Why Do e-Bikes Need Derailleurs and Gears?

They literally only ever use 2 or 3. I've seen so many cassettes with a couple of totally worn sprockets and the rest have never seen the chain. The fact that shimano now sell the bottom cluster separately says a lot tbh.

This is an interesting point for discussion. I don't see why anyone should "hate" it but I guess it takes all sorts. What follows contains large amounts of speculation...

Electric vehicles can survive with one or two gears because their motors have mountains of torque, beginning from 0 RPM, and don't have a narrow operation band like internal combustion engines do. In the case of most consumer EVs, the one (or two) gears are easily enough to operate from 0 km/h to the speed limit. There are exceptions - electric race cars still have more gears because of the wider operating range, but they do still have many fewer gears than "traditional" ICE-powered race cars (do we call them acoustic cars?... )

EVs are already very heavy by virtue of their battery systems so their motors can be as big and heavy as they need to be without affecting overall system mass and packaging too severely. Electric bicycle motors (and battery systems) on the other hand are much more constrained in size and mass, while their performance is constrained by legislation. The bikes themselves are still putting out only about as much power as a reasonably fit recreational rider.

However, there already are pedal assist e-bikes with large enough motors not to require multiple gears, Stealth being just one example.

I'll bet my left ball Shimano have some sort of drive/gearbox in one unit under prototype somewhere, this isn't just for E-mtb, but commuter, touring, road etc it just makes so much sense to use.

why do they have gears, well as you know they assist the rider, they don't propel the bike without input from the rider.

The mechanical advantage gears give allow the rider to pedal at a cadence and effort that will "simulate" riding a normal bike.

You could have a single speed for sure, but the effeciency of the system would take a huge fall, your range might go from 60km down to 20km depending on elevation.

Now this is the tricky bit, where do you draw the line at what is a e-mtb and what is a full blown motorcycle? A lot of you will say "as soon as it has a motor it's a moped" etc, but I think it's more complicated than that.

"bikes" like the sur ron or whatever it is are basically a electric trail bike, use a throttle or thumb switch and require no input via pedals to move with assistance, the batteries are huge and they weigh a shit load.... this isn't e-mtb to me.

TLDR; I use all 10-51T on my E-mtb, dont @ me.

Hater here... Why Do e-Bikes Need Derailleurs and Gears? Because without them we are one step closer to electric motorcycles on multi-use trails. At least having gears is enough to confuse some of the idiots enough to keep them out. I was going to keep my Hater mouth shut until I was just at a diner and saw a noticeably unfit family ride by and then rocket up and over an overpass while "Pushing." the pedals at a cruising pace. E-bikes have regulated levels of assistance and gears help to delineate them from electric motorcycles which are not welcome on multi use trails.

Don’t most electric vehicles have CVT transmissions? So they have gears it’s just an infinitely adjustable range from x to y. If they had no gears, just direct power, the batteries would be drained super fast. I’m no expert, could be way off.

Electric motors don't have peaky torque, power and efficiency curves in the way ICE engines do. A properly implemented CVT is used in ICE applications to keep the engine operating around one of these peaks.

And without an external load, an electric motor basically only needs enough energy input to overcome bearing drag, regardless of output shaft speed (within reason, of course). Essentially, energy input is proportional to load.

@thejake sorry, you're way off. There is a transfer case involved in the majority of cases (because tyre rpm range != motor rpm range, so you just shift it around a bit with a gear pair), but other than that, no gears (well, except the Rimac One and the Porsche Taycan/Audi e-Tron GT platform).

@sspomer pedal power being the throttle means you do not have a mechanical connection (well, is an electromagnetic connection a mechanical connection or not? Let's not dive into that one I guess ) between the pedals and the rear wheel. In that case you'd be pedalling at a constant rpm and the bike would accelerate. That would make the bike have a sort of an electric CVT.

The issue is that in that case you have a pedal operated throttle switch (if for example 90 rpm on the pedals is 'zero', more than 90 rpm means accelerate, less than 90 rpm means slow down) with basically no energy added to the system. That would make it a motorcycle with the throttle on the pedals (as mentioned) instead of on the handlebars.
It would be possible to add a generator to the pedal spindle to add (electric) energy via the pedals, so the pedals would resist turning and the rider would have to exert the same amount of energy as they have to now. That would mean the generated electricity would power the main drive motor, where the battery would add the energy that a normal e-bike system adds for the final total output. In that case you quite literally have an electric drivetrain a-la diesel electric locomotives, series-hybrid and range extender cars, all cases where an ICE engine at a set load and speed (most efficient working point) generates electricity via a generator, which is used to power the vehicle via electric motors at varying speeds and loads - literally an electric CVT.

Without doing any calculations about efficiency, weight and, most importantly, cost, I'd hazard a guess slapping a standard drivetrain on a bike makes it cheaper, lighter, more efficient and closer to a classic bike, which will make buyers more likely to buy a bike like that.



So, TL;DR, e-bikes have gears because people aren't able to pedal across a wide range of rpms and thus need some sort of gearing involved to be able to reach both 5 kph (uphills) and 30 kph (flat/downhill).

As for Teslas and single gears, yeah, electric motors have a wide range of use, but they still have their optimum point with the highest efficiency. Case in point, Tesla dual motor cars - the two motors are optimized for different speeds and one is turned off with only the other one working at highway speeds. They used to use AC/induction motors, so they could just turn it off, but Taycan/e-Tron GT use permament magnet rotors if I'm not mistaken, where you can't just turn them off (rotating magnets induce current in the winding and thus have quite a bit of drag whereas an induction motor does not). I'm assuming a lot here, but I think they used a clutch in the rear to be able to turn the rear motor off for highway speeds (Taycans are FWD on highways for efficiency reasons). Since they had a clutch in there, they maybe added a second gear to help with accelerations as well.

Because Big Derailleur is afraid of gearboxes and wants to do everything to avoid admitting they're better...

Realistically, with batteries already on the bike, an electronic-shifting gearbox would make an awful lot of sense.

I wouldn't want that system on my bike, but I do want a gearbox. I see e-bikes as a good market for gearboxes, ESPECIALLY for commuting e-bikes and cargo bikes

Like I previously said, it's beyond me why Pinion positioned themselves into the commuting e-bike market with a rear hub motor only and didn't go for a motor integration into their gearbox. Their solution already requires a custom frame without a BB and a manufacturer would only need to implement the battery into the frame besides the gearbox (and supposed motor). Plus they took care of the pedals to output gear connection (disconnection), they would just connect the motor to the output shaft.

It's a no brainer if you ask me... Complete win-win.

Primoz said it well: "So, TL;DR, e-bikes have gears because people aren't able to pedal across a wide range of rpms and thus need some sort of gearing involved to be able to reach both 5 kph (uphills) and 30 kph (flat/downhill)."

Could riders get used to low rpm but highish human effort on climbs? Maybe, it'd be easier than single speeding, and people do that. But another aspect is that ebikes (highend emtbs) are mostly being marketed to and bought by mountain bikers, so having gears, the same gear range as an mtb (even if it makes less sense on an emtb) is partly a familiarity thing. But I've never ridden an ebike, I've got dirt bikes if I'm in the mood to go fast.

Looking at the average ebiker, they don't know what gears are. Personally I couldn't do singlespeed or low cadences...

'literally only ever...' is pretty bold considering I use all gears? Why would I not when I do fast steep downhill then steep climbs back up?

Totally, this makes no sense.

In France, Effigear is working with Valeo to develop an automatic gearbox/motor system. It's aimed mainly at commuting and seems like a logical way forward. See the other site for more info in english.

You clearly haven't seen people doing mid-cassette-steep climbs (when not electric powered) in the hardest gear at ~30 rpm on an e-bike, have you?

While not a shop rat, I can confirm there are tons of people doing 30 rpm and not using gears on e-bikes. The wonders it does on their drivetrains...