Sizing a 3T gravel bike
3T pioneered the aero gravel bike, and the current range fans out from that idea: the Racemax for fast racing, the Ultra for comfort and adventure, the Extrema for the roughest terrain, and the Primo for a road like all rounder. Two things to know. The current frames run longer and taller than the original Exploro, so riders coming off an old Exploro often size down to keep their position. And most models take both 700c and 650b wheels, which 3T engineers to keep handling consistent, so the wheel choice is about tyre volume and terrain rather than fit.
Browse the range: all 3T bikes at Bikeroom.
Please note. These sizes are a starting point, not a guarantee. 3T itself stresses comparing stack and reach to your current bike over any height chart, so treat the height bands as a guide and confirm with a fit where you can.
Quick size finder
Find your height, cross check your inside leg, and read across. Only the Racemax reaches down to XS and up to XXL; the other four run S to XL.
| Rider height | Leg length (inseam) | Racemax | Racemax² Italia | Ultra² Italia | Extrema Italia | Primo² |
|---|---|---|---|---|---|---|
| 145 to 157 cm | 66 to 74 cm | XS | — | — | — | — |
| 157 to 168 cm | 74 to 80 cm | S | S | S | S | S |
| 168 to 176 cm | 79 to 84 cm | M | M | M | M | M |
| 176 to 183 cm | 83 to 88 cm | L | L | L | L | L |
| 183 to 192 cm | 87 to 94 cm | XL | XL | XL | XL | XL |
| 192 cm and up | 94 cm and up | XXL | — | — | — | XL |
Only the Racemax covers very short and very tall riders. The Primo runs to taller heights within its S to XL range, so its XL suits riders up to around 200 cm.
How to measure yourself
Height. Stand barefoot against 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 to the wall like a saddle and measure floor to spine.
The reliable check. 3T recommends matching stack and reach to a bike you ride well. If you are coming off an original Exploro, expect the current frames to feel longer and taller, so consider sizing down.
Race
The Racemax is the fast 700c aero gravel racer, the reference 3T fit, low and long but with a taller stack than the original Exploro. The Racemax² Italia is the newer, even sharper race version, marginally taller and longer per size. Both suit fast, smooth gravel and tarmac.
| Reach (mm) | XS | S | M | L | XL | XXL |
|---|---|---|---|---|---|---|
| Racemax | 353 | 364 | 374 | 382 | 390 | 401 |
| Racemax² Italia | — | 367 | 377 | 385 | 393 | — |
Racemax stack runs 522 (XS) to 634 (XXL) mm; Racemax² Italia 547 to 609 mm across S to XL.
Comfort and rough terrain
The Ultra² Italia is the most upright, long haul model, suspension fork and dropper ready with the highest stack and shortest reach. The Extrema Italia is the rough terrain specialist, taller and shorter than the Racemax for confidence off road with clearance up to 57 mm tyres.
| Reach (mm) | S | M | L | XL |
|---|---|---|---|---|
| Ultra² Italia | 360 | 368 | 376 | 384 |
| Extrema Italia | 358 | 368 | 376 | 384 |
Ultra² stack runs 560 to 620 mm, Extrema 547 to 610 mm across S to XL, so both sit noticeably taller than the Racemax at the same size.
Road all rounder
The Primo is the most road like of the range, the longest reach fit with height bands that skew taller, a versatile 700c or 650b all rounder rather than a dedicated racer.
| Frame size | S | M | L | XL |
|---|---|---|---|---|
| Stack (mm) | 532 | 561 | 590 | 619 |
| Reach (mm) | 366 | 378 | 390 | 402 |
| Rider height | 157 to 170 | 168 to 180 | 178 to 191 | 188 to 201 |
The Primo stack figures include the cable cover, which adds about 15 mm over the bare frame number 3T publishes.
What 3T riders find
The most useful takeaway is that the current range runs longer and taller than the original Exploro, adding a good chunk of stack and reach, so ex Exploro owners commonly size down to keep their old fit. The position overall is aggressive and road race like, with a steep seat angle and a low front relative to typical gravel bikes; the Extrema and Ultra exist precisely to add stack for riders who want a taller front. The aero shaping is genuinely fast on tarmac and smooth gravel, at the cost of a stiff chassis some find firm on skinny 700c tyres. On wheels, 3T matches the rolling radius so handling stays consistent whether you run 700c for speed or 650b for plush high volume comfort, so choose by terrain, not fit. The integrated cabling is clean but makes cockpit changes and travel more involved.
Between two sizes?
Go smaller for a racier reach, up for a taller, calmer front, and remember the whole range reads long, so ex Exploro riders in particular should lean down. Send us your height, inside leg and current bike's stack and reach and we will match it.
Shop 3T
- All 3T bikes including the Racemax, Ultra, Extrema and Primo
Aero gravel, dialled in: ask our concierge
With five models and a range that runs long, matching numbers beats guessing. Share your height, inside leg and current stack and reach with our concierge team and we will recommend the model and size. Talk to our concierge.
These sizes are guidance, not a fitting guarantee. Reach and stack are official 3T data and high confidence; the Primo stack includes the cable cover. Rider height ranges are 3T's own approximations, which the brand flags as indicative, so confirm against the specific bike you are buying.
