On a mid-drive e-bike, e-bike gears change battery use directly — a lower gear on a climb and a higher gear on the flat both keep the motor spinning in its efficient range. On a hub-motor e-bike like the Cyberbikes Centauro, shifting barely touches the motor at all: the motor is bolted inside the wheel, so its RPM is set by your road speed, and the gear only decides how much of the work your legs take off the battery. Both effects are real, and both are worth watts.
That distinction is the whole answer, and almost nobody explains it. Below we work through what the drivetrain actually does to the current your controller pulls, why the wrong gear heats a motor far faster than it flattens a battery, and what we tell riders to do on the climbs around Leichhardt.
Do e-bike gears actually change how much battery you use?
Your battery does not know what gear you are in. It only sees watts, and watts are simple: watts = volts × amps. A 48 V pack delivering 15 A is putting out 720 W, whatever the cassette is doing. Grin Technologies, whose pedal-assist engineering notes are the closest thing this industry has to a textbook, put it plainly: “The range you get on an ebike fundamentally has nothing to do with what kind of control system you use, and everything to do with the average amount of power you draw.”
So the only question worth asking is whether shifting changes the average watts. The energy side is just as simple: watt-hours = volts × amp-hours. The Centauro’s 48 V 25 Ah Samsung pack is listed on its product page as 1200 Wh. Divide that by your real consumption and you get range: at 12 Wh/km that 1200 Wh is about 100 km of arithmetic; thrash it at 20 Wh/km and the same pack is nearer 60 km. Gear choice moves the Wh/km number. It never moves the 1200.
Why does gear choice matter on a mid-drive but not a hub motor?
A mid-drive motor turns the chainring, so its torque and speed pass through your gears. Shift down and the motor spins faster for the same road speed — and motor power is torque multiplied by RPM. Grin’s page on motor power ratings gives the arithmetic: “A motor producing 20 Nm of torque and spinning at 100 rpm is generating 209 watts. That same motor… at 300 rpm is producing 628 watts.” Three times the output from identical torque, purely because of gearing. That is why mid-drives climb so well when you shift properly and bog down embarrassingly when you don’t.
A hub motor is the wheel, so its RPM is locked to your road speed and tyre size. Riding at 20 km/h on 26 × 2.4 tyres is exactly the same motor RPM in first gear as in seventh. No amount of shifting moves the motor’s operating point. What shifting does move is your own contribution: a rider holding a steady 100 W is 100 W the battery never has to supply, and at commuting speeds that can be a fifth or more of the total demand. Pick a gear you can actually spin and you are effectively riding a bigger battery. If the difference between the two layouts is new to you, our guide to how mid-drive and hub motors each actually work covers it properly, and the full picture of controllers and sensors lives in our guide to how e-bikes actually work: motors, sensors and controllers.
How does the wrong gear overheat an e-bike motor?
Heat comes from current, not from power. Grin state it directly: “It’s not the output power but the output torque of the motor which causes it to heat up.” Winding losses follow an I²R relationship — double the current and you get four times the heat. That is why a motor can cruise at 600 W on the flat all day and cook itself at 400 W crawling up a hill: the slow climb needs far more amps for far fewer watts, with barely any airflow over the shell.
The good news is that motors are tougher than riders think. Grin note that motor cores run to 150–180 °C on high-temperature enamel without damage, that thermal equilibrium takes one to two hours to reach, and that motors routinely handle far more than their continuous rating for a climb lasting five to ten minutes. No Sydney hill is five to ten minutes long. What does the damage is the daily version: a loaded bike, a high gear, a rider not pedalling, and a controller quietly pulling its current limit every morning. Grin’s motor simulator will even predict the temperature curve and the overheat time for a given hill and load, and it makes an uncomfortable point: a setup running at 80% efficiency can still draw more power over the same distance than one at 75%.
Which gear should you use on a Sydney hill start?
Shift down before you stop, not after. Pulling away from the lights on Parramatta Road in a high gear is the single most expensive habit we see in the workshop: your legs contribute nothing, the controller dumps its maximum current into a motor turning at almost zero RPM, and on a torque-sensing bike you get a weak, laggy start on top of it. Two or three gears down as you roll to a stop fixes all of it.
- Starting and climbing: a gear you can spin at a comfortable cadence, not one you have to stamp on.
- Flat and into a headwind: a higher gear and a steady cadence — you are fighting air, not gravity, and the motor is already in its happy range.
- Loaded up: gear down earlier than feels necessary. The Centauro’s rear rack is rated to 50 kg and that weight does not disappear on a climb.
- On the throttle: gears do nothing at all. The motor drives the wheel directly and your legs are out of the circuit — which is one reason throttle riding drains a pack faster.
Does NSW law care what gear you are in?
No — NSW law regulates the motor, never the drivetrain. Transport for NSW currently sets a maximum continuous rated power of 500 W, dropping to 250 W with mandatory EN 15194 certification from 1 March 2029. Pedal assistance must stop at 25 km/h and throttle-only power must cut out at 6 km/h. The department is explicit that a bike exceeding those limits “are illegal, even if its power or speed is restricted by an app or switch” — so a software limit is not a defence.
The practical consequence for gearing is neat: above 25 km/h you are on your own regardless of gear, because the motor has legally stopped helping. That is exactly when a higher gear earns its keep, and exactly when a rider who has been freewheeling in the wrong gear discovers they have no top end at all.
What does this mean on the Cyberbikes Centauro?
The Centauro is a rear hub-motor bike, so everything in the hub-motor column above applies to it. Its product page lists a 250 W rear hub motor, a 48 V 25 Ah (1200 Wh) Samsung battery certified to UL 2271, a full system certified to UL 2849, an ISO 4210 frame, EN 15194 compliance, assistance to 25 km/h with a 6 km/h throttle, 26 × 2.4 tyres, 100 mm front and 120 mm rear suspension travel, four-piston hydraulic brakes on 180 mm × 2.3 mm rotors, a 150 kg combined rider-and-cargo limit, a 50 kg rear rack, an optional 15 kg front basket and an 18-month warranty.
On a bike like that, shifting will not change what the motor is doing — but it absolutely changes what you are doing, and your legs are the cheapest power source on the bike. Riders who gear down and keep spinning routinely get a meaningful chunk more out of the same pack than riders who sit in one gear and let the motor carry everything. If you want the rest of the energy side, our definitive guide to e-bike batteries covers cells, charging and how range really gets spent.
Watch: the Centauro up close
Frequently asked questions
Does shifting gears save battery on a hub-motor e-bike?
Indirectly, yes. A hub motor sits in the wheel, so its RPM is fixed by road speed and shifting cannot change its operating point. What shifting changes is how much power your legs contribute, and every watt from your legs is a watt the battery does not supply. Choosing a gear you can spin comfortably is the practical way to cut watt-hours per kilometre on a hub-motor e-bike.
Should I start from a standstill in a low gear on an e-bike?
Yes. Shift down two or three gears as you roll to a stop. Starting in a high gear means your legs add almost nothing while the controller pulls its maximum current into a motor turning at nearly zero RPM, which is the least efficient and hottest condition a motor ever sees. A low gear at the lights gives a smoother start, less heat and less battery drain.
Does the wrong gear make an e-bike motor overheat?
It can. Grin Technologies note that it is output torque rather than output power that heats a motor, and winding losses follow an I²R relationship, so doubling the current gives four times the heat. Grinding up a long climb slowly in a high gear draws high current at low airflow. Motor cores tolerate 150–180 °C and handle five to ten minute climbs comfortably, but repeating that daily on a loaded bike is what triggers power cut-backs.
Come and feel the difference
The fastest way to understand any of this is thirty seconds on a hill. Book a test ride at Cyberbikes Leichhardt, 281 Parramatta Road, and we will set your gearing and assist levels up properly before you ride away — call 0491 794 668, Tuesday to Saturday, or browse the range at cyberbikes.com. Rent-to-own starts from $99.99 a week if you would rather ride now and decide later.
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