Sheldon Brown's Bicycle Headset Dimension Crib Sheet
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Threaded Headsets/Steerers
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|---|---|---|---|---|---|---|
| Standard | Frame Cup Outside Diameter |
Crown race Inside diameter |
Steerer O.D in mm | Threads Per inch |
Stem diameter, Steerer I.D. |
Notes |
| 1" J.I.S. |
30.0 mm | 27.0 mm | 25.4 mm | 24 | 22.2 mm (7/8") | Older or lower-quality bicycles from Asia. Can be milled to ISO standard. ISO and other 30.2 mm O.D.cups are a very tight fit into the head tube; best mill it to avoid damage. |
| 1" Raleigh |
30.0 mm | 27.0 mm | 25.4 mm | 26 | 22.2 mm (7/8") | Proprietary size used on Raleighs made in Nottingham, England. ISO and other 30.2 mm O.D, frame cups are a very tight fit into the head tube; best mill to avoid damage. |
| 1" ISO Standard |
30.2 mm | 26.4 mm |
25.4 mm |
24 | 22.2 mm (7/8") | This is the standard 1" size. |
| 1" Professional/ Campagnolo |
30.2 mm | 26.4 mm |
25.4 mm | 24 | 22.2 mm (7/8") | Obsolete. Threads are cut at 55 degrees, but an ISO headset can be used. |
| 1" Italian | 30.2 mm | 26.5 mm, 27.0 mm |
25.4 mm | 24 | 22.2 mm (7/8") | Obsolete. Threads are cut at 55 degrees, but an ISO or J.I.S. top headset can be used. Fork can be milled to ISO. |
| French | 30.2 mm | 26.5 mm, 27.0 mm |
25.0 mm | 25.4 (1 mm) |
22.0 mm | Obsolete. French steerers usually have a flat filed on the back, rather than a grooved keyway as with other threaded systems. The bottom headset parts wear faster; you can replace them with ISO parts and use the old top headset. |
| East German (DDR) | 30.6 mm | 26.8 mm (1 1/8") |
26 mm | 26 | 22.0 mm | Very similar to or the same as Austrian. 0.2 mm discrepancy may result from measuring the I.D. of the head tube (press fit). See page on German site. |
| Austrian |
30.8 mm | 26.7 mm | 26 mm | 25.4 (1 mm) |
22.0 mm | These are found on bicycles sold by Sears, made by Steyr in Austria. Higher quality Austrian bikes use English/ISO. |
| BMX/ O.P.C. bikes | 32.6 mm (varies) |
26.4 mm (varies) | 25.4 mm | 24 | 21.15 mm (.833") |
Used mainly on bicycles with one-piece cranks, also some early mountain bikes. |
| French Tandem | Let us know, if you do! | 28 mm | Let us now, if you do! | 25.4 (1 mm) |
22.0 mm | Obsolete and rare. |
| 1 1/8" | 34.0 mm | 30.0 mm | 28.6 mm | 26 | 25.4 mm (1") | "Oversized" (This size is more often used for threadless systems.) |
| Moulton | 30.2 mm top, 36.4 bottom |
33.0 mm | 25.4 mm | 24 | 22.2 mm (7/8") |
Moulton Mark III and earlier. Top headset is standard ISO. |
| 1 1/4" | 37.0 mm | 33.0 mm | 31.8 mm | 26 | 28.6 mm (1 1/8") | Mainly used on tandems |
| Threadless Headsets/Steerers | |||||
|---|---|---|---|---|---|
| Stem I.D., Steerer O.D. |
SHIS term |
Frame Cup/ Cartridge Outside Diameter |
Crown race Inside diameter |
Notes | |
| 21.15 mm (0.833") |
EC32 | 32.7 mm | 26.4 mm | Used mainly on bicycles with one-piece cranks. BMX/O.P.C | |
| 1" (25.4 mm) |
IS38 | 38.0 mm | 26.4 mm | Slip fit, 36° angular contact at bottom of bore. | EC30 | 30.2 mm | 26.4 mm | This is the ISO standard 1" size. |
| 1 1/8" (28.6 mm) |
EC34 | 34.0 mm | 30.0 mm | Most newer mountain bikes with external cups use this size. | |
| IS41 | 41.0 mm | Integrated, angular contact, slip fit. | |||
| ZS41 | 41.3 mm | Low profile, press fit. May have cartridge or cup-and-cone bearings. | |||
| 41.6 mm | Integrated, angular contact. Obsolete. | ||||
| IS42 | 41.8 mm | Integrated angular contact; Campagnolo Hiddenset | |||
| 41.9-42.0 mm | Microtech integrated, press fit, square-bottomed recesses. Obsolete | ||||
| ZS44 | 44.0 mm | Retainer/loose balls or cartridge, which is slip fit into pressed cup | |||
| 44.0 mm | Integrated, 36° angular contact. Obsolete | ||||
| IS47 | 47.0 mm | Integrated lower only, slip fit. | |||
| Various | 52-56mm | Use crown race reducer | |||
| 1 1/4" (31.8 mm) |
EC37 | 37.0 mm | 33.0 mm | Mainly used on tandems | |
| 1.5" (38.1 mm) |
EC49, ZS49 |
49.7 mm | 39.8 mm | OnePointFive standard for downhill and freeride applications. Press fit | |
| 52 mm (2.05") |
IS52 | 52 mm | 39.8mm | Integrated lower headset. Slip fit. | |
| 55 mm (2.165) |
ZS55/40 | 55 mm | 39.8mm | Internal, press fit. | |
| 56 mm (2.21") |
EC56, ZS56 |
56 mm | 39.8mm | Internal or external, press fit. | |
| Handlebar dimensions | ||||
|---|---|---|---|---|
| Stem Clamp Size |
Grip Area Size |
Application | ||
| 22.2 mm | 7/8" | 22.2 mm | 7/8" | Steel bars. Mainly BMX, older Mountain bike bars. |
| 23.8 mm | 15/16" | 22.2 mm | 7/8" | Obsolete British size for steel handlebars, common on older 3-speeds. This size was also used for older British steel drop bars. |
| 25 mm | 23.5 mm | Obsolete French size. | ||
| 25.4 mm | 1" | 22.2 mm | 7/8" | Standard I.S.O. size, used on the vast majority of newer bicycles with upright handlebars. This size was formerly common for steel drop bars. |
| 25.4 mm | 1" | 23.8 mm | 15/16" | Standard I.S.O. size, used on most bicycles with drop handlebars. Also used on older British aluminium upright handlebars. |
| 25.8 mm | 23.8 mm | 15/16" | Unofficial in-between size used by some Italian handlebar makers for handlebars designed to be usable in either ISO (25.4) or Italian (26.0) size stems. | |
| 26.0 mm | 23.8 mm | 15/16" | Italian standard for drop bars, other bars made to fit Italian stems and some high-end aftermarket drop bars. This is sometimes incorrectly called "road" size. |
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| 26.4 mm | 23.8 mm | 15/16" | Older Cinelli and Cinelli copies. Cinelli changed over to 26.0 mm in 1998. | |
| 27 mm | 23.8 mm | 15/16" | Titan (obsolete). | |
| 31.8 mm | 1 1/4" | 23.8 mm | 15/16" | Road oversized. |
Last Updated: by Harriet Fell