FACTOR ONE

Factor ONE Review 2026: The Most Extreme Aero Bike We Sell

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The Factor ONE at a glance

The ONE is one of the most radical bike designs on the market, built purely for aerodynamic performance. The split down tube and wide-mouth fork — the shapes that make it instantly recognisable — are there to manage airflow around the front wheel, not for show. The geometry puts you in the most efficient, most aerodynamic position possible, and the whole frame sits low to the ground, dropping the centre of gravity.

What surprises people is the tyre clearance. For a frame this extreme, there's room for a very usable 35 mm tyre, so a modern 30 or 32 mm road tyre runs with space to spare. Our test bike came with Black Inc wheels and the integrated Black Inc cockpit, as Factor delivers it — a complete race package rather than a frame you finish yourself.

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How the Factor ONE rides

The frame is remarkably solid under power. Out of the saddle, full gas, is where the bike comes into its own: every ounce of effort turns into forward motion, and the sprint performance is superb.

The low centre of gravity gives real stability at speed. It settles into fast corners and windy sections with composure and tracks exactly where you point it — for an aero frame with deep tube sections, the crosswind behaviour is better than you'd expect. It rewards an aggressive, committed style: get low, go hard, and it gives everything back. On open, fast roads it holds its speed impressively.

It's not a soft bike. Compared with the Cervélo S5, the ONE is the firmer, more single-minded of the two — the S5 is the one you'd ride for five hours; the ONE is the one you'd race on Sunday.

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Fit and sizing

The position the ONE is built around is aggressive: low front end, long reach. That makes a bike fit more important here than on any other bike we sell, because the margin for a wrong size is smaller. From the fit data we set frame size, stem length, handlebar width, spacer stack, saddle height, setback and tilt, crank length and cleat position — on an integrated cockpit, those choices are made at build, not adjusted later. Six sizes; we'll tell you which one, not the other way round.

If you're too far from one of our fit studios, we'll find a trusted fitter near you, work from their data and advise on whether the ONE's position genuinely suits your body — and if it doesn't, which bike does.

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Who the Factor ONE is for

If you race criteriums, love flat and fast courses, live for the sprint, or simply want the most extreme aero design available, this is your bike. If your riding is long days in the mountains, look at the Factor Ostro VAM, which keeps most of the aero advantage at a lighter weight and a more forgiving ride.