Torque rating on E-bikes - marketing gimmick?

[J.R.]

But before that can happen, consumers need to have better information available to inform themselves abo

I agree. That's the point I was trying to make earlier in the thread. It's all about reliable information one can use to compare ebikes across the market. Manufactures cherry pick what suits them best and they offer little comparative evidence to backup their claims. Most of it is truly the opposite of empirical evidence. You won't convince everyone because people get wedded to certain brands.

 

[bluecat]

You can not have your top of the line model less adjustable than a lesser model, that is a design flaw.

Hmm, but they did.

You can fit the Macan with a roof box and many other things and none of them will fit on the Carrera 4S. Is this a problem for a 911-no-turbo-customer? Of course not; and not the other customers is it only a hypothetical problem.

The BMC Teammachine SLR01 ONE costs about 11'500 CHF. This almost twice the price of a Alpenchallenge AMP. And it has definitely less equipment.

But it's the Stromer forum her, so lets come back to the most expensive Stromer ever. Those people who want to commute in a superior way, will buy it. But I agree, the best selling Stromer at the time is the ST1. Nice price, many different stems and handlebars - and a Stromer.

 

[Johnny]

Hmm, but they did.

You can fit the Macan with a roof box and many other things and none of them will fit on the Carrera 4S. Is this a problem for a 911-no-turbo-customer? Of course not; and not the other customers is it only a hypothetical problem.

The BMC Teammachine SLR01 ONE costs about 11'500 CHF. This almost twice the price of a Alpenchallenge AMP. And it has definitely less equipment.

But it's the Stromer forum her, so lets come back to the most expensive Stromer ever. Those people who want to commute in a superior way, will buy it. But I agree, the best selling Stromer at the time is the ST1. Nice price, many different stems and handlebars - and a Stromer.

I am talking about adjustment to fit the rider. If you like to stick with your 911 analogy, it does have steering wheel and seat adjustment!


Let's take this to Stromer forum and not derail from the subject of this thread.

 

[bluecat]

Let's take this to Stromer forum and not derail from the subject of this thread.

Yes, please.

The connotation in this thread title is: "How is it possible to beat all these mid drives with their extra-high torque values on the daily commute with a Stromer?"

The answer is rather simple: A mid drive motor has to overcome the drivetrain. The make torque values of mid drives comparable with those form hud drives, you need three parameters:

1. torque measured in NM
2. rpm of the motor at measuring point
3. speed of the eBike at measuring point

 

[Johnny]

When you see motorcycle engine specs, they usually say something like "65Nm@12,500rpm" (I'm talking about gas engine)

Yes, same with cars and even this is incomplete information since we have only a finite number of gears the motor will not stay at 12500rpm all the time. That is why, to tell the whole story, you need a Torque or Power vs rpm graph. Dynos are very informative in that sense.

Ebike companies give peak values without the rpm it is achieved which is even worse than motorcycles/cars. Then you see everyday people talking about meaningless peak torque numbers.

 

[bluecat]

That is why, to tell the whole story, you need a Torque or Power vs rpm graph.

It seems, you have forgotten, it's about bicycles. You have to pedal on such vehicles. And as a human being, the possible range of cadence is narrow. That's why the third parameter is important: Speed of the eBike.

At the end, the result will be: Hub drives have higher torque values on higher speed, mid drives have their best values on low speed.

 

[Johnny]

...
At the end, the result will be: Hub drives have higher torque values on higher speed, mid drives have their best values on low speed.

You can not come to that conclusion.

On paper a mid drive, given no drive-train losses and the right gear ratio exists, will be no worse than a hub motor of the same power output no matter the speed.

 

[bluecat]

You can not come to that conclusion.

But I did - because of my experience with my Stromer over the past 10 years: Never could a mid drive compete with my Stromer - and all these Bosch & Brose have much higer torque values then my Stromer.

 

[Johnny]

But I did - because of my experience with my Stromer over the past 10 years: Never could a mid drive compete with my Stromer - and all these Bosch & Brose have much higer torque values then my Stromer.

the problem is you are trying to generalize your experience with specific brands to all hub/mid drives.

On the other hand my experience is similar to yours and what you can conclude from your experience is Torque values by themselves don't give enough information about performance.

The motors you mentioned are both below Stromer's nominal value even at their peak. A fair comparison is probably between a Bafang ultra fitted with a nice controller like @pushkar s offerings.

 

[bluecat]

The motors you mentioned are both below Stromer's nominal value even at their peak.

Interesting statement; according the technical specifications my Stromer has a torque of 25NM. Which mid drive motor - mounted in a street legal 45 km/h ebike - has less?

 

[Johnny]

Interesting statement; according the technical specifications my Stromer has a torque of 25NM. Which mid drive motor - mounted in a street legal 45 km/h ebike - has less?

I am referring to power btw. Still,

Hub motors' torque is measured at the wheel since they are directly connected to the wheel.

Please read my previous example but one last time here it is.

Bosch mid drives gen 2/4 have around 600W peak power, assuming that you can transfer all the power to the rear wheel without any loss,
at 20mph the rear wheel turns around 240rpm and it translates to 23.87nm at the wheel ,
at 25mph, wheel rpm is around 300rpm and the torque at the wheel will be19.1nm!

 

[bluecat]

Bosch mid drives gen 2/4 have around 600W peak power, assuming that you can transfer all the power to the rear wheel without any loss,
at 20mph the rear wheel turns around 240rpm and it translates to 23.87nm at the wheel ,
at 25mph, wheel rpm is around 300rpm and the torque at the wheel will be19.1nm!

Sorry, I can't follow. I see no way to comfrom Power to Torque through calculation.

If you start with Power and then removing Time you get Work. Now you can remove Distance and you will end up with Weight.

The key point is Work is not Torque even if the physical symbols looks similar.

 

[Johnny]

Sorry, I can't follow. I see no way to comfrom Power to Torque through calculation.

If you start with Power and then removing Time you get Work. Now you can remove Distance and you will end up with Weight.

The key point is Work is not Torque even if the physical symbols looks similar.

I don't know where you are getting the claim of work = torque that is wrong and no one claims that.

Power of a rotating object can be calculated by torque times angular velocity. RPM is just a translation of Angular velocity, 1 rpm = 6 degrees/second which is the unit of Angular velocity.

So if you have the information on two of power,torque,rpm then you can compute the third variable. In the previous post that is why I always give you power and the rpm that power is achieved.

If you are still confused take a look at how rotational kinetic energy is derived, any elementary physics book will have it .

 

[bluecat]

I don't know where you are getting the claim of work = torque that is wrong and no one claims that.

It comes from school, a long time ago.

Id did check now, how today's opinion is: https://de.wikipedia.org/wiki/Drehmoment#Maßeinheit

Die Einheit der mechanischen Arbeit ist ebenfalls das Newtonmeter. Dennoch sind Drehmoment und Arbeit unterschiedliche physikalische Größen, die sich nicht ineinander umrechnen lassen, weshalb man die Einheit der Arbeit als Joule bezeichnen darf, diejenige des Drehmoments aber nicht.

 

[J.R.]

This is a very good topic and a well reasoned discussion. I'm sorta giving the topic a bump for new shoppers we see every year at the start of riding season. So many get caught up in the hype of numbers pushed by the sellers. Seems more important than ever to test ride if you can.

Enjoy the ride!

150 Newton meters of torque:



160 Newton meters of torque:



170 Newton meters of torque:

 

[George S.]

I don’t know why anyone believes any of the ebike numbers. The problem is that there are a lot of variables. Rather than sorting this stuff out, the marketing tends to dwell on certain ‘magic’ numbers. Reviews seem to make things worse.

Range and top speed are very popular numbers. Both are rather bogus. The obvious way to do range is to calculate the watts being consumed and determine the total watt hours in the battery pack. Start with the pack capacity. You can hook the pack to a load and run things through a watt meter that keeps track of total watts, watt hours. Of course, most packs have ‘special’ connectors so doing a test load may be more difficult.

If I know that my pack has 500 watt hours, it’s all going to come down to the watts that are being consumed. That will determine range. If I say that I go 20 mph and use a steady 300 watts, I can go 500/300 or 1.67 hours, and that works out to 33.4 miles of range. But, pick a speed, and you get a different watt reading. Saying an ebike has a range of 30 miles is absolute rubbish. Find a speed where you get 30 miles, is all they are saying. Beyond this, it’s hard to say how much fat tires really cost you, in terms of range. Rolling resistance probably matters. How much work does the rider really do in ‘assist’ modes? What is the riding position? All the numbers are basically garbage. It’s not rigorous set of procedures. You could profile a bike based on tires, rider position, all that.

Somebody would have to make the case for torque. It’s not like diesel trucks and big trailers. If I want to climb hills, I get a mid-drive where I have gears to produce climbing power. Relying on torque and a hub motor might work, I don’t know. I think reviewers should have test hills and use a verifiable procedure to say how well a bike climbs real hills. Is the torque number a good measure? I don’t even have a guess. Torque must have some impact on starting on a hill. I guess. Test a bike on a steep hill where you stop in the middle and try to get going.

 

[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.

 

[Johnny]

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.

What kind of a setup do you have in mind?


1-2 and 5 have some graphs on the net for their peak torque/rpm, I expect the claimed peak values to be somewhat accurate.

 

[theemartymac]

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.

That one will be youtube click gold! Make sure it's monetized, lol

I have no doubt that the Bafang Ultra (I have one) is not truly anywhere near 160nm in any factory assembled configuration, but I also suspect the standalone motor is possibly capable of it in a bench application with no limits placed on it by firmware or hardware (i.e. not battery powered). But since I can't keep it plugged into the wall the whole time, that's a bunch of classic marketing crap.

It would be nice to also see what the actual torque of say the best Luna Hot Rodded Ultra kit could be as a more achievable representation of it's potential in an actual practical(-ish) build.

 

[Ravi Kempaiah]

What kind of a setup do you have in mind?


1-2 and 5 have some graphs on the net for their peak torque/rpm, I expect the claimed peak values to be somewhat accurate.

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.