Stromer torque measurements compared to other brands

[AvalancheRun]

Stromer bikes are typically claimed to have 35 nm to 45 nm of torque. At face value, these numbers are low for heavy e-bikes.

I test rode an ST3. It flew on the flat from 0-28 mph in seconds, and climbed up a parking structure effortlessly (and more silently than any other e-bikes I've tested by ....miles). The method by which they measure torque is obviously very different from other manufacturers.

Is there a way to compare these to Specialized/Bosch/etc. mid drive torque figures? Asking because I am looking at Stromers on upway and wondering how the ST1 will perform up steep hills (10-12% grade)

 

[Stefan Mikes]

Torque without the rotational speed simply means nothing It is the max mechanical motor power that counts. The published figure for the CYRO Drive II is 35 Nm at 670W. The reference rotational speed of the rear wheel is then 670/35 = 19.14 rad/s or 183 rpm.
-----------------
It's the theory. If we, however, check what the 183 rpm actually means for the wheel size expected from Stromer ST1, it would only mean around 23 km/h e-bike speed, which you know is far higher in real life! Something stinks here. I would then drop the "torque" reasoning completely and just concentrate on the specified max motor power.
-----------------
Stromer does not explain whether the published 670 W is the electrical or mechanical power. If that's the mechanical power, ST1 is a powerful e-bike. If that's the electrical power, the actual max mechanical motor power would be around 520 W, which is the same as your 85 Nm mid-drive motor.
-----------------
Your experience was a high acceleration rate on the flat. Correct. Stromer ST1 motor is a Direct Drive (not internally geared), which has the full torque at zero speed. DD motors love spinning fast and achieve the high efficiency at the high e-bike speed. However, the same feature makes them hopeless climbers. The reason being your e-bike speed would drop dramatically on a steep climb; as the motor rotates at the rear wheel speed, the motor would get into the slow spinning rate, making it highly inefficient, and releasing a lot of heat. That is a know phenomenon, leading to overheating or sometimes melting the motor (if the thermal protection is inadequate).
-----------------
I have configured a version of ST1 that would satisfy my needs if I ever wanted that e-bike. US$8,600? Oh. If I had this money and wanted a SUV e-bike then I would rather look at an R&M

 

[kevinmccune]

power ratings are torque over time,you can have something with a lot of torque and very little absolute power like a starter motor,you can have torque that shatters axles that has very little top speed,in low gears my ebike with me pedaling has enough "torque to pull up a steep incline,oth hand if it had enough power our torque curve would stay flat and not fall off and the speed( torque over time) would let me fly up that hill,absolute ability to do work(watts) is always dependent on power input among other things, the more force you can generate the more you can move if you have enough capacity to do work you can move it fast,trading power input for speed energy is conserved,the electrical energy is converted to mechanical energy(if there is such a thing) converted to force of motion(kinetic) with all attendent losses along the way,you can see this on a dynometer,the torgue rise will level off with hp increasing with speed,i can move a hundred ton railroad car with a "gandybar",i just cannot move it fast at all

 

[AvalancheRun]

Torque without the rotational speed simply means nothing It is the max mechanical motor power that counts. The published figure for the CYRO Drive II is 35 Nm at 670W. The reference rotational speed of the rear wheel is then 670/35 = 19.14 rad/s or 183 rpm.
-----------------
It's the theory. If we, however, check what the 183 rpm actually means for the wheel size expected from Stromer ST1, it would only mean around 23 km/h e-bike speed, which you know is far higher in real life! Something stinks here. I would then drop the "torque" reasoning completely and just concentrate on the specified max motor power.
-----------------
Stromer does not explain whether the published 670 W is the electrical or mechanical power. If that's the mechanical power, ST1 is a powerful e-bike. If that's the electrical power, the actual max mechanical motor power would be around 520 W, which is the same as your 85 Nm mid-drive motor.
-----------------
Your experience was a high acceleration rate on the flat. Correct. Stromer ST1 motor is a Direct Drive (not internally geared), which has the full torque at zero speed. DD motors love spinning fast and achieve the high efficiency at the high e-bike speed. However, the same feature makes them hopeless climbers. The reason being your e-bike speed would drop dramatically on a steep climb; as the motor rotates at the rear wheel speed, the motor would get into the slow spinning rate, making it highly inefficient, and releasing a lot of heat. That is a know phenomenon, leading to overheating or sometimes melting the motor (if the thermal protection is inadequate).
-----------------

I was reluctant to mention speed, but it climbed hills similarly to my 75 nm Bosch. I have heard that they will reduce power after long periods of climbing.

I have configured a version of ST1 that would satisfy my needs if I ever wanted that e-bike. US$8,600?

Unused 2023 models go for just $2k USD on Upway. I'm tempted to just roll the dice.

Oh. If I had this money and wanted a SUV e-bike then I would rather look at an R&M

I agree and would be riding an R&M right now if they had a quiet motor. Speed and CX are so annoying to me. Performance Line 75 nm is fine, Specialized Brose 90 nm motor is fine, the Stromer is 5x quieter than those, virtually inaudible.

Thanks for the info!

 

[Stefan Mikes]

I forgot to mention the nature of the power delivery for hub drives and mid drives is totally different. As you know, a mid drive rewards your pedalling effort, as the assisting motor power is variable (depending on how hard you press the pedals with your feet and how fast you are spinning the crank). A throttless hub drive delivers a constant power to the rear wheel per assistance level, and your crank only serves as the switch to turn the assistance on. This makes the performance of the e-bike very little dependent on your own power input. It is like getting a very strong tailwind and just pedalling to achieve the force equilibrium.

That feature of hub drives makes them excellent commuter e-bikes, as the hub drive e-bike will always tend to achieve a constant max equilibrium speed per assistance level and keep it. It is, however, hard to ride a hub drive very slowly when needed. Additional nice feature of DD drives is high torque at cold starts.

With mid drives, the "tailwind experience" is replaced with "Uh-oh, I'm a Superman!" I'd say hub drives are very good for commuting while mid drives are ideal for recreation and fitness. Mid drives are perfect climbers, too. Now you might understand why I do not ride my hub-drive motor e-bike anymore even if I still own it

 

[AvalancheRun]

I forgot to mention the nature of the power delivery for hub drives and mid drives is totally different. As you know, a mid drive rewards your pedalling effort, as the assisting motor power is variable (depending on how hard you press the pedals with your feet and how fast you are spinning the crank). A throttless hub drive delivers a constant power to the rear wheel per assistance level, and your crank only serves as the switch to turn the assistance on. This makes the performance of the e-bike very little dependent on your own power input. It is like getting a very strong tailwind and just pedalling to achieve the force equilibrium.

That feature of hub drives makes them excellent commuter e-bikes, as the hub drive e-bike will always tend to achieve a constant max equilibrium speed per assistance level and keep it. It is, however, hard to ride a hub drive very slowly when needed. Additional nice feature of DD drives is high torque at cold starts.

With mid drives, the "tailwind experience" is replaced with "Uh-oh, I'm a Superman!" I'd say hub drives are very good for commuting while mid drives are ideal for recreation and fitness. Mid drives are perfect climbers, too. Now you might understand why I do not ride my hub-drive motor e-bike anymore even if I still own it

More fantastic info, I really appreciate and can related to the way you're describing the motor differences. Choose your experience: Never-ending tailwind, or Superman. Actually this is what drew me to a Bosch powered bike over the Specialized Vado to begin with; it felt more like a tailwind in Turbo mode than the Vado. Kinda nice to have that duality, but the naturalness of the Brose is unmatched in my subjective opinion.

Personally, I love the feeling of a great mid-drive.

The other thing I didn't quite love about the Stromer was the surge after pedaling. Perhaps it was the model (a 2022 ST3), but it was similar to riding other hub drives. Very minor nit though. The Stromers ride unlike any other bicycles. They are so planted, smooth, silent, and virtually vibration-free.

Have you ridden a Stromer?

 

[Stefan Mikes]

Have you ridden a Stromer?

Not.
When I was buying e-bikes one after another, Stromers were unavailable in Poland. Even today, there are no serious (read: big and close enough) Stromer dealers where I live. If they were... I would not be interested in e-bikes as proprietary in their design as Specialized would not even dream to make them in its worst nightmare I would not be interested in the Direct Drive either. (Just think of removing the rear wheel with an extremely heavy motor for tyre field repair!) And well, any e-bike needs an LBS that is close to you and you can trust the LBS.

In my early naievety, I was fancying an R&M e-bike (could afford it as a single e-bike to own at that time). Fortunately for me, R&M treats East Europe as The Wild East and does not sell its e-bikes outside several richest countries of West Europe, US/Canada or AUS/NZ. The brand has no serious representation in Poland, either.

My needs are precisely defined. Let me just tell you my low-cost Lovelec Diadem (a Czech hub drive e-bike) is inexpensive in maintenance, is a regular "traditional" e-bike, and easily gets me at 20 mph whenever I need