{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "bicycle-steerer-1-1-8",
 "name": "Bicycle fork steerer, 1 1/8 in (28.6 mm), threadless",
 "kind": "standard",
 "category": "Everyday mounts",
 "group": "Bicycle",
 "year": null,
 "question": "What diameter is a 1 1/8 inch steerer tube?",
 "tags": [
  "bicycle",
  "steerer",
  "headset",
  "stem",
  "top cap",
  "mount"
 ],
 "aliases": [
  "steerer diameter",
  "1 1/8 steerer mm",
  "28.6 steerer",
  "top cap bolt size",
  "star nut thread",
  "stem cap mount",
  "headset top cap mount"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/bicycle-steerer-1-1-8/",
 "sheet_txt": "https://xemstudio.com/objects/bicycle-steerer-1-1-8/sheet.txt",
 "sheet": {
  "basis": "White Industries star nut spec (1 1/8 in = 28.6 mm steerer, M6 × 1 thread, nominal Ø26.7 × 15) and Cane Creek top cap spec (S.H.I.S. stem clamp diameter 28.6)",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "The threadless 1 1/8 in steerer is Ø28.6 mm outside (1 1/8 in is 28.575 mm; the industry writes 28.6). The stem clamps around it, so a stem-cap or top-cap mount clamps the same Ø.",
   "The top cap bolt is M6 × 1 into a star nut pressed inside the steerer; White Industries gives the star nut a nominal Ø26.7 × 15. The star nut and top cap are not drawn (their fingers and caps differ by maker).",
   "File: the steerer as a Ø28.6 × 100 section, axis on X, plus a DXF of the circle (the outside only). Stem faceplate bolt patterns are not standardized between makers and are not drawn."
  ],
  "table": {
   "columns": [
    "feature",
    "mm",
    "from"
   ],
   "rows": [
    [
     "steerer outside",
     "Ø28.6 (1 1/8 in)",
     "White Industries, Cane Creek"
    ],
    [
     "top cap bolt",
     "M6 × 1",
     "White Industries"
    ],
    [
     "star nut (nominal)",
     "Ø26.7 × 15",
     "White Industries"
    ],
    [
     "stem clamp on the steerer",
     "28.6",
     "Cane Creek (S.H.I.S.)"
    ]
   ]
  }
 },
 "sheet_text": "Bicycle fork steerer, 1 1/8 in (28.6 mm), threadless — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/bicycle-steerer-1-1-8/  (CC BY 4.0)\nBasis: White Industries star nut spec (1 1/8 in = 28.6 mm steerer, M6 × 1 thread, nominal Ø26.7 × 15) and Cane Creek top cap spec (S.H.I.S. stem clamp diameter 28.6)\nCatalog version: 2026-10-20\n\nSizes: see table below\n- The threadless 1 1/8 in steerer is Ø28.6 mm outside (1 1/8 in is 28.575 mm; the industry writes 28.6). The stem clamps around it, so a stem-cap or top-cap mount clamps the same Ø.\n- The top cap bolt is M6 × 1 into a star nut pressed inside the steerer; White Industries gives the star nut a nominal Ø26.7 × 15. The star nut and top cap are not drawn (their fingers and caps differ by maker).\n- File: the steerer as a Ø28.6 × 100 section, axis on X, plus a DXF of the circle (the outside only). Stem faceplate bolt patterns are not standardized between makers and are not drawn.\n\nfeature  mm  from\nsteerer outside  Ø28.6 (1 1/8 in)  White Industries, Cane Creek\ntop cap bolt  M6 × 1  White Industries\nstar nut (nominal)  Ø26.7 × 15  White Industries\nstem clamp on the steerer  28.6  Cane Creek (S.H.I.S.)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- White Industries: Headset star nut: 1 1/8 in (28.6 mm) steerer, M6 × 1 thread, nominal Ø26.7 × 15 — web — manufacturer spec [verify license at link] — https://www.whiteind.com/product/headset-star-nut/\n- Cane Creek (listing by Velomine): Headset top cap 28.6 mm: S.H.I.S. stem clamp diameter 28.6, fits 1 1/8 in threadless — web — reference [verify license at link] — https://velomine.com/products/cane-creek-chroma-studio-headset-top-cap-28-6mm-silver\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/bicycle-steerer-1-1-8/index.json\nAPI: https://xemstudio.com/api/geometry?object=bicycle-steerer-1-1-8\n",
 "sources": [
  {
   "publisher": "White Industries",
   "title": "Headset star nut: 1 1/8 in (28.6 mm) steerer, M6 × 1 thread, nominal Ø26.7 × 15",
   "url": "https://www.whiteind.com/product/headset-star-nut/",
   "formats": [
    "web"
   ],
   "license": "manufacturer spec",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "Cane Creek (listing by Velomine)",
   "title": "Headset top cap 28.6 mm: S.H.I.S. stem clamp diameter 28.6, fits 1 1/8 in threadless",
   "url": "https://velomine.com/products/cane-creek-chroma-studio-headset-top-cap-28-6mm-silver",
   "formats": [
    "web"
   ],
   "license": "reference",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "bicycle-handlebar-diameters",
  "handlebar-clamp-rings",
  "socket-head-cap-screws-metric"
 ],
 "fits": [
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "socket-head-cap-screws-metric",
     "why": "M6 top cap bolt into the star nut"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "bicycle-handlebar-diameters",
     "why": "mount on the bar instead of the stem"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "steerer outside",
   "exact": "Ø28.6 (1 1/8 in)",
   "mates": "stem clamp, headset top cap",
   "fit": "clamp",
   "files": "steerer-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What diameter is a 1 1/8 steerer?",
   "a": "28.6 mm outside (1 1/8 in = 28.575 mm)."
  },
  {
   "q": "What thread is a bike top cap bolt?",
   "a": "M6 × 1 into the star nut, on 1 1/8 in steerers."
  },
  {
   "q": "Can a mount replace the headset top cap?",
   "a": "A top-cap mount takes the place of the cap under the same M6 × 1 bolt; it must still let the bolt preload the headset as the cap does."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "steerer-28.6-L100",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/bicycle-steerer-1-1-8/steerer-28.6-L100.step",
   "stl": "https://xemstudio.com/files/hardware/bicycle-steerer-1-1-8/steerer-28.6-L100.stl",
   "note": "1 1/8 in steerer section Ø28.6 × 100 long, axis on X: the outside of the steerer (the wall is not drawn); DXF = the Ø28.6 circle"
  }
 ],
 "markdown": "https://xemstudio.com/objects/bicycle-steerer-1-1-8/index.md"
}