# Why do eBikes need gears?



## derkommissar (Jan 23, 2019)

I was just thinking Teslas don’t have transmissions. If the point of adding a motor to a bicycle is to augment the rider‘s power why is there a need for gears at all? Couldn’t the motor provide all the assistance needed for climbing hills or going fast on flats?


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## eb1888 (Jan 27, 2012)

Absolutely . . . .until the battery runs down.
Then you could pedal up hills or walk a single speed version.


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## Cleared2land (Aug 31, 2012)

Pedal assist?


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## RBoardman (Dec 27, 2014)

Clearly you’ve never ridden one of you think they don’t need gears. I have 52t Eagle and use every bit of it on my ebike.


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## underblu (Aug 24, 2021)

derkommissar said:


> I was just thinking Teslas don't have transmissions. If the point of adding a motor to a bicycle is to augment the rider's power why is there a need for gears at all? Couldn't the motor provide all the assistance needed for climbing hills or going fast on flats?


I use the first 4 gears regularly as I keep the bike in eco mode for minimal assistance. In trail mode I could power up any elevation with only the first 2 gears. However for steep uphill climbs even in boost or turbo mode, gears will still be necessary even with pedal assist.

Now at some point gearing will likely become integrated with the motor eliminating the traditional drivetrains but gearing itself on an ebike will still be necessary.


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## .WestCoastHucker. (Jan 14, 2004)

when my ebike has the power of a Tesla, maybe then it won't need gears...


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## derkommissar (Jan 23, 2019)

Yes you are right. I‘ve never ridden an ebike but there are larger and heavier EV’s that do without a transmission. So you think it’s not currently possible to scale down a strong enough motor & battery to replace gears on a bicycle? However, we do examples of smaller electric vehicles that don’t have a gear boxes like scooters and skateboard boards.


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## ctrailbiker (Aug 19, 2021)

derkommissar said:


> Yes you are right. I've never ridden an ebike but there are larger and heavier EV's that do without a transmission. So you think it's not currently possible to scale down a strong enough motor & battery to replace gears on a bicycle? However, we do examples of smaller electric vehicles that don't have a gear boxes like scooters and skateboard boards.


A motor that powerful would probably change the ebike's classification and be illegal on many trails that currently allow ebikes. With that much power an ebike would actually do the kind of damage to trails that many early on feared. Such as peeling out in the dirt etc. You would also need some sort of mechanism like gearing for the rider who needs to be able to pedal at a comfortable cadence.

Tesla's for example have very powerful motors in them and don't have a transmission, Chevy volts on the other hand have weaker motors and have a CVT transmission in them.


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## derkommissar (Jan 23, 2019)

Also a side thought what means does an electric motor have manage torque and speed the way a mechanical motor does through a gear box?


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## Loll (May 2, 2006)

On my first ebike demo, thats what i did. Using only the three modes to go up anything. Then I realized the cadence is not right, or I would spin out. The gear fine tuned the assistance.

Also, some ride in eco mode to mimic a normal bike for the workout, then increase the assistance when they are tired.


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## acedeuce802 (Jun 30, 2017)

derkommissar said:


> Also a side thought what means does an electric motor have manage torque and speed the way a mechanical motor does through a gear box?


What do you mean by a mechanical motor? Not really sure what you're asking.

To answer the original question, a Telsa doesn't need a gearbox because electric motors have a very wide torque curve. Ebikes have gearbox/drivetrains because they are only assisting torque from human power, and humans are only efficient between a narrow RPM band, say 70-110 RPM.


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## chiefsilverback (Dec 20, 2019)

derkommissar said:


> Also a side thought what means does an electric motor have manage torque and speed the way a mechanical motor does through a gear box?


A Tesla's motor(s) delivers 100% torque 100% of the time which is why they accelerate so ridiculously fast. The control system is controlling the RPM and how quickly that increases, think of it like a power drill, it always turns with the same force (torque) you just control the speed with the trigger.


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## acedeuce802 (Jun 30, 2017)

chiefsilverback said:


> A Tesla's motor(s) delivers 100% torque 100% of the time which is why they accelerate so ridiculously fast. The control system is controlling the RPM and how quickly that increases, think of it like a power drill, it always turns with the same force (torque) you just control the speed with the trigger.


Yeah that's not true at all. If you push 5% throttle on a Tesla to go 25mph, it doesn't take off like a rocket ship than stop accelerating at 25mph. Similarly, if you try to remove a bolt with a drill or impact driver by pushing the trigger 5%, it will not untorque the bolt. Tesla's have the ability to accelerate so ridiculously fast because electric motors have the ability to produce near full torque from zero RPM, but they'll only do so when the motor controller commands full current.

Torque and speed are tied together and are controlled through a motor controller, torque is generally relative to current and speed is generally relative to voltage. The controller will handle both to give the amount of current and voltage needed to satisfy the command. As torque increases, speed increases (until forces at equilibrium) because F=ma.


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## 127.0.0.1 (Nov 19, 2013)

derkommissar said:


> Also a side thought what means does an electric motor have manage torque and speed the way a mechanical motor does through a gear box?


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## RBoardman (Dec 27, 2014)

derkommissar said:


> Yes you are right. I've never ridden an ebike but there are larger and heavier EV's that do without a transmission. So you think it's not currently possible to scale down a strong enough motor & battery to replace gears on a bicycle? However, we do examples of smaller electric vehicles that don't have a gear boxes like scooters and skateboard boards.


Not without drastically reducing the ebike range. I use all my gears so I'm always climbing at the most efficient cadence and my power input is consistent. Even two people on identical bikes going the same speed can have large range differences just based off of pedaling habits and always being in the "right" gear.

I hope we get to a point where battery technology can be significantly smaller and lighter with greater capacity so range is not an issue, and I don't have to ride all day in eco trying to save every last juice of power.


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## Zguitar71 (Nov 8, 2020)

A Tesla motor can also spin at thousands of rpm, your legs cannot. If you want a single speed pedal assist, picking the right gear is going to be pretty hard.


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## wolfmw (Dec 18, 2020)

acedeuce802 said:


> Tesla's have the ability to accelerate so ridiculously fast because *electric motors have the ability to produce near full torque from zero RPM*, but they'll only do so when the motor controller commands full current.
> 
> Torque and speed are tied together and are controlled through a motor controller, torque is generally relative to current and speed is generally relative to voltage. The controller will handle both to give the amount of current and voltage needed to satisfy the command. As torque increases, speed increases (until forces at equilibrium) because F=ma.


without nerding out on types of electric motors and torque/speed curves, this is the basic difference in operating characteristics between electric and internal combustion (assuming that is what is intended by "mechanical") motors.


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## Battery (May 7, 2016)

I rode an e-gravel bike and I had to use all of my gearing. I didn't put my bike into max power mode because I wanted to conserve the power for long distance. I ended up riding most of the time in 50 percent power boost mode and got around 70 miles out of my battery. I had to do some nasty climbs and using my whole gear range helped me out a ton. 

Would be interesting if a manufacturer ever built an e-bike with a CVT style transmission. No need for gear shifting!


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## 2old (Aug 31, 2015)

derkommissar said:


> I was just thinking Teslas don't have transmissions. If the point of adding a motor to a bicycle is to augment the rider's power why is there a need for gears at all? Couldn't the motor provide all the assistance needed for climbing hills or going fast on flats?


If a Tesla doesn't have a transmission, how does it move?

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## 2old (Aug 31, 2015)

ctrailbiker said:


> A motor that powerful would probably change the ebike's classification and be illegal on many trails that currently allow ebikes. With that much power an ebike would actually do the kind of damage to trails that many early on feared. Such as peeling out in the dirt etc. You would also need some sort of mechanism like gearing for the rider who needs to be able to pedal at a comfortable cadence.
> 
> Tesla's for example have very powerful motors in them and don't have a transmission, Chevy volts on the other hand have weaker motors and have a CVT transmission in them.


Volt uses a 4ET50,depending on year,not a CVT

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## 2old (Aug 31, 2015)

derkommissar said:


> Also a side thought what means does an electric motor have manage torque and speed the way a mechanical motor does through a gear box?


Voltage/current could be a way

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## derkommissar (Jan 23, 2019)

wolfmw said:


> without nerding out on types of electric motors and torque/speed curves, this is the basic difference in operating characteristics between electric and internal combustion (assuming that is what is intended by "mechanical") motors.


In the case of bicycles the mechnical motor would be the cyclist. So the technology hasn't advanced to the point where we could package the battery and motor strong enough or small enough to replace the gears on a bicycle?


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## .WestCoastHucker. (Jan 14, 2004)

2old said:


> If a Tesla doesn't have a transmission, how does it move?
> 
> Sent from my SM-G930V using Tapatalk


it uses a single reduction gear connected directly to the wheels


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## Shark (Feb 4, 2006)

Assuming electric cars use some type pulse width or pulse amplitude modulation in place of transmission....

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## 2old (Aug 31, 2015)

.WestCoastHucker. said:


> it uses a single reduction gear connected directly to the wheels


Each wheel?

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## .WestCoastHucker. (Jan 14, 2004)

yes. teslas are awd. one motor powers the rear wheels and the front each have their own motors


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## Le Duke (Mar 23, 2009)

.WestCoastHucker. said:


> yes. teslas are awd. one motor powers the rear wheels and the front each have their own motors


They also make single motor cars, or did, that only powered one axle.

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## DtEW (Jun 14, 2004)

.WestCoastHucker. said:


> yes. teslas are awd. one motor powers the rear wheels and the front each have their own motors


While most Teslas are AWD, some are RWD.

RWD Teslas have a single permanent-magnet/reluctance motor in the rear.

Most Teslas that are AWD have a single induction motor in the front, and a single permanent-magnet/reluctance motor in the rear.

The Model S Plaid (and presumably the upcoming top-end Cybertruck) have a single permanent-magnet/reluctance motor in the front, and two permanent-magnet/reluctance motors in the rear for torque-vectoring.

And here's a great video that explains induction/permanent-magnet/reluctance motors as it relates to Teslas, and even a bit on the Prius.


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## EdWiser (Feb 3, 2021)

EV transmissions.



https://cleantechnica.com/2021/07/27/ev-transmissions-are-awesome/


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## DtEW (Jun 14, 2004)

EdWiser said:


> EV transmissions.
> 
> 
> 
> https://cleantechnica.com/2021/07/27/ev-transmissions-are-awesome/


This is a problematic* article because the argument it makes about why Tesla doesn't use a transmission (that it effectively has two final drive ratios between the two independently-powered axles that it uses in place of a transmission) is outdated. This was true for the first generation Model S, which had induction motors front-and-rear. Current Teslas do not shift their bias between front and rear axles for efficiency-at-speed reasons because the rear permanent-magnet/reluctance motor is the major motor at all times. This is because the permanent-magnet/reluctance technology both 1) overcomes the high-speed efficiency issues of permanent-magnet motors, and 2) exceeds the overall efficiency of the induction motor. It is a more-efficient motor at all typical automotive speeds... except for coasting. That's why (aside from cost) there is still an induction motor in the front for their mainstream products.

* Problematic in that while it might be a valid argument, perhaps one that would be essential for a less technologically-advanced motor technology... the current state-of-the-art in motors renders the argument mostly moot. Can even Tesla's permanent-magnet/reluctance motor benefit from a multi-ratio transmission? Maybe. Everything exhibits an efficiency curve, even one with a remarkably wide high-efficiency plateau. But would it be worth the cost/weight/complexity? Maybe for some extreme performance target, eg. must both hit 0-60mph in 2sec AND have enough gearing to hit 260mph. But not relevant for a mass-produced product.


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## Ghost021 (Jun 1, 2021)

Seems like you’re more thinking along the lines of an electric dirt bike. If so, yes it could absolutely be done. 

Takes it completely out of the bicycle category though and as others have mentioned, would outlaw it on a ton of trails. 


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## CrozCountry (Mar 18, 2011)

I think you are confusing an e-bike with an electric motorcycle. Ebikes need gears because a human paddles them. An electric motorcycle is not human driven, so it does not need gears.


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## chiefsilverback (Dec 20, 2019)

CrozCountry said:


> I think you are confusing an e-bike with an electric motorcycle. Ebikes need gears because a human paddles them. An electric motorcycle is not human driven, so it does not need gears.


Unless it's a class 2 eBike with pedal assist and throttle control&#8230;


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## r-rocket (Jun 23, 2014)

CrozCountry said:


> I think you are confusing an e-bike with an electric motorcycle. Ebikes need gears because a human paddles them. An electric motorcycle is not human driven, so it does not need gears.


Is that why I feel super-human when I drag out my single-speed bike, when I do not need gears when I paddle it?

/s
🤖🤖🤖


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## RBoardman (Dec 27, 2014)

r-rocket said:


> Is that why I feel super-human when I drag out my single-speed bike, when I do not need gears when I paddle it?
> 
> /s


Yes, all paddling single-speeders are superhuman or just crazy.


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## .WestCoastHucker. (Jan 14, 2004)

r-rocket said:


> I do not need gears when I paddle it


Don't paddle it too hard, there is a fine line between tough love and abuse..


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## stevenfallover (Jun 5, 2004)

Hate bait.


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## TwoTone (Jul 5, 2011)

OP how do you expect anyone to explain this to you when you can't grasp the basic difference between an ebike and emotorcycle?


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## 2old (Aug 31, 2015)

.WestCoastHucker. said:


> it uses a single reduction gear connected directly to the wheels


The Hummer ev is the same too.

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## ctrailbiker (Aug 19, 2021)

2old said:


> Volt uses a 4ET50,depending on year,not a CVT
> 
> Sent from my SM-G930V using Tapatalk


Which is often referred to as eCVT. Regardless, the point is that the volt uses a form of a transmission.


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## _CJ (May 1, 2014)

Questions people who have never ridden an ebike ask....


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