Bicycle handlebar diameters: 22.2, 23.8, 25.4, 26.0, 31.8 and 35.0 mm — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/bicycle-handlebar-diameters/ (CC BY 4.0) Basis: Clamp and grip diameters from Sheldon Brown's handlebar crib sheet and BikeGremlin's handlebar standards; current popularity of 31.8 and 35 from Bikepacking.com's stem-clamp survey Catalog version: 2026-10-20 Sizes: see table below - A bar has two diameters that matter: the clamp section in the middle (where the stem holds it) and the grip section out to the ends (where grips, brake levers, shifters, lights and phone mounts go). - Flat and riser bars are Ø22.2 (7/8 in) at the grips whatever their clamp size; drop bars are Ø23.8 (15/16 in) at the hoods and drops. - Clamp sizes in use: 22.2, 23.8, 25.4 (the ISO size), 26.0 (Italian drop bars), 31.8 (oversized, the most common today) and 35.0 (modern trail bars). Older bars also came in 25.0 (French), 25.8, 26.4 and 27.0, not drawn here. - Files: each diameter as a Ø × 100 mm section, axis on X, plus a DXF of the circle. They are the outside of the bar only: wall thickness differs between bars and is not part of the interface, so the inside is not drawn. - Most bars swell or taper between the clamp and the grip section; measure where your part will sit. A clamp drawn to the bar Ø closes onto the bar: see handlebar-clamp-rings. clamp or section Ø (mm) inch where it is used from Ø22.2 7/8 in BMX bars, older mountain bikes and small children's bikes; also the flat-bar grip, brake-lever and shifter section Sheldon Brown, BikeGremlin Ø23.8 15/16 in the drop-bar grip, brake-lever and bar-end section; also an older British clamp size on 3-speeds Sheldon Brown, BikeGremlin Ø25.4 1 in the ISO clamp size: most upright bars, older drop bars Sheldon Brown, BikeGremlin, Bikepacking.com Ø26.0 — the Italian drop-bar clamp size Sheldon Brown, BikeGremlin Ø31.8 1 1/4 in the oversized clamp: the most common clamp size today on road, gravel and mountain bars Sheldon Brown, BikeGremlin, Bikepacking.com Ø35.0 1 3/8 in the 35 mm clamp on modern mountain (trail) bars Sheldon Brown, BikeGremlin, Bikepacking.com grip section, flat bars Ø22.2 (7/8 in) with clamp 22.2, 25.4, 31.8 or 35.0 Sheldon Brown, BikeGremlin grip section, drop bars Ø23.8 (15/16 in) with clamp 23.8, 25.4, 26.0 or 31.8 Sheldon Brown, BikeGremlin Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - Sheldon Brown (Harris Cyclery): Handlebar and stem dimension crib sheet: clamp and grip diameters — web — reference [verify license at link] — https://www.sheldonbrown.com/cribsheet-handlebars.html - BikeGremlin: Bicycle handlebar dimension standards: clamp 22.2 to 35 mm, grip 22.2 / 23.8 mm — web — reference [verify license at link] — https://bike.bikegremlin.com/3784/bicycle-handlebar-dimension-standards/ - Bikepacking.com: Stem clamp diameters: a brief history and survey results (31.8 most common, 35 on trail bikes) — web — reference [verify license at link] — https://bikepacking.com/gear/stem-clamp-diameters/ Free files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/bicycle-handlebar-diameters/index.json API: https://xemstudio.com/api/geometry?object=bicycle-handlebar-diameters