E-bike assist modes decide how your motor reads your legs — and the two main rules behave very differently. A torque multiplier scales motor output to your own effort: at a 2X setting the motor adds roughly 2 watts for every 1 watt you push into the cranks. Constant power ignores how hard you are pedalling and adds a fixed amount — 200 W, say — the moment the cranks turn. Grin Technologies’ pedal-assist reference at ebikes.ca documents both, along with two variants most riders never hear about. Which one suits you comes down to whether you want the bike to amplify you, or to carry a set share of the load for you.
At Cyberbikes in Leichhardt we set this up on customer bikes most weeks, and the conversation almost always starts in the wrong place — with assist levels (1 to 5) rather than the assist mode underneath them. The level is a volume knob. The mode is the rule the knob turns.
What do e-bike assist modes actually control?
An assist mode is the rule your controller uses to turn sensor readings into motor watts. Everything downstream is just physics: electrical power is volts times amps, so a 48 V system drawing 15 A is pulling 720 W from the battery. Mechanical output is torque times rotational speed — Grin’s power-ratings guide gives the shorthand as watts ≈ torque in newton-metres × rpm × 0.104. The same 20 N·m produces about 209 W at 100 rpm and about 628 W at 300 rpm. Identical torque, triple the power, purely because the wheel is spinning faster.
The sensing hardware comes first. A cadence sensor only knows whether the cranks are turning and how fast; Grin notes that early units used 5 or 6 magnets, 12 poles is now the norm, and 24 or more is increasingly common for faster response. A torque sensor measures the force you apply, usually through a bottom-bracket design that needs a 68 mm shell. If you want the full picture of the hardware difference, we covered torque sensor versus cadence sensor pedal assist separately. This article is about what the controller does with that signal.
How does a torque multiplier assist mode work?
A torque multiplier sets a ratio between your power and the motor’s. Grin lists 0.5X, 1X and 2X as worked examples: at 2X, the motor contributes 2 W of output for every 1 W of human power. Pedal at 100 W and you get about 200 W of motor on top, for roughly 300 W at the wheel. Soft-pedal at 40 W and the motor drops to about 80 W. The bike becomes a proportional amplifier of whatever you are already doing.
Your side of that equation is bigger than most riders assume. Grin’s worked example: a 60 kg person standing on a horizontal 165 mm crank applies about 97 N·m (60 × 9.8 × 0.165). Human power is that torque times your cadence, so a steady 70 rpm spin at modest force sits comfortably in the 80–150 W band for an everyday commuter. Multiply that by two and you have a bike that climbs Leichhardt’s back streets without ever feeling like it is dragging you.
What does a power offset threshold change?
A multiplier with an offset only starts assisting once you exceed a set threshold. Grin cites 50 W as a light-pedalling threshold and 200 W as one that reserves assist mainly for hills and acceleration. Below the threshold, the motor stays out of it entirely.
This is the single most useful setting for anyone who finds their e-bike “surgey” on a shared path. Set a 50 W offset and gentle rolling along the Bay Run stays unassisted and quiet; lean on the pedals at a driveway crossing or the start of a climb and the motor arrives. One number, and the bike stops second-guessing you.
What is constant power assist — and when does it feel better?
Constant power adds a fixed boost regardless of effort. Grin’s example is a flat 200 W of motor output — “the same 200 watts” whether you are grinding up a rise or spinning easily on the flat. There is also a fourth rule, constant-throttle PAS, where an assist setting behaves like a part-open throttle: at 50% assist, Grin notes the bike cruises at roughly half its full speed.
Constant power is the better choice for cargo and for riders who want predictability over feel. If you load 40 kg of shopping onto a rear rack, a multiplier gives you more assist only if you push harder — which is exactly when you are least able to. A fixed 200 W just turns up and stays there. It is also kinder to anyone with a knee or hip that dislikes variable load.
The trade-off is feel. Constant power makes the bike feel like a small motorbike with pedals; a multiplier makes it feel like a bicycle you are unusually strong on. Different products, same frame.
Which e-bike assist mode uses less battery?
Neither, inherently. Grin’s reference is blunt about it: range depends on the average power drawn, not on the control scheme. A torque-based setup tends to stretch range because it shifts more of the propulsion onto your legs, but a 2X multiplier ridden hard will flatten a battery faster than a conservative 150 W constant setting.
The arithmetic that actually predicts your range is simple. Energy stored is volts times amp-hours: the Cyberbikes Centauro runs a 48 V 25 Ah Samsung pack, which its product page lists as 1200 Wh. Divide that by your consumption in watt-hours per kilometre and you have your distance. At 10 Wh/km you get 120 km — which is exactly the figure the page claims, at 25 km/h on flat road with a 75 kg rider and no headwind. Push the average draw to 20 Wh/km with a heavy multiplier setting, a loaded rack and a westerly, and the same pack gives 60 km. The battery did not change. The mode and the conditions did.
There is also a thermal cost to asking for big torque at low speed. Heat in the windings rises with the square of current, so doubling current to double torque quadruples the copper losses — the I²R term. Grin’s measurements show how brutal this gets: one MXUS motor marketed as 5000 W reaches a 100 °C core temperature at 250 rpm while producing just 800 W of output. A mode that pours current in at walking pace is cooking the motor, not helping it.
What does NSW law mean for your assist settings?
No assist mode changes what is legal. Transport for NSW sets the limits on its e-bike page: a maximum of 500 W continuous rated power, a motor that provides no power above 25 km/h, and throttle-only operation that cuts out at 6 km/h. From 1 March 2029 the limit tightens to 250 W with mandatory EN 15194 certification. A bike that exceeds any of those limits is illegal, and the page is explicit that software or app limiting does not fix a non-compliant bike. Under seizure laws that took effect on 21 August 2026, police can seize and dispose of illegal e-bikes.
In practice this means your choice of mode affects the shape of the power delivery below 25 km/h, never the ceiling. The Centauro’s product page lists a 250 W continuous rear hub, with assist cutting at 25 km/h and the throttle limited to 6 km/h.
Which assist mode suits a Sydney commute?
| Mode | What it does | Best for |
|---|---|---|
| Torque multiplier (0.5X–2X) | Motor watts scale with your watts | Fitness, bike-like feel, stretching range |
| Multiplier + offset (50 W / 200 W) | Assist only above a set effort | Shared paths, hills-only assist |
| Constant power (e.g. 200 W) | Fixed boost regardless of effort | Cargo, joint-friendly riding, predictability |
| Constant-throttle PAS (e.g. 50%) | Acts like a part-open throttle | Steady cruising at a capped speed |
For a typical Inner West run — Leichhardt to the CBD, stop-start, a few short rises — a 1X multiplier with a 50 W offset is the setting we fit most often. It saves battery on the flat and arrives with real help the moment you stand on the pedals. For a parent doing the school run with a kid and a bag of gear, moderate constant power wins: the load does not vary with how energetic you feel that morning.
You can see how the Centauro behaves under load in our own road testing:
If you want the whole chain — sensor to controller to motor — laid out in one place, start with our guide to how e-bikes actually work: motors, sensors and controllers.
Frequently asked questions
Is a torque multiplier the same thing as a torque sensor?
No. A torque sensor is the hardware that measures how hard you push on the cranks. A torque multiplier is the control rule the controller applies to that reading, setting how many watts of motor power you get per watt of your own — 0.5X, 1X or 2X in Grin Technologies’ examples at ebikes.ca. You need the sensor to use the multiplier, but the same sensor can also drive a constant-power mode.
Does a higher assist level make my e-bike faster?
Not past the legal ceiling. Transport for NSW requires that the motor provides no power above 25 km/h, and throttle-only operation must cut out at 6 km/h. A higher assist level means the motor supplies a larger share of the work needed to reach and hold that speed, so you arrive less tired — not that the bike goes faster.
Which e-bike assist mode gives the longest range?
Whichever one results in the lowest average motor power over your ride. Grin Technologies states that range depends on the average power drawn rather than the control scheme itself. In practice a torque multiplier with an offset usually wins, because it leaves gentle sections unassisted, but a low constant-power setting can match it.
Try both modes before you choose
Reading about assist modes gets you halfway. Feeling the difference between a 2X multiplier and a flat 200 W on the same hill gets you the rest. Book a test ride at Cyberbikes, 281 Parramatta Road, Leichhardt and we will set a Centauro up both ways so you can ride them back to back. Call 0491 794 668, Tuesday to Saturday, and ask for a setup session — it takes ten minutes and it is the difference between an e-bike you tolerate and one you actually enjoy.
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