Sizing a Factor road bike
Factor is a race brand, and its road bikes are sized like race bikes: low at the front, long in reach, built for riders who want a committed position. The reassuring part is that Factor does not run small or large in any surprising way. A 56 Ostro VAM sits right in line with a Cervélo S5 or a Giant TCR, so the smart move is to compare stack and reach with a bike you already know rather than reading anything into the number. Factor itself sizes riders through a fit form reviewed by an in house fitter, so the ranges below are a starting point, not an official chart.
See the Factor range at Bikeroom as you go.
Important. Factor deliberately does not publish per size height ranges; it prefers a personalised fit form. The heights below are a widely used third party synthesis, useful for orientation only. Compare stack and reach, and confirm with a fitter before buying.
Size at a glance
The Ostro VAM, O2 VAM and Monza share the same numbered sizes, 45 to 61, and a common fit envelope. Find your height, check your inseam, then pick the model by how upright you want to sit: Ostro lowest, O2 and Monza a little taller.
| Rider height | Leg length (inseam) | Ostro VAM (aero) | O2 VAM (climbing) | Monza (race) |
|---|---|---|---|---|
| 152 to 160 cm | 68 to 74 cm | 45 | 45 | 45 |
| 158 to 168 cm | 73 to 78 cm | 49 | 49 | 49 |
| 167 to 173 cm | 77 to 82 cm | 52 | 52 | 52 |
| 172 to 178 cm | 81 to 86 cm | 54 | 54 | 54 |
| 177 to 183 cm | 85 to 89 cm | 56 | 56 | 56 |
| 182 to 188 cm | 88 to 92 cm | 58 | 58 | 58 |
| 187 to 195 cm | 91 to 97 cm | 61 | 61 | 61 |
Factor's own rule of thumb: a rider around 180 cm usually starts on a 56. Use that as a reference point and adjust from your stack and reach.
Taking your measurements
Measure height barefoot to the wall, up to the top of your head. For inseam, hold a book against the wall between your legs like a saddle and measure floor to spine. Inseam in centimetres times 0.66 gives a rough frame size, but on a pure race brand the more valuable check is matching stack and reach to a bike you already ride in a position you like.
The road range
Ostro VAM (aero all rounder)
The Ostro VAM is Factor's do it all aero race bike, long and low but liveable, with a stack to reach that mirrors the mainstream fast bikes. A few spacers give a marginally more relaxed setup. Sizes: 45, 49, 52, 54, 56, 58 and 61.
| Frame size | 45 | 49 | 52 | 54 | 56 | 58 | 61 |
|---|---|---|---|---|---|---|---|
| Stack (mm) | 502 | 503 | 523 | 542 | 565 | 587 | 611 |
| Reach (mm) | 360 | 370 | 376 | 384 | 392 | 401 | 409 |
| Rider height | 152 to 160 | 158 to 168 | 167 to 173 | 172 to 178 | 177 to 183 | 182 to 188 | 187 to 195 |
A true WorldTour race fit. If you want endurance comfort, this is not the bike, though a modest spacer stack softens it.
O2 VAM (climbing)
The O2 VAM is the featherweight climber. It shares the Ostro's handling and rider position philosophy but sits roughly 10 mm taller in stack with a slightly shorter reach, a touch more upright for long ascents. Sizes: 45, 49, 52, 54, 56, 58 and 61.
| Frame size | 45 | 49 | 52 | 54 | 56 | 58 | 61 |
|---|---|---|---|---|---|---|---|
| Stack (mm) | 502 | 514 | 535 | 552 | 574 | 597 | 611 |
| Reach (mm) | 360 | 367 | 373 | 381 | 389 | 401 | 410 |
| Rider height | 152 to 160 | 158 to 168 | 167 to 173 | 172 to 178 | 177 to 183 | 182 to 188 | 187 to 195 |
Same rider position family as the Ostro, just a little higher at the front. Riders who ran an older Ostro with spacers often land here naturally.
Monza (amateur race)
The Monza is the real world race bike, pitched below the Ostro with a slightly taller, more democratic fit that opens the hip angle a touch. It uses the same stack and reach as the O2 VAM. Sizes: 45, 49, 52, 54, 56, 58 and 61.
| Frame size | 45 | 49 | 52 | 54 | 56 | 58 | 61 |
|---|---|---|---|---|---|---|---|
| Stack (mm) | 502 | 514 | 535 | 552 | 574 | 597 | 611 |
| Reach (mm) | 360 | 367 | 373 | 381 | 389 | 401 | 410 |
| Rider height | 152 to 160 | 158 to 168 | 167 to 173 | 172 to 178 | 177 to 183 | 182 to 188 | 187 to 195 |
The most accessible Factor fit. Reviewers note the reach can feel a hair long and that the 58 ships with a longer than usual 120 mm stem, so a shorter stem is an easy adjustment.
Above these sits the ONE, Factor's new flagship aero bike. It uses a proprietary integrated cockpit and a five size scheme rather than a conventional stack and reach chart, so it is best sized through Factor's fit form rather than a table. If the ONE is on your shortlist, talk to us and we will run the numbers with you.
What Factor riders report
The clear consensus is that Factor road bikes track the mainstream on fit, so a 56 here feels like a 56 on the fast bikes you already know. That makes stack and reach the reliable comparison. These are race bikes, so they reward flexibility and a strong core, and endurance riders or newcomers are gently steered elsewhere or toward a few spacers. Between two sizes, most experienced riders go smaller for a lower, nimbler bike and raise it as needed, sizing up only for a long torso or a preference for stretched out stability. One practical caveat runs across the range: the integrated Black Inc cockpit fixes bar width and stem length at purchase and is expensive to change, so the pre order fit matters for the cockpit as much as the frame.
Between two sizes?
Smaller for racy and quick, larger for stable and stretched. Since these are committed race bikes, only size up if your proportions or comfort clearly call for it. When it is close, or if you are eyeing the ONE, send us your height, inseam and current stack and reach and we will pin it down.
Shop Factor
- Factor Ostro VAM for aero all round racing
- Factor O2 VAM for lightweight climbing
- All Factor bikes including the Monza and the ONE
Cockpit and frame in one go: ask our concierge
Because Factor's cockpit is set at purchase, getting size and spec right together pays off. Share your height, inseam and current stack and reach with our concierge team and we will recommend the frame, size and cockpit. Talk to our concierge.
These sizes are orientation only, not a fitting guarantee. Factor does not publish official per size height ranges and sizes riders through a fitter reviewed form, so the height bands are a third party synthesis. The ONE is sized separately via that form. Geometry reflects current Factor data and can change between model years, so confirm against the specific bike you are buying.
