As far as I’m concerned, torque-sensing’s existence is primarily owed not to the fact that it is a better system, but instead is a tool to help persuade an existing customer base (recreational, leg-powered cyclists) not to hate the product (ebikes) quite as much as they already do (either that or to sell ebikes while not cannibalizing sales of analog bicycle brethren).
What is Torque-Sensing Pedal Assist?
On an ebike, when a torque sensor is used, it applies a strain gauge to the drivetrain (located either inside the bottom bracket, or in the back of the bike near the gear cluster). This measures the amount of force you apply to your pedaling stroke. If you pedal (work) harder, the assist you receive is dialed up. If you pedal more softly – regardless of your cadence – the assist level is reduced… or eliminated.
I have heard it said that torque-sensing “rewards pedal effort” and this statement is both correct and indicative of the root problem with its advocacy. Old school cyclists hate Hate HATE the fact ebikes allow someone to make forward progress without using their muscles in the first place. By restricting/keying the assist to physical exertion levels, the fact that a motor exists at all is less difficult to accept – and more easily sold to the existing cyclist population.
It also allows an ebike to be sold without denigrating the old-school unassisted version. Zillions of which are still manufactured for sale worldwide. If torque sensing just makes it seem “more like a regular bicycle” then that helps preserve the perception that a normal bicycle is still every bit the desirable, viable product that manufacturers still need to sell millions of.
It is unfair to say torque-sensing is ONLY about these things. Its not. You will also hear people say torque-sensing results in the most ‘natural’ bicycle riding experience for them, since you still have to work hard on the pedals. And the assist increases in proportion to your effort, just like a real bicycle. An ebike goes faster of course, but a physical work ethic is still demanded. So to be fair, torque-sensing does indeed give cyclists who want this a familiar and desirable experience. There is nothing wrong with that.
What is Cadence-Based Pedal Assist?
In its simplest form, its nothing more than this: Your assist level goes up or down based on how fast the crankarms are turning. The amount of effort you expend could even be irrelevant if your gearing is low enough. The only thing that matters is the rotational speed of the pedals/crankarms (strictly speaking it is the spindle’s rotational speed that is measured, but thinking ‘pedal rotation’ is easier to visualize).
So if you want more assist, you just turn your legs faster – not harder. Again in simple circumstances this means you can get into a low gear and easily ‘ghost pedal’ your ebike, without expending any effort. So you are breezing right along right up to either the speed limit of the ebike or the road/path you are riding on.
Such a thing is utterly anathema; deeply, personally hated in the cycling community. There, your progress and ability is hard earned through what can only be described as prolonged, personal, stoic suffering whose level outsiders neither understand nor hope to match. Despite the spandex, funny hats and silly shoes, cyclists know they are endurance badasses (they really are).
Except, fate has dictated these solitary warriors suddenly have to share the road with the Griswolds, blowing past them in their two-wheel Trucksters. Ebikes democratize cycling so that now… anyone can do it? WTF!?!
… not a shock the response of cyclists to ebikes has been negative.
Its not so simple
I said above the description of cadence-based pedal assist was in “its simplest form”. There are some cadence-sensing ebike motors that have settings both complex and rather profound in how they impact the riding experience. Notice I did not say ‘cycling experience’ because a central tenet of my rejection of torque-sensing is that ebikes are not bicycles. It is a mistake to treat them as if they should behave the same (unless that is something you expressly want).
UPDATE: Since this article was written in 2019, I have documented all of the settings in BBSHD Programming for the Pedaling Cyclist.
Torque-Sensing Can Be A Disaster
If you have a physical limitation, torque-sensing doesn’t help you get past it. It does help you go faster while working hard. Studies have shown that ebikers in fact can work nearly as hard as, or even harder than bicycle riders… they just don’t realize it. Possibly this is due in part to the exhilaration of being able to go faster, and stay in the saddle for longer periods.
Myself, I am a lifelong cyclist. Or rather, I was. I commuted daily for decades. For many years I eschewed the use of an auto. I commuted and even shopped for groceries by bike (being poor and single had nothing to do with this of course). But after a couple of heart attacks, my cycling life was over. To stay alive, I gave up the intensely personal activity I most valued. Bummer.
A few years ago, I discovered ebikes, and the one I bought had cadence-based assist. I had no idea there was another kind of system at the time. I did something many old-schoolers do not: I treated the ebike – which looks like a bicycle but is not one – as a new animal. I threw out much of of the knowledge on cycling I had acquired, and started over on riding technique.
At the start, pedal effort very quickly led to chest pain and an immediate need to stop doing that. But I could go on if I incremented up the assist and incrementally lowered my pedal effort. This allowed me to keep going (maintain forward progress).
I learned to treat the ebike like an exercise machine. An exercise machine that went places and was practical transportation. Instead of directly coordinating effort with forward motion, I separated the two. Effort was always maintained, and so was clicking off the needed mileage to my destination. But the two no longer had a 1:1 relationship. This decoupling of effort vs. speed solved everything. The procedure in a nutshell is as follows:
- Set a preferred cadence
- As heart pain occurs (heart pain /= being tired) click up the assist level so I get closer to or completely ghost pedal the bike – and keep moving
- On recovery – I’m good after maybe a half block – ramp down the assist level a click at a time and start working harder again
- All the while maintain the same cadence
- Rinse and repeat as the miles click off to destination arrival.
Again, to belabor the point: This is transportation. My bike has somewhere to go, so the point of cycling is to reach a destination. If I was a recreational cyclist then maybe its fine to stop and sit on a bench for awhile. But the point of riding for me is to get somewhere. So I must maintain forward progress while managing my exertion level.
Only cadence sensing is going to let you do that (and I know this from experience. See Afterword below). Its a different riding experience described most simply as an exercise machine that is moving. Again… not a bicycle.
Different But Still Good For You
Over time and thru repetition, I scaled back the point where pain occurs to where I was able to change my bike’s gearing. Now I’m running at top assist speed while maintaining pedal pressure and exertion at all times during the ride. On my Class 3 daily driver I cruise right at 28-30 mph (legal in my jurisdiction) and I get to those higher speeds above the assist limit by myself. All along doing so by maintaining a set, preferred cadence.
And if I overdo it, since I am now running this auto substitute at full power, I can just upshift (maintaining cadence on the easier gear) to take a break while only losing a mph or three. This is a different way to use cadence-assist. I am not dialing back power: I’m always running at full blast. Instead I am just varying my pedal effort up and down via gear changes.
What happens to a rider with physical restrictions who tries to depend on a torque-sensing ebike for transport? You ride, you need a break, you want the bike to help and… the bike tells you to fuck off. Unless you work hard enough to deserve a reward, it refuses. So much for dependable transportation.
Broadening The Use-Case
Cadence sensing isn’t just for recovering invalids. For the healthy rider, successful use of cadence-based assist as a hard-exercise tool is easily possible, and rooted in that rider not coming into the experience with pre-conceived ideas. Don’t treat it like a bicycle (yes I am repeating this over and over on purpose).
Using the ebike as an exercise machine as you roll down the road, you’ll be getting fit during time otherwise spent sitting in your car and exercising nothing. A torque-sensing ebike can do this too… but if the ebike is meant to also be practical transportation, your physical condition of the moment will have a direct impact on whether you make it to your destination. Not so with cadence assist.
It took 34 years for the Tour de France to allow bicycles with derailleurs — because not grinding up a slope in the Alps on a single-speed was cheating.
… Isn’t it better to triumph by the strength of your muscles than by the artifice of a derailleur? We are getting soft.
-Henri DesGrange, world-renowned cyclist and original TDF organizer
If someone tried to make that same case today, their opinion would be regarded as fringe idiocy.
So lets take that same interval: 34 years from now, when ebikes have long-since become the accepted norm (just look at the sales figures) as derailleurs did a century ago… will we be espousing technology or methods rooted to the norms of the past? Will a couple of generations of riders who have known nothing else continue to think of torque-sensing assist as giving a bike a ‘normal’ feel?
My money is on ‘no’. Or more accurately… sorta-kinda-no. I think for higher end bikes a dual system could become commonplace, letting riders choose one or the other as they see fit in the moment. One mode for recreation. One for transportation.
If it has to be a this-or-that binary choice, I think torque-sensing won’t survive the test of time. Why? Sheer weight of numbers, and the growth of the automobile replacement market. Look at global ebike sales. Only a small fraction of ebikes are sold in the European and North American markets, where recreational cycling is a thing. Look at the Far East, where bicycles are simply utilitarian transportation and there is no stigma attached to effortless travel. Whats the norm there?
UPDATE (February 2021): Its already happening through a vector I hadn’t considered. Recreational ebike riders are starting to upgrade from their cadence-based budget bikes to what the industry tells them was the ideal product: a better bike with higher end components and… torque sensing. I’m seeing reviews from riders not inculcated in traditional cycling ethos, saying the bikes are no longer fun. They can’t just get on a bike and zip around and enjoy the outdoors for as long as the battery holds out… now their bike is making them work at it. What was once an unconsciously-achieved benefit (exercise) is now an enforced requirement. Riders like this, new to the fold, don’t always appreciate the new rules. With the pandemic rushing literally tens of millions of new riders into the fold, the spread of this effect could manifest itself far more quickly than the slow evolution I originally anticipated.
Lest I give the wrong impression… I have an ebike that uses torque sensing, and frankly I love it. But its a recreational bike, not suited for a bike that has a job. Going for a fun ride, where I don’t have a problem stopping and sitting down on a bench or a rock for awhile and enjoying my surroundings… Its almost perfect for that. I wish I had time to ride it more.
But by its nature it can’t be a serious transportation tool.
3 thoughts on “I Hate Ebike Torque-Sensing (maybe you should too)”
I think the primary benefit to torque sensing is the extended range.
Many bikes are geared in such a way that at higher speeds you’re ghost pedaling at any speed.
My personal taste (rules not withstanding) would be a throttle + torque sensing.
Ghost pedaling can be eliminated in a couple of ways. First and foremost, on a hub drive, with a KT controller, those controllers do not treat PAS as an on/off proposition at all. Low speed and rpms are accounted for directly and assist is adjusted (assist decreased) when cadence and speed increase. It never happens on a BBSxx that has been tuned properly, but you would never think that if you have only experienced the appalling factory stock settings. I wrote an article addressing that issue specifically. https://talesontwowheels.com/2021/01/18/bbshd_settings_programming/
I think the ideal, finally being realized, is the combination torque+cadence sensing which you see on the Cyc motors, the most refined of which is on the new Photon.