose's claim of 90 NM

The E-bike market is so new that with savvy marketing some of the real numbers are masked but knowing these numbers will empower and educate the end-user in a positive way.

Hi Ravi, much of the technical results/ jargon will be way over my head and my question will possibly demonstrate how little I understand this stuff but would it be be relevant/ possible to add some rear hub motors ( Stromer (tdcm) , Bafang, Dapu, Gmac) to this test? Would this be representative and illustrate by the numbers what many of us have experienced on the road ?
As always, thank you for your work informing , educating.

 

[Ravi Kempaiah]

Hi Ravi, much of the technical results/ jargon will be way over my head and my question will possibly demonstrate how little I understand this stuff but would it be be relevant/ possible to add some rear hub motors ( Stromer (tdcm) , Bafang, Dapu, Gmac) to this test?

Thanks for this note. I will certainly add as many drive systems as possible to the list. What we are trying to do here is to educate the E-bike community and take them on this journey of exploration and understanding.

The E-bike market is quite new and as a result, it provides room for all kinds of misinformation and false marketing claims but very soon as the market matures, those marketing gimmicks won't stand.
One of the marketing tools used by E-bike drive system manufacturers is touting torque ratings that are outright ridiculous.
For example, one Chines manufacturer claims 160Nm of torque, and anyone with a basic understanding of engineering mechanics realizes that pushing that kind of torque through a bike chain is irresponsible or there is something wrong with the physics and the numbers are completely off.
Mid-drive manufacturers try to woo customers to their product quoting outrageous torque numbers and make the hub motors look bad but as a Stromer ST5 owner, you know that Stromer has perhaps more oomph than many other bikes. This marketing vs. experiential gap needs to be explained clearly and that is what we are hoping to do.

These companies may quote 100+ Nm but on the Dynamometer, at the wheels, if that numbers is replicated, then it is valid. Or else... their marketing would sound something like this
A man tries to seduce a woman quoting 1Million/year salary but when she tries to verify, he says, "oh, my salary is actually $1Million but by the time it hits my bank accont, it is $60K/year "

If 100Nm of torque is produced at the crank but by the time it hits the tires/road, it is 30 Nm, then something is clearly not right here in the marketing material.

One of the popular electric motorcycles in the U.S is Zero motorcycles and they use a 34kW mid-motor (45x more powerful than Stromer motor) and they still quote a Torque value of 106 Nm and now you see what I am trying to convey here.

Review: 2019 Zero FXS is the low cost electric motorcycle field's best kept secret

The Zero FXS electric motorcycle is the most affordable and (in my opinion) the most fun offering in the Zero...

electrek.co

 

[Petropoliskhan]

Thanks for this note. I will certainly add as many drive systems as possible to the list. What we are trying to do here is to educate the E-bike community and take them on this journey of exploration and understanding.

The E-bike market is quite new and as a result, it provides room for all kinds of misinformation and false marketing claims but very soon as the market matures, those marketing gimmicks won't stand.
One of the marketing tools used by E-bike drive system manufacturers is touting torque ratings that are outright ridiculous.
For example, one Chines manufacturer claims 160Nm of torque, and anyone with a basic understanding of engineering mechanics realizes that pushing that kind of torque through a bike chain is irresponsible or there is something wrong with the physics and the numbers are completely off.
Mid-drive manufacturers try to woo customers to their product quoting outrageous torque numbers and make the hub motors look bad but as a Stromer ST5 owner, you know that Stromer has perhaps more oomph than many other bikes. This marketing vs. experiential gap needs to be explained clearly and that is what we are hoping to do.

These companies may quote 100+ Nm but on the Dynamometer, at the wheels, if that numbers is replicated, then it is valid. Or else... their marketing would sound something like this
A man tries to seduce a woman quoting 1Million/year salary but when she tries to verify, he says, "oh, my salary is actually $1Million but by the time it hits my bank accont, it is $60K/year "

If 100Nm of torque is produced at the crank but by the time it hits the tires/road, it is 30 Nm, then something is clearly not right here in the marketing material.

One of the popular electric motorcycles in the U.S is Zero motorcycles and they use a 34kW mid-motor (45x more powerful than Stromer motor) and they still quote a Torque value of 106 Nm and now you see what I am trying to convey here.

Review: 2019 Zero FXS is the low cost electric motorcycle field's best kept secret

The Zero FXS electric motorcycle is the most affordable and (in my opinion) the most fun offering in the Zero...

electrek.co

View attachment 84970

Hi Ravi. I am eagerly awaiting your results. I'm clearly not an engineer type ( I have a really hard time with math stuff) so it is my hope that there will be some layman explanations.
Hopefully the data produced by your setup will shed some clarity/objectify/put some numbers on what is usually only described through experience/feeling and silence some of the bad faith arguments... (I won't hold my breath!)
Obviously there are many reasons, vested interests why such an endeavor will be frowned upon by manufacturers and sales people bound by contractual obligations and fanboys (and fangirls (see the IOS vs Android debated).
You are to be commended for doing this and sharing your findings publicly while trying to do business with some of these manufacturers.

 

[Johnny]

The problem is, the claim of 160nm may be correct and it still will not mean anything without rpm.

A 90kg rider, putting its weight on one feet while standing on the bike, given a crank arm length of 17.5cm, will generate 155nm of torque! Unless that rider can rotate the pedals while keeping that torque, it will go no where.

Take a 50nm mid drive, increase reduction reduction ratio 3 times and you get 150nm. But supported cadence a 3rd of what it was before.

In the end what matters is how much power converted to motion at the wheels. Nothing more.

 

[Ravi Kempaiah]

Later this summer, I will gather "hot-selling" E-bikes with 5 or 6 different drive systems and put them on a Dynamometer, and make a video of the testing for our YouTube channel.
This will provide a deeper understanding of the "Torque ratings" and debunk some of the myths.

1. Bosch Gen4 motor - do you get 85Nm of torque and at what RPM?
2. Yamaha PW-X2 - 80Nm and they claim zero-cadence assist but is 80NM produced at zero cadence? at power level?
3. The same goes for Shimano E8000, E7000
4. Bafang Ultra - does it provide 160Nm or is it a marketing gimmick?
5. Finally, Brose's claim of 90 NM

The E-bike market is so new that with savvy marketing some of the real numbers are masked but knowing these numbers will empower and educate the end-user in a positive way.

Further to this discussion, I thought the recent video from MKBHD was quite insightful.
Interesting that not just E-bike companies but also car companies can advertise these numbers in a misleading way. One of the well-known YouTube tech reviewer, Marques Brownlee (who has interviewed CEO's of Microsoft, Google, Tesla, Apple) released a new video where he talks about Nm-torque ratings and how they can be misleading.
we will put some serious testing effort this summer on the torque ratings.
Last summer was a tough one as we moved to Canada from the US and we have our test facility ready this time.

 

[smitty]

Ravi, do you still have the Stromer 5? And how do you like it, say compared to the ST-2.
I have gone to Reise and Mulluer, but always likes my St-2 and often think about picking up an ST-5
1

 

[MinnBobber]

Ravi, do you still have the Stromer 5? And how do you like it, say compared to the ST-2.
I have gone to Reise and Mulluer, but always likes my St-2 and often think about picking up an ST-5
1

Smitty, I have ST2-S and ST-5. Are you anywhere near Minnesota as you could try when the snow is gone.
I think both are flagship models.
I was thinking of starting a post on ST2-S vs ST5?
You had ST2, not ST2-S?
MinnBobber

 

[bluecat]

we will put some serious testing effort this summer on the torque ratings.

I'm very curious on this; especially, if it is possible to determine torque values at travel speed.

We had an annoying debate about the miraculous battery capacity and energy consumption of an AirTag. People wants to believe what the Tech Leaders tell them. So they believe in Hydrogen powered trucks, even when they just rolling down from a hill. They believe in µLiter full screen blood tests juste when an attractive Lady claims this.... Thx for sharing the video

 

[williamrothman]

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 but the torque sensor on some of these mid-drives suck!

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

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