Short answer: yes — a smaller wheel climbs better, and the motor never changes. Put the same hub motor, controller and battery into a 26-inch wheel instead of a 29-inch one and the motor spins roughly 10% faster at the same road speed, so it needs about 9% less torque to push you just as hard. Torque is what heats a hub motor, so that smaller wheel also runs around 16% cooler on a long climb. Grin Technologies, who build and bench-test hub motors in Vancouver, put the effect bluntly: lace the same motor into a 20-inch wheel rather than a 26-inch one and its continuous rating goes from 500 watts to 650 watts. Same copper, same magnets — just more RPM.
That is the whole trick, and it is why e-bike wheel size matters more than the sticker on the motor. At Cyberbikes in Leichhardt we get asked for “a bigger motor” for Sydney hills most weeks. Often the cheaper, cooler, more legal answer is a smaller wheel.
Why does a smaller wheel climb better if the motor is identical?
Because the wheel is a lever, and a bigger wheel is a longer one. The motor sits at the hub and twists; what pushes you up the hill is the force at the contact patch, out at the rim. Torque equals force times lever arm, so the force you get is motor torque divided by wheel radius. Make the radius bigger and the same torque produces less push.
Real numbers, using a 2.4-inch tyre on each rim. A 26-inch wheel comes out around 681 mm across, so the radius is 0.34 m. A 29-inch wheel is about 744 mm, a radius of 0.372 m. To put 100 newtons of push into the road — roughly what a steady suburban climb asks of the motor — the 26-inch wheel needs 34.0 Nm at the hub and the 29-inch wheel needs 37.2 Nm. The 29er is asking its motor for 9% more twist to do exactly the same work.
Grin makes the same point from the other direction in their hub motor selection guide: on any vehicle where the front and rear wheels are different sizes, you always get the best motor performance by putting the hub drive in the smaller of the two.
What does wheel size do to your motor’s power rating?
It changes it completely, because power is not a property of a motor sitting on a shelf. Power is torque multiplied by how fast the thing is spinning. Grin give the formula plainly: Power in watts = torque × RPM × 0.104. The same motor holding 20 Nm produces 209 W at 100 rpm and 628 W at 300 rpm. Nothing about the motor changed. Only the RPM did.
Your wheel is what sets that RPM. At a fixed road speed, a smaller wheel has to turn more times per minute to cover the same ground — and a hub motor turns exactly as fast as its wheel. Grin’s own reference point is a 26-inch wheel doing 32 km/h, which works out at about 250 rpm; our arithmetic for a 26 × 2.4 tyre gives 249 rpm, so the maths lines up.
Here is the same comparison at the 25 km/h where NSW pedal assist cuts out, which is where a Sydney rider actually lives:
| Wheel (2.4″ tyre) | Motor RPM at 25 km/h | Hub torque for 100 N of push | Relative winding heat |
|---|---|---|---|
| 20-inch | 251 rpm | 26.4 Nm | 0.60× (40% cooler) |
| 24-inch | 211 rpm | 31.4 Nm | 0.85× |
| 26-inch | 195 rpm | 34.0 Nm | 1.00× (baseline) |
| 27.5-inch | 188 rpm | 35.3 Nm | 1.07× |
| 29-inch | 178 rpm | 37.2 Nm | 1.19× (19% hotter) |
How much hotter does a big wheel run on a long climb?
Hotter than most riders expect, because heat does not rise in step with torque — it rises with the square of it. Grin spell out the mechanism: the current through the copper windings is what produces almost all the heat inside a hub motor, and if you double the current to get double the torque, you get four times the copper heat. That is the I²R relationship, and it is the single most useful thing to understand about why e-bike motors fail.
So what does that mean for a 29er versus a 26er?
The 29-inch wheel needs 9% more torque for the same push, and 1.09 squared is about 1.19 — so roughly 19% more heat dumped into the windings for an identical climb. Go the other way, to a 20-inch wheel, and you are at 0.60× the heat: a 40% reduction, for free, with no change to the motor at all.
The saving grace is time. Grin note that a hub motor takes one to two hours to reach a steady temperature, while the steepest climbs most riders meet are over in five to ten minutes. That thermal mass is why a 250 W motor survives a hill that, on paper, asks far more of it. But stack a heavy cargo load, a hot Sydney afternoon and a sustained grade and the margin is real — and your wheel quietly sets how big it is.
Does a bigger wheel buy you more speed or more range?
Not much of either, and this is where the marketing and the physics part company.
Speed: on a legal NSW e-bike it is a non-question. Pedal assist has to stop at 25 km/h whatever wheel you fit, so a bigger wheel cannot give you a higher assisted top speed. All it does is move where in the motor’s curve you are sitting when you get there.
Range: range comes from energy and efficiency, not diameter. Energy is just volts times amp-hours — a 48 V 25 Ah pack holds 48 × 25 = 1200 Wh. Divide that by how many watt-hours you burn per kilometre and you have your range. The Cyberbikes Centauro product page quotes up to 120 km at 25 km/h on flat road with a 75 kg rider and no headwind, which works out at about 10 Wh/km. What moves that number is tyre pressure, rider weight, wind and hills — not whether your rim is 26 or 29 inches.
Where a bigger wheel genuinely wins is ride quality: it rolls over potholes, tram tracks and kerb lips with a shallower angle of attack. That is a real benefit on Sydney roads. It is just not a power or range benefit, and it is paid for in motor heat. If you want the deeper picture on how the motor, sensor and controller work together to deliver that torque, our guide to how e-bikes actually work: motors, sensors and controllers covers the whole chain.
Why does the Cyberbikes Centauro run 26-inch wheels?
Because it is built to carry things, and carrying things is exactly where wheel-size torque maths bites hardest. The Centauro’s published specs list 26 × 2.4 e-bike-rated tyres, a 250 W rear hub motor, a 48 V 25 Ah (1200 Wh) Samsung battery, a 37 kg kerb weight and a 150 kg maximum combined rider-and-cargo load, with the welded rear rack rated to 50 kg on its own.
Run the numbers on that. A fully loaded Centauro can be pushing 187 kg of bike and cargo up a hill. Every extra kilo is extra force at the contact patch, which is extra torque at the hub, which is heat squared. Moving that bike to 29-inch wheels would hand the motor a 19% heat penalty on precisely the ride it was designed for. The 26-inch wheel is not a cost compromise — it is the thermal headroom that lets a modest, road-legal 250 W motor haul a 50 kg rack up Leichhardt’s back streets without cooking.
Geared hubs stack the same trick inside the shell: Grin list “better hill climbing efficiency” as a core advantage of geared over direct drive, because the internal reduction lets a small motor spin fast while the wheel turns slowly. Our comparison of direct drive versus geared hub motors covers the trade-offs.
Does wheel size change what is legal in NSW?
No. The law regulates power and speed, not rims. Transport for NSW currently sets a maximum continuous rated power of 500 W, with that dropping to 250 W and mandatory EN 15194 certification from 1 March 2029. Motor power must cut out completely at 25 km/h, and throttle-only operation must cut out at 6 km/h. A bike over those limits is illegal even if its power or speed is restricted by an app or a switch, and since 21 August 2026 police and authorised officers can seize and dispose of illegal e-bikes used on roads and road-related areas. Helmets are mandatory for riders and passengers.
Here is the quiet upside of the wheel-size argument: it gets you more climbing out of a motor that is already inside the law. You cannot legally buy your way up a hill with watts. You can absolutely engineer your way up one with RPM. The Centauro’s product page lists a 250 W continuous motor, 25 km/h assist and a 6 km/h throttle, plus UL 2849 for the e-bike system, UL 2271 for the battery and ISO 4210 for the frame.
See it on a real climb
Theory is cheap. This clip from the Cyberbikes channel shows the practical side — what actually gets a loaded e-bike up a steep grade without burying the motor:
Frequently Asked Questions
Do smaller wheels make an e-bike climb better?
Yes. With the same motor, controller and battery, a smaller wheel turns the motor faster at any given road speed, so the motor produces the same push with less torque. A 26-inch wheel needs about 9% less hub torque than a 29-inch wheel for the same force at the road, and because winding heat rises with the square of torque, it also runs roughly 16% cooler on a sustained climb.
Does a bigger e-bike wheel reduce your range?
Barely. Range is set by battery energy and watt-hours per kilometre, not wheel diameter. A 48 V 25 Ah battery holds 1200 Wh, and the Cyberbikes Centauro is quoted at up to 120 km at 25 km/h on flat road with a 75 kg rider and no headwind, which is about 10 Wh/km. Tyre pressure, rider and cargo weight, wind and hills move that figure far more than rim size does.
Can a bigger wheel make an e-bike go faster than 25 km/h in NSW?
No. Transport for NSW requires motor power to cut out completely at 25 km/h regardless of wheel size, with throttle-only operation cutting out at 6 km/h and a maximum continuous rated power of 500 W, falling to 250 W with mandatory EN 15194 certification from 1 March 2029. A bike above those limits is illegal even if it is restricted by an app or a switch.
Ride one up a real hill before you decide
Specs on a page will not tell you how a 26-inch wheel feels at 15% grade with shopping on the rack. Ten minutes on the bike will. Come and test ride the 2026 Cyberbikes Centauro at 281 Parramatta Road, Leichhardt — test rides are free, and the hills around the shop are honest ones. Call 0491 794 668, Tuesday to Saturday, or ask us about rent-to-own from $99 a week if you would rather start riding before you start buying.
#Cyberbikes #EbikeSydney #WheelSize #HubMotor #ElectricBikeLeichhardt #CentauroEbike #EbikeTech #RentToOwn #SydneyCommute
