Favero Assioma Pro MX Review

Every pedal power meter until recently made the same assumption: that you ride a road pedal. Look Keo, SPD-SL, and latterly Speedplay — all single-sided entry, all designed for a stiff road shoe you cannot comfortably walk in. If you clipped in with SPD, your options were a crank meter or nothing.

The Assioma Pro MX ends that. It takes the sensor architecture from Favero's road pedals — the reference product in this category — and builds it into a double-sided SPD platform: 199 g per pedal, an 11.2 mm stack height, a 54 mm Q-factor, and a hardened 6061-T6 aluminum body designed for rock strikes.

It was made for gravel and mountain bikes. The reason it belongs on a site about indoor training is that SPD is what an enormous number of people actually wear in the pain cave, and until now that was a reason they could not have pedal power.

Why an SPD power meter matters indoors

Walk into any well-used pain cave and look at the shoes. A large share of indoor riders use mountain bike shoes with recessed SPD cleats, and the reasons are entirely practical: you can walk to the kitchen mid-ride without clacking across a wooden floor, the uppers are more breathable than a stiff road shoe, and if the same shoes go on a commuter or a gravel bike, that is one pair instead of two.

The problem was that pedal-based power — the easiest kind to own, because it moves between bikes in five minutes and needs no drivetrain research — did not exist on that interface. Riders who wanted power indoors were pushed either to a crank meter with its compatibility matrix, or to changing shoes.

The Pro MX removes the choice. Fit it to the bike that lives on the trainer, ride it, and if you take the bike outdoors the meter goes with it. And because the power comes from the pedals rather than the trainer, your indoor and outdoor numbers come from the same device — which is the cleanest possible answer to the argument our smart trainer vs power meter guide exists to referee.

IAV, and why it is not marketing

Most power meters measure torque and multiply it by an assumed constant angular velocity. That assumption is fine when you are turning smooth circles at a steady cadence and progressively less true the harder you ride — a sprint, a steep out-of-the-saddle effort, or an oval chainring all involve the crank speeding up and slowing down within a single revolution.

Favero's IAV Power System uses a three-axis gyroscope to measure the instantaneous angular velocity rather than assume it, and factors that into every calculation. It is the reason Favero can claim ±1% "in any situation" rather than under ideal conditions, and it is why their pedals became the reference against which others are measured.

Indoors this matters less than outdoors, because trainer riding tends to be smoother than road riding. It matters most in exactly the situations the MX was built for — standing on a loose climb, short surges, oval rings.

The fit numbers are the quiet headline

An 11.2 mm stack height and a 54 mm Q-factor are unusual figures for an off-road pedal and they are worth understanding because they affect your position.

Stackis the distance from the pedal axle to the sole of your shoe. Lower stack puts your foot closer to the axle, which most riders describe as feeling more connected and which marginally changes your effective saddle height. At 11.2 mm the MX is low even by road pedal standards, let alone against the tall platforms typical of off-road pedals.

Q-factor is how far apart the pedals hold your feet. Fifty-four millimeters is narrow — closer to a road pedal than to a typical mountain bike pedal, which suits riders whose natural stance is narrow and who find wide off-road pedals uncomfortable on long efforts.

If you are switching to these from a chunky off-road pedal, expect to revisit your saddle height slightly. If you are switching from a road pedal, the change is small.

The battery is the compromise

Favero quotes at least 60 hours per charge for the dual-sided MX-2. That is the shortest runtime in the Assioma family, and it is short next to a coin-cell meter like the 4iiii Precision 3+, which runs for hundreds of hours on a battery you buy in a supermarket.

Sixty hours is somewhere between three and eight weeks of riding depending on your volume, so charging becomes a habit rather than an afterthought — and the charging clip becomes a thing you need to not lose. For an indoor-focused rider this is genuinely easier than for a bikepacker, because the bike is already next to a plug socket.

Living with them

Installation is a pedal wrench and nothing else. No crank compatibility question, no bottom bracket, no torque procedure — which remains the fundamental advantage of pedal-based power over every other kind. Moving them to a different bike takes about five minutes.

Double-sided entry means you never fumble for the right face, which on a trainer is a small pleasure and on a technical climb is a real one. The clip-in surface is hardened, which is Favero's answer to the fact that off-road pedals get hit.

Run a zero-offset after installation and occasionally afterwards, especially following a big temperature change — our calibration guide covers when it actually matters. Indoors, pair them as the power source and let the trainer handle resistance; our Zwift setup guide walks through that pairing.

Who should buy it

Buy the Pro MX if you ride SPD. That is the whole case and it is a strong one: there is no other pedal meter on that interface with this measurement quality, and the fit numbers are better than the off-road category norm.

Buy the road Assioma Duo if you ride Look Keo, the Garmin Rally RS200 if you ride SPD-SL, or the 4iiii Precision 3+ if price is the binding constraint and you only need one bike covered. Our power meter pedal roundup ranks the whole field.