27.2 mm seatpost (27.2 mm)
Which frames use a 27.2 mm seatpost, and how it differs from the sizes either side of it.
Published dimensions
| Diameter | 27.2 mm |
|---|---|
| Designation | 27.2 mm |
| Typical frames | the de facto standard on modern road and gravel frames, and many hardtail and lightweight full-suspension frames |
Used on: the de facto standard on modern road and gravel frames, and many hardtail and lightweight full-suspension frames.
27.2 mm became the road standard because a thin-walled 1 1/8 in (28.6 mm) outside-diameter seat tube leaves a 27.2 mm bore. Its smaller diameter also flexes slightly for comfort, which is why endurance and gravel frames favour it. A frame cut for 27.2 mm will not hold a 30.9 or 31.6 mm post without a shim.
Frames and related seatpost sizes
Seatpost on a Trek Emonda SLR (2024 on)27.2 mmSeatpost on a Specialized Tarmac SL8 (2024 on)27.2 mmSeatpost on a Canyon Ultimate CF (2020 on)27.2 mm30.6 mm seatpost30.6 mm30.9 mm seatpost30.9 mmBSA bottom bracket shellthe frame's other threaded interface
SOURCES: Sheldon Brown, Seatpost Size Database · BikeRadar, Bike seatposts explained: diameters, materials, lengths