{
  "name": "Bicycle Component Interface Standards Reference",
  "publisher": "CNC Bike Parts",
  "url": "https://cncbikeparts.com/reference/bike-part-standards/",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "attribution": "CNC Bike Parts, https://cncbikeparts.com/reference/bike-part-standards/",
  "lastChecked": "2026-09-27",
  "note": "Typical published dimensions. Verify against the component maker's drawing before cutting metal.",
  "tables": [
    {
      "id": "steerer",
      "title": "Steerer tubes and headsets",
      "columns": [
        "Standard",
        "Steerer outside diameter",
        "Notes"
      ],
      "rows": [
        [
          "1 in threadless",
          "25.4 mm",
          "Older road and touring frames"
        ],
        [
          "1 1/8 in",
          "28.6 mm",
          "The default for stems. Most common by a wide margin"
        ],
        [
          "1 1/4 in",
          "31.8 mm",
          "Uncommon, some road and gravel frames"
        ],
        [
          "1 1/2 in",
          "38.1 mm",
          "Lower bearing on tapered steerers, rarely a stem clamp"
        ],
        [
          "Tapered 1 1/8 to 1 1/2",
          "28.6 top, 38.1 bottom",
          "Stem still clamps the 28.6 mm section"
        ],
        [
          "Tapered 1 1/8 to 1 1/4",
          "28.6 top, 33.0 bottom",
          "Less common tapered variant"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, headset crib sheet",
          "url": "https://www.sheldonbrown.com/cribsheet-headsets.html"
        },
        {
          "name": "Wikipedia, Headset (bicycle part)",
          "url": "https://en.wikipedia.org/wiki/Headset_(bicycle_part)"
        }
      ]
    },
    {
      "id": "bars",
      "title": "Handlebar clamp and grip diameters",
      "columns": [
        "Diameter",
        "Where it is used",
        "Notes"
      ],
      "rows": [
        [
          "25.4 mm",
          "Stem clamp, older MTB and some flat bars",
          "Still current on some touring and city bars"
        ],
        [
          "26.0 mm",
          "Stem clamp, older road bars",
          "Largely superseded by 31.8 mm"
        ],
        [
          "31.8 mm",
          "Stem clamp, current road, gravel and MTB",
          "The default clamp bore to design for"
        ],
        [
          "35.0 mm",
          "Stem clamp, newer MTB",
          "Stiffer, allows thinner wall for the same strength"
        ],
        [
          "22.2 mm",
          "Grip and control area, flat bars",
          "Sets shifter, brake lever and grip bores"
        ],
        [
          "23.8 mm",
          "Tops and drops, road bars",
          "Sets lever clamp and bar tape area"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, handlebar crib sheet",
          "url": "https://www.sheldonbrown.com/cribsheet-handlebars.html"
        },
        {
          "name": "Wikipedia, Bicycle handlebar",
          "url": "https://en.wikipedia.org/wiki/Bicycle_handlebar"
        }
      ]
    },
    {
      "id": "seatpost",
      "title": "Seatposts, collars and saddle rails",
      "columns": [
        "Item",
        "Common sizes",
        "Notes"
      ],
      "rows": [
        [
          "Seatpost diameter",
          "27.2, 30.9, 31.6 mm",
          "The three that cover most modern frames. 27.2 mm for comfort, 30.9 and 31.6 mm for dropper posts"
        ],
        [
          "Other post diameters",
          "25.4, 26.8, 28.6, 31.8, 34.9 mm",
          "Older and speciality frames"
        ],
        [
          "Seat collar bore",
          "28.6, 30.0, 31.8, 34.9, 36.4 mm",
          "Sized to the frame seat tube outside diameter, roughly post plus 2.8 to 3.3 mm"
        ],
        [
          "Saddle rails, round",
          "7 mm",
          "Steel, titanium and alloy rails. The default clamp size"
        ],
        [
          "Saddle rails, oval",
          "7 x 9 mm",
          "Carbon rails. Needs a clamp designed for the oval section"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, seatpost sizes",
          "url": "https://www.sheldonbrown.com/seatpost-sizes.html"
        },
        {
          "name": "Wikipedia, Seatpost",
          "url": "https://en.wikipedia.org/wiki/Seatpost"
        }
      ]
    },
    {
      "id": "bb",
      "title": "Bottom bracket shells",
      "columns": [
        "Standard",
        "Shell bore or thread",
        "Shell widths"
      ],
      "rows": [
        [
          "BSA / ISO threaded",
          "1.37 in x 24 tpi",
          "68 mm road, 73 mm MTB. Drive side cup is left hand thread"
        ],
        [
          "Italian threaded",
          "36 mm x 24 tpi",
          "70 mm. Both cups right hand thread"
        ],
        [
          "T47",
          "47 mm x 1.0 mm thread",
          "68, 77, 85.5 and 86.5 mm"
        ],
        [
          "BB86 / BB92",
          "41 mm bore, press fit",
          "86.5 mm road, 91.5 mm MTB"
        ],
        [
          "BB30",
          "42 mm bore, press fit",
          "68 mm road, 73 mm MTB"
        ],
        [
          "PF30",
          "46 mm bore, press fit",
          "68 mm road, 73 mm MTB"
        ],
        [
          "BB386EVO",
          "46 mm bore, press fit",
          "86.5 mm"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Park Tool, bottom bracket standards and terminology",
          "url": "https://www.parktool.com/en-us/blog/repair-help/bottom-bracket-standards-and-terminology"
        },
        {
          "name": "Sheldon Brown, bottom bracket sizes",
          "url": "https://www.sheldonbrown.com/bbsize.html"
        },
        {
          "name": "Wikipedia, Bottom bracket",
          "url": "https://en.wikipedia.org/wiki/Bottom_bracket"
        }
      ]
    },
    {
      "id": "spindle",
      "title": "Crank spindle interfaces",
      "columns": [
        "Interface",
        "Spindle",
        "Notes"
      ],
      "rows": [
        [
          "Square taper",
          "2 degrees per side",
          "JIS and ISO variants differ in taper length, not angle"
        ],
        [
          "Octalink V1",
          "22 mm, 8 splines",
          "Shimano. V1 and V2 differ in spline depth and are not interchangeable"
        ],
        [
          "ISIS Drive",
          "22 mm, 10 splines",
          "Open standard, several makers"
        ],
        [
          "Hollowtech II",
          "24 mm",
          "Shimano external bearing. Widely copied"
        ],
        [
          "SRAM GXP",
          "24 mm drive, 22 mm non-drive",
          "Stepped spindle, non-drive bearing takes the smaller diameter"
        ],
        [
          "SRAM DUB",
          "28.99 mm",
          "Single spindle diameter across shell standards"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, bottom bracket tapers and splines",
          "url": "https://www.sheldonbrown.com/bbtaper.html"
        },
        {
          "name": "Park Tool, bottom bracket standards and terminology",
          "url": "https://www.parktool.com/en-us/blog/repair-help/bottom-bracket-standards-and-terminology"
        },
        {
          "name": "Wikipedia, Bottom bracket",
          "url": "https://en.wikipedia.org/wiki/Bottom_bracket"
        }
      ]
    },
    {
      "id": "bcd",
      "title": "Chainring bolt circles and mounts",
      "columns": [
        "Pattern",
        "BCD",
        "Notes"
      ],
      "rows": [
        [
          "Road 5-bolt standard",
          "130 mm",
          "Older Shimano and compatible"
        ],
        [
          "Road 5-bolt compact",
          "110 mm",
          "The long running compact road pattern"
        ],
        [
          "Campagnolo 5-bolt",
          "135 mm",
          "Campagnolo specific"
        ],
        [
          "Road 4-bolt",
          "110 mm asymmetric",
          "Shimano 11 and 12 speed. Bolt spacing is not equal"
        ],
        [
          "MTB 4-bolt outer",
          "104 mm",
          "The long standing MTB pattern"
        ],
        [
          "MTB 4-bolt inner",
          "64 mm",
          "Granny ring position on triples"
        ],
        [
          "Shimano MTB 4-bolt",
          "96 mm",
          "Symmetric and asymmetric versions exist"
        ],
        [
          "SRAM 4-bolt",
          "94 mm",
          "SRAM specific MTB pattern"
        ],
        [
          "Direct mount",
          "No bolt circle",
          "SRAM 3-bolt and Shimano direct mount. Proprietary interface geometry, take it from the crank maker"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, chainring bolt circle crib sheet",
          "url": "https://www.sheldonbrown.com/cribsheet-bcd.html"
        },
        {
          "name": "Wikipedia, Crankset",
          "url": "https://en.wikipedia.org/wiki/Crankset"
        }
      ]
    },
    {
      "id": "chainline",
      "title": "Chainline",
      "columns": [
        "Setup",
        "Typical chainline",
        "Notes"
      ],
      "rows": [
        [
          "Road double",
          "About 43.5 mm",
          "Measured to the midpoint between the two rings"
        ],
        [
          "MTB 1x, non-Boost",
          "About 49 mm",
          "Matches 142 mm rear spacing"
        ],
        [
          "MTB 1x, Boost",
          "About 52 mm",
          "Matches 148 mm rear spacing. Boost specific rings exist for this reason"
        ],
        [
          "MTB 1x, Super Boost",
          "About 56 mm",
          "Matches 157 mm rear spacing"
        ]
      ],
      "note": "Chainline figures vary a little by drivetrain maker. Confirm against the groupset specification for the build.",
      "sources": [
        {
          "name": "Sheldon Brown, chainline",
          "url": "https://www.sheldonbrown.com/chainline.html"
        },
        {
          "name": "Wikipedia, Chainline",
          "url": "https://en.wikipedia.org/wiki/Chainline"
        }
      ]
    },
    {
      "id": "hubs",
      "title": "Hub spacing and axle standards",
      "columns": [
        "Position",
        "Standard",
        "Notes"
      ],
      "rows": [
        [
          "Front, quick release",
          "100 mm QR",
          "Rim brake and older disc"
        ],
        [
          "Front, road disc",
          "100 x 12 mm",
          "Current road and gravel disc"
        ],
        [
          "Front, MTB",
          "100 x 15 mm",
          "Pre-Boost MTB thru axle"
        ],
        [
          "Front, Boost",
          "110 x 15 mm",
          "Current MTB standard"
        ],
        [
          "Rear, road rim brake",
          "130 mm QR",
          "Legacy road"
        ],
        [
          "Rear, MTB quick release",
          "135 mm QR",
          "Legacy MTB"
        ],
        [
          "Rear, road disc",
          "142 x 12 mm",
          "Current road, gravel and older MTB"
        ],
        [
          "Rear, Boost",
          "148 x 12 mm",
          "Current MTB standard"
        ],
        [
          "Rear, Super Boost",
          "157 x 12 mm",
          "Some enduro and plus tyre frames"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, hub spacing crib sheet",
          "url": "https://www.sheldonbrown.com/cribsheet-spacing.html"
        },
        {
          "name": "Wikipedia, Thru-axle",
          "url": "https://en.wikipedia.org/wiki/Thru-axle"
        },
        {
          "name": "Wikipedia, Bicycle wheel",
          "url": "https://en.wikipedia.org/wiki/Bicycle_wheel"
        }
      ]
    },
    {
      "id": "freehub",
      "title": "Freehub body standards",
      "columns": [
        "Standard",
        "Used by",
        "Notes"
      ],
      "rows": [
        [
          "Shimano HG",
          "Shimano and compatible",
          "The long standing spline. Road 11 speed uses a longer body than MTB"
        ],
        [
          "SRAM XD",
          "SRAM MTB",
          "Threaded cassette interface, allows a 10 tooth smallest cog"
        ],
        [
          "SRAM XDR",
          "SRAM road",
          "XD geometry, body 1.85 mm longer"
        ],
        [
          "Shimano Micro Spline",
          "Shimano 12 speed MTB",
          "Also allows a 10 tooth cog"
        ],
        [
          "Campagnolo N3W",
          "Campagnolo",
          "Adapter allows older Campagnolo cassettes"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, cassettes and freehubs",
          "url": "https://www.sheldonbrown.com/k7.html"
        },
        {
          "name": "Wikipedia, Freehub",
          "url": "https://en.wikipedia.org/wiki/Freehub"
        }
      ]
    },
    {
      "id": "brakes",
      "title": "Disc brake mounts and rotors",
      "columns": [
        "Interface",
        "Specification",
        "Notes"
      ],
      "rows": [
        [
          "Rotor, 6-bolt ISO",
          "44 mm BCD, six M5",
          "The common rotor mount. Bolts usually torque to 4 to 6 Nm"
        ],
        [
          "Rotor, Center Lock",
          "Splined, lockring",
          "Shimano interface, also used by others"
        ],
        [
          "Caliper, IS",
          "Two M6, perpendicular to the mount",
          "Older frames and forks, needs an adapter for most calipers"
        ],
        [
          "Caliper, Post Mount",
          "Two M6, 74 mm spacing",
          "The common MTB mount. Adapters set the rotor size"
        ],
        [
          "Caliper, Flat Mount",
          "Two M5 from below",
          "Road and gravel disc"
        ],
        [
          "Rotor diameters",
          "140, 160, 180, 203 mm",
          "The adapter converts between the frame mount size and the rotor size"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Wikipedia, Bicycle brake",
          "url": "https://en.wikipedia.org/wiki/Bicycle_brake"
        },
        {
          "name": "Wikipedia, Disc brake",
          "url": "https://en.wikipedia.org/wiki/Disc_brake"
        }
      ]
    },
    {
      "id": "threads",
      "title": "Threads and fasteners",
      "columns": [
        "Location",
        "Thread",
        "Notes"
      ],
      "rows": [
        [
          "Pedal to crank",
          "9/16 in x 20 tpi",
          "Right hand thread drive side, left hand thread non-drive side. One-piece cranks use 1/2 in x 20 tpi"
        ],
        [
          "Derailleur to hanger",
          "M10 x 1.0",
          "Standard on modern hangers including UDH"
        ],
        [
          "Bottle cage",
          "Two M5 at 64 mm",
          "The universal accessory mount pattern"
        ],
        [
          "Disc rotor bolts",
          "M5",
          "Six per rotor on the ISO pattern"
        ],
        [
          "Post mount caliper",
          "M6",
          "Two bolts at 74 mm"
        ],
        [
          "Stem and faceplate",
          "M5",
          "M6 on some single bolt steerer clamps"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Wikipedia, Bicycle pedal",
          "url": "https://en.wikipedia.org/wiki/Bicycle_pedal"
        },
        {
          "name": "Wikipedia, Bottle cage",
          "url": "https://en.wikipedia.org/wiki/Bottle_cage"
        },
        {
          "name": "Wikipedia, Derailleur hanger",
          "url": "https://en.wikipedia.org/wiki/Derailleur_hanger"
        }
      ]
    },
    {
      "id": "bearings",
      "title": "Common cartridge bearings",
      "columns": [
        "Bearing",
        "Bore x OD x width",
        "Typically used in"
      ],
      "rows": [
        [
          "688",
          "8 x 16 x 5 mm",
          "Derailleur pulleys, small pivots"
        ],
        [
          "6901",
          "12 x 24 x 6 mm",
          "Pivots, small hubs"
        ],
        [
          "6001",
          "12 x 28 x 8 mm",
          "Pivots, suspension links"
        ],
        [
          "6802",
          "15 x 24 x 5 mm",
          "Light hub shells, pulleys"
        ],
        [
          "6902",
          "15 x 28 x 7 mm",
          "The most common hub bearing"
        ],
        [
          "6903",
          "17 x 30 x 7 mm",
          "Rear hubs, freehub bodies"
        ],
        [
          "6805",
          "25 x 37 x 7 mm",
          "Bottom brackets, large bores"
        ],
        [
          "6806",
          "30 x 42 x 7 mm",
          "BB30 and large hub shells"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "SKF product data, deep groove ball bearing 6902",
          "url": "https://www.skf.com/group/products/rolling-bearings/ball-bearings/deep-groove-ball-bearings/productid-6902"
        },
        {
          "name": "SKF product data, deep groove ball bearing 6805",
          "url": "https://www.skf.com/group/products/rolling-bearings/ball-bearings/deep-groove-ball-bearings/productid-6805"
        },
        {
          "name": "ISO 15, boundary dimensions for radial rolling bearings",
          "url": null
        }
      ]
    },
    {
      "id": "spokes",
      "title": "Spokes and spoke holes",
      "columns": [
        "Item",
        "Size",
        "Notes"
      ],
      "rows": [
        [
          "Spoke, 14 gauge",
          "2.0 mm",
          "The common straight gauge spoke"
        ],
        [
          "Spoke, 15 gauge",
          "1.8 mm",
          "Butted section of a double butted spoke"
        ],
        [
          "Spoke, 13 gauge",
          "2.34 mm",
          "Heavy duty, cargo and tandem"
        ],
        [
          "Spoke hole in flange",
          "About 2.5 mm",
          "For a 2.0 mm spoke. Angled or counterbored so the elbow seats without bending"
        ],
        [
          "Straight pull",
          "No elbow",
          "Different flange geometry entirely, hole is a slot or a stepped bore"
        ]
      ],
      "note": null,
      "sources": [
        {
          "name": "Sheldon Brown, glossary Sp to Ss (spoke gauge)",
          "url": "https://www.sheldonbrown.com/gloss_sp-ss.html"
        },
        {
          "name": "Wikipedia, Spoke",
          "url": "https://en.wikipedia.org/wiki/Spoke"
        }
      ]
    }
  ]
}