Colnago builds one time trial frame, the TT1, and offers it in three sizes: S, M and L. On its road bikes the brand sizes Italian style, measuring the seat tube from the centre of the bottom bracket to the seatpost node. For the TT1 it says something different and more useful: the choice depends on the stack and reach you want for the aero components. That sentence is this whole guide in miniature. Browse all Colnago bikes at Bikeroom.
Please note. The suggestions here are indicative only, a starting point and not a guarantee of fit. Your ideal size moves with torso and arm length, flexibility and how far forward you intend to sit. Confirm the choice with a professional bike fit or with our team before you buy.
Quick size finder
Colnago publishes a rider height table for the TT1, so this one is the brand's own work rather than an estimate. It lists S/M and M/L rows even though only three frames exist. Those are the heights where Colnago accepts that either frame can be made to work.
| Rider height | Leg length (inseam) | Saddle height (Colnago) | TT1 size |
|---|---|---|---|
| 155 to 161 cm | 68 to 72 cm | 60.5 to 64 cm | S |
| 164 to 167 cm | 73 to 75 cm | 65 to 66.5 cm | S |
| 170 cm | 77 cm | 68.5 cm | S or M |
| 172 to 174 cm | 79 to 81 cm | 70.5 to 72 cm | M |
| 176 to 178 cm | 83 to 85 cm | 73.5 to 75.5 cm | M or L |
| 180 to 186 cm | 86 to 89 cm | 76.5 to 79 cm | L |
| 188 to 196 cm | 90 to 94 cm | 80 to 83.5 cm | L |
Colnago labels the two overlap rows S/M and M/L. The saddle height column is Colnago's own approximation and moves with flexibility and pedalling style.
How to measure yourself
Height. Stand barefoot with your back to a wall, heels together, and measure to the top of your head.
Leg length (inseam). Barefoot, feet about 15 cm apart, press a book up between your legs as if it were a saddle. Keep it level against the wall and measure from the floor to the top edge.
The inseam formula. Colnago's road sizes are numeric, so multiplying your inseam in centimetres by 0.66 gives a usable road number. It tells you nothing about the TT1, which is lettered and fitted from the armrests. Use the table above, then the geometry below.
Colnago TT1 (time trial and triathlon)
The TT1 replaced the K.One, moved to disc brakes and swapped a sloping top tube for a horizontal one. Colnago shortened the head tube on purpose. BikeRadar reported at the launch that the lower front end is meant to be built back up with spacers under the elbow rests. That is how a short head tube becomes a fit advantage rather than a limit. The frame takes electronic groupsets only and clears a 28 mm tyre with 4 mm to spare.
| Size | Stack (mm) | Reach (mm) | Seat tube angle | Head tube angle | Chainstay (mm) | Rider height |
|---|---|---|---|---|---|---|
| S | 471.7 | 396.5 | 77° | 72° | 400 | 155 to 170 cm |
| M | 490.7 | 406.5 | 77° | 72° | 400 | 170 to 178 cm |
| L | 490.7 | 426.5 | 77° | 72° | 400 | 176 to 196 cm |
Fit character: the M and the L share a stack of 490.7 mm. Choosing between them is a 20 mm reach decision at one front end height.
Colnago publishes no seat tube length, head tube length, standover figure or frame weight for the TT1. It no longer publishes a geometry chart for the older K.One either. Where a value is missing here, it is missing from the official chart.
From a Colnago road size to a TT1 size
Colnago runs both its road chart and its TT1 chart against the same rider height and inseam rows, so the two can be read side by side. This is the clearest way to see what the old rule of thumb really means.
| Rider height | Colnago road size (V5Rs, V4Rs, C68) | TT1 size |
|---|---|---|
| 161 cm | 420 | S |
| 167 cm | 455 | S |
| 172 cm | 485 | M |
| 176 cm | 485 | M or L |
| 180 cm | 510 | L |
| 186 cm | 530 | L |
| 192 cm | 570 | L |
Three lettered time trial sizes cover the span of seven road numbers. That compression is what riders mean when they say a time trial frame runs a size smaller.
Why a time trial size is not a road size
- Pad stack and pad reach replace stack and reach. The measurement that decides your position runs from the bottom bracket to the armrest, not to the top of the head tube.
- The seat angle gets steeper. Road frames sit near 73 degrees. The TT1 runs 77 degrees at all three sizes, inside the 76 to 80 degree band typical of time trial and triathlon frames, which rotates the rider forward and opens the hip angle.
- Most riders drop a size. A shorter head tube and shorter reach leave room to build the position back up with spacers under the pads.
- The rules differ. UCI time trial racing limits saddle setback and extension length. Triathlon has no equivalent limit, so the same TT1 can be ridden further forward in a non UCI race.
What riders say about Colnago TT1 sizing
The TT1 is a low volume race frame. There is far less owner feedback than for a Colnago road bike, and what exists is mostly press coverage and pro bike galleries. Three points recur.
The short head tube is the design decision people notice first. BikeRadar's launch piece by Stan Portus, published on 4 May 2022, framed it as a trade. You get less frontal area at the head tube, and you add spacers under the elbow rests to get back to your number.
Colnago's own guidance points the same way. Rather than a height rule, it tells TT1 buyers that the choice depends on the stack and reach they want for the aero components.
Pro bikes are a poor guide here. Cyclist's look at Tadej Pogačar's TT1, by Ewan Wilson on 9 July 2025, describes a custom Enve cockpit with notably steep extensions. That is not the stock fit window, so do not size yourself from a race photograph.
Between two sizes?
Between the S and the M you are choosing 19 mm of stack and 10 mm of reach at once, so the smaller frame genuinely sits lower and shorter. Between the M and the L the stack is identical, so the question is only whether you want 20 mm more reach.
Long arms and a long torso point to the larger frame. A shorter torso, or a plan to go lower over the next two seasons, points to the smaller one and a taller spacer stack. Because the cockpit and the seatpost do the fine work on this frame, a fit session before you buy is worth more than any height chart.
Our Colnago road bike size guide covers the numeric road range. If you are weighing a UCI legal frame against a triathlon one, time trial bicycles versus triathlon bicycles explains what each set of rules allows. For context on how these frames are used at the top level, see our piece on the time trial bikes of the Vuelta.
Shop Colnago at Bikeroom
- All Colnago bikes for the full range.
- Colnago road bikes if a road frame is the better buy.
- Time trial and triathlon bikes for the whole category across brands.
- Triathlon framesets if you already own the cockpit and the wheels.
If you ride a 52s Colnago on the road and cannot tell whether that means a TT1 in M or in L, talk to our concierge. We will work it through against your fit numbers.
Disclaimer: the size suggestions here are indicative only and do not guarantee a correct fit. Geometry figures are official Colnago data taken from the TT1 product page and the TT1 Geometry Chart, and the rider height, inseam and saddle height figures come from Colnago's published size guide. Values Colnago does not publish are marked as such rather than estimated. Always confirm against the exact bike and model year you are buying.
Sources: Colnago, TT1 product page; Colnago, TT1 Geometry Chart; Colnago, size guide; BikeRadar, Stan Portus, 4 May 2022; Cyclist, Ewan Wilson, 9 July 2025. All accessed 24 September 2026.
