Hub Motor Vs Mid-drive comparison

Ravi Kempaiah

Well-Known Member
My friend, Adam has put together this awesome, scientific video comparison between his two drive systems.

Few months ago, he published this excellent article about commuting on E-bikes and cheating.

There is an existing notion that mid-drives are better hill climbers. That's true with a caveat. It's only in slow, technical off-road conditions, mid-drives help you with extra torque but on road and paved surfaces, hub motors win hands down.

A well tuned hub motor is easy on the drive parts and is reliable. ST2 has controller in the downtube unlike ST1, which eliminates controller failure and helps heat dissipation.

Look at the stats. Great video.
Also, people who were quoting Torque numbers like 90Nm, 80Nm Vs ST2's 35Nm, I welcome your dissenting voice.

 

Ravi Kempaiah

Well-Known Member
Rider watts were 418! Lowest rider watts were 250w. Not really the profile of the average ebiker around here, who is in his/her 60's. More typical would be 100 watts.

I think it is human + machine combined. To keep the baseline constant, he did climb the hill few different times and documented the watts.
I know he can easily maintain 250 watts over long distances.
 

TenBlinkers

Member
How do you calculate human watts vs machine watts? If I'm looking at the display on my bike and it says 250w, is that combined or just the bike motor?
 

Ravi Kempaiah

Well-Known Member
How do you calculate human watts vs machine watts? If I'm looking at the display on my bike and it says 250w, is that combined or just the bike motor?

Some of the GPS systems does it for you. They take into account the location gradient, key bicycle parameters, bicycle speed and calculate the Watts needed to move at that speed.
Machine watts is extremely dynamic and it dictated by the controller output, which in turn is dictated by your pedal torque. The same for human watts. What is being displayed on the screen is total input from human+machine combo.

Unless you have a Watt meter at the location of the motor, it will be hard to measure the dynamic machine watts. Some manufacturers include a small moving bar on the display to indicate this dynamic response.

With all fairness, I should include something about mid-drives. Let's say, you have a steep hill and you're starting from dead stop without any momentum. That's when hub motors struggle.
Here is a neat video of Haibike doing something most hub motors wouldn't be able to. However, this is a rare scenario.

 

flymeaway

Well-Known Member
I welcome your dissenting voice

Different watt rating? Different input voltage? How was this comparable? I have two virtually identical BBS02 installations. Very similar bikes, but one is 750W @ 48V and the other is 500W @ 36V. I have ridden both bikes over 2,000 miles on my work commute and I assure you there is no comparison, the 750W - 48V set-up is much more powerful. The only point made on the video I found useful was the comment about shifting the mid-drive on the hill, that is certainly a disadvantage.

He should find a 500W , 48V mid-drive and repeat....

Court J.
 

Tara D.

Active Member
Adam made an awesome video! Thanks for sharing it here @Ravi Kempaiah. I think a lot of people will find the visual helpful when trying to decide what is best for them. Even if they are only going to be putting out 100 watts.
 

George S.

Well-Known Member
I was working back through the numbers a bit, knowing that Adam rides hard and the total watts include the motor. He's just not working the motor very hard, in either instance. I don't know what would happen if you just took the two motors and put them on a throttle, ran them both at 700 watts, something around the legal limit. It's kind of tough to say what the pedal assist is doing, and at the end, with similar watts, they were going about the same speed.

It's great you can show all this data, though it's also a little confusing. Eventually you'd like to be able to tell people the real performance characteristics of their motor, maybe with their 'standard' amount of rider assist. How immune is one hub motor to bogging down, generating heat, versus another. Lots of stuff you could do with the video capability.
 

opimax

Well-Known Member
I would note that they are comparable as prebuilt ebikes at the higher end of costs.

Also from short test drives of a couple mid drives, at the bottom of a steep hill going from a dead stop I would think it would be a different outcome
 

Reseg

Member
Hey guys, glad you liked it! The 418W was just my power. Both bikes had their assist maxed and motor assist reading max the whole time (except the Focus shifting). I did much more than that, I took temp readings and documented it all with pics but I completely destroyed my phone by accident the next day, before I got the stuff off of it.

The test WAS from a stop at the bottom of a hill. The point I was starting from was 8.3% grade. It looks like it goes up from there, because it does, it hits 17%. The top, where I stopped was almost flat.

I'm not saying it's 100% conclusive, as I would want to do it with multiple bikes and power meters to consider it a study. As for why these 2 bikes are comparable, they're both long-range ebike options many people in the market consider both of. The Stromer is 48V 500W, but the Focus is rated at 70Nm, is lighter, and many say the mid drive is better on a climb over-all. I wasn't going out to prove anything, I honestly thought the Focus would win. However, if I had more time I would have tested the potential over-heating. I suspect the Stromer was reaching its limit after doing multiple back to back climbs, then using regen to go down, I didn't give it a break. The Focus was probably fine for many more climbs, well, until it stripped the plastic gear, uggg, I'm on my 3rd motor now.

I plan to do some actual motor output (pwr/torque) of both motors, as it relates to input power, as well as at different battery levels. It's just a matter of having the time since I'm so busy at work.
 

Reseg

Member
I got over 2k miles on the motor it came with, the replacement didn't make it 1k miles and they did the same thing when they went out. When the 2nd one went, I sent an email, but only gave it a couple of days and really needed my bike. I still had the 1st motor, so I took t apart to see if I could fix it instead of having to get a whole new motor. I was hoping maybe a pinion gear just needed tightened to a shaft or something. The motor sounded fine but was free spinning.

When I opened it, I found this stripped plastic gear in the attached pic. I wonder if this was the new technology that went into the new impulse motor to make it "quiet". So I tried to see if I could order a half dozen of them to have if I needed, or get the specs to get them made. Focus was only willing to replace the whole motor again (I felt bad, seemed like such a waste to replace a whole motor unit for a plastic gear), but they wanted to pay to send the bike to an authorized location, so I had to do that. While waiting, I bought an ST2 and I'm glad I did because the Focus took 2 months from fail to fix.

I really don't mean to bash Focus. I loved the bike, I rode it hard, and had a lot of fun. I suspect people who don't ride as extreme as me (40+mile daily commute on max assist in Austin heat, hammering it hard and keeping the motor running all-out) will never have a problem like this. But the ST2 is just a whole different experience. I don't want to write as if I have final thoughts on the 2 compared, because the ST2 has yet to face an Austin summer with me.

I've met a lot of great people related to these purchases and needs. Crazy Lenny and Stromer reps, and Propel Bikes, as well as the Focus reps who have been trying to help and not just dump me off as not worth it if I'm going to rip through motors every few months.
 

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flymeaway

Well-Known Member
When I opened it, I found this stripped plastic gear in the attached pic.

Wow...yeah that's ugly. Frankly I'm baffled when I read about (and see pictures) of stripped composite gears. If I were the manufacturer I'd be eating piles of humble pie. What I really find strange about the problem is that high quality engineered plastics are being used, and have been used for years, in much more demanding motor/gear reducer applications. For the sake of good PR and reputation (never mind the cost and inconvenience) they should use the appropriate materials and manufacturing techniques. I would have assumed by now that the manufacturers would have realized the need for a better design/material.

Thanks for the video, great job!

Court J.
 

flymeaway

Well-Known Member
But the ST2 is just a whole different experience. I don't want to write as if I have final thoughts on the 2 compared, because the ST2 has yet to face an Austin summer with me.

Having only been engaged in EBiking for 2 1/2 years I'm still learning. I think peoples choice of what bike works best is experience and personal preference, I don't think there are right or wrong, better or worse. If the market for Ebikes continues to grow I believe we'll see better technology in every facet and more competitive bikes.

Bottom line...have a blast while saving time, money, energy and staying fit!

Court J.
 

Reseg

Member
$2,000, haha. Guesses are cheaper!

hahah yeah the power meter pedals aren't cheap, around $1100 USD. The best option, if you wanted to monitor your own power, in regards to bang for the buck, with good quality/accuracy, would probably be the Stages crank arm.

I believe the ST2 uses FSA BB30 175mm, so you could get this one:
https://store.stagescycling.com/stages-power-meter--energy-bb30-p851.aspx

$530 USD, but that's MSRP, so you can probably find it cheaper.
You would just pull off your left crank arm and put this on.

The benefit to the pedals is they're easy to swap from bike to bike, and they read individual leg power. So I see my left vs right leg output, which my left is stronger. The one sided units re most common and they just double the power, basically. I only really justified it because, well, I'm data-obsessed, and my work involves collecting muscle oxygen data on different muscles and it's nice to isolate each leg to the muscle oxygen in that quad/calf.

Or, another option, if you've building up miles and need to change your chainrings due to wear, you could spend a few hundred more for this:
https://www.powertap.com/product/powertap-c1-chainrings
It's supposed to be compatible with FSA Gossamer (on my ST2). You'd get the 52/36 version, to keep the gears the same as stock. (it's ~$600 shipped).

I'm not saying everyone needs a power meter, but they can be useful in monitoring your output, and are used with many programs, like Training Peaks, Golden Cheetah, and even Strava, to calculate your ride intensity, fatigue levels, fitness levels, and recovery needed.