{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "scrub-radius",
 "name": "Scrub radius",
 "kind": "standard",
 "category": "Car design",
 "group": "Suspension geometry",
 "year": null,
 "question": "What is scrub radius and is positive or negative better?",
 "tags": [
  "vehicle design",
  "suspension geometry",
  "rc design",
  "aerodynamics"
 ],
 "aliases": [
  "scrub radius",
  "negative scrub radius",
  "positive scrub radius",
  "wheel offset scrub",
  "steering offset",
  "kingpin offset",
  "scrub radius torque steer",
  "zero scrub radius",
  "scrub radius calculation"
 ],
 "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/scrub-radius/",
 "sheet_txt": "https://xemstudio.com/objects/scrub-radius/sheet.txt",
 "sheet": {
  "basis": "Design rules and figures from the cited sources; example geometry by Xem Studio",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Scrub radius is the front-view distance at the ground between the steering axis and the contact-patch centre (Wikipedia). Positive scrub lowers parking effort and adds road feel; negative scrub resists pull under uneven braking or a flat tyre and reduces torque steer.",
   "Zero scrub causes the tyre to 'squirm', wearing it and reducing stability (Wikipedia; H&R). A small radius improves steering feel; a large one increases torque steer (HPA).",
   "Wheel offset is the easiest way to change it; more aggressive offset increases scrub radius (HPA; H&R).",
   "The file is a reference example built by Xem Studio from the numbers above (Reference 1/10 touring car: wheelbase 260 mm (AARCMCC ISTC 250-270), track 190 mm (EFRA width without body), 50 mm = EFRA rim limit.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle."
  ],
  "table": {
   "columns": [
    "parameter",
    "value or range",
    "source"
   ],
   "rows": [
    [
     "Older cars",
     "about 100 mm (4 in) positive",
     "Wikipedia"
    ],
    [
     "MacPherson strut",
     "usually negative",
     "Wikipedia"
    ],
    [
     "SLA double wishbone",
     "usually positive",
     "Wikipedia"
    ],
    [
     "FSAE example",
     "27.768 mm front, 56.529 mm rear",
     "Univ. of Utah FSAE"
    ]
   ]
  }
 },
 "sheet_text": "Scrub radius — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/scrub-radius/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)\nBasis: Design rules and figures from the cited sources; example geometry by Xem Studio\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Scrub radius is the front-view distance at the ground between the steering axis and the contact-patch centre (Wikipedia). Positive scrub lowers parking effort and adds road feel; negative scrub resists pull under uneven braking or a flat tyre and reduces torque steer.\n- Zero scrub causes the tyre to 'squirm', wearing it and reducing stability (Wikipedia; H&R). A small radius improves steering feel; a large one increases torque steer (HPA).\n- Wheel offset is the easiest way to change it; more aggressive offset increases scrub radius (HPA; H&R).\n- The file is a reference example built by Xem Studio from the numbers above (Reference 1/10 touring car: wheelbase 260 mm (AARCMCC ISTC 250-270), track 190 mm (EFRA width without body), 50 mm = EFRA rim limit.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.\n\nparameter  value or range  source\nOlder cars  about 100 mm (4 in) positive  Wikipedia\nMacPherson strut  usually negative  Wikipedia\nSLA double wishbone  usually positive  Wikipedia\nFSAE example  27.768 mm front, 56.529 mm rear  Univ. of Utah FSAE\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Scrub radius — web — Publisher's page; dimensions are facts — https://en.wikipedia.org/wiki/Scrub_radius\n- H&R Springs (Roger Jackman): Scrub radius — web — Publisher's page; dimensions are facts — https://hrsprings.com/technical/scrub-radius\n- High Performance Academy: Wheel alignment terminology: king pin inclination and scrub radius — web — Publisher's page; dimensions are facts — https://www.hpacademy.com/courses/motorsport-wheel-alignment-fundamentals/wheel-alignment-terminology-king-pin-inclination-and-scrub-radius\n- University of Utah, Mechanical Engineering: Formula SAE Suspension System (senior design) — web — Publisher's page; dimensions are facts — https://mech.utah.edu/wp-content/uploads/2024/12/5-Formula-SAE-Suspension.pdf\n\nFree files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/scrub-radius/index.json\nAPI: https://xemstudio.com/api/geometry?object=scrub-radius\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Scrub radius",
   "url": "https://en.wikipedia.org/wiki/Scrub_radius",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "H&R Springs (Roger Jackman)",
   "title": "Scrub radius",
   "url": "https://hrsprings.com/technical/scrub-radius",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "High Performance Academy",
   "title": "Wheel alignment terminology: king pin inclination and scrub radius",
   "url": "https://www.hpacademy.com/courses/motorsport-wheel-alignment-fundamentals/wheel-alignment-terminology-king-pin-inclination-and-scrub-radius",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "University of Utah, Mechanical Engineering",
   "title": "Formula SAE Suspension System (senior design)",
   "url": "https://mech.utah.edu/wp-content/uploads/2024/12/5-Formula-SAE-Suspension.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "camber",
  "caster",
  "kick-up",
  "toe-front",
  "toe-rear",
  "ackermann"
 ],
 "fits": [],
 "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": [],
 "faq": [
  {
   "q": "Why do ABS-era cars use negative scrub?",
   "a": "It counters uneven braking, keeps steering straight with a flat tyre and reduces torque steer (Wikipedia)."
  }
 ],
 "files_license": {
  "name": "Xem Studio Design License",
  "holder": "Xem Studio",
  "url": "https://xemstudio.com/license/",
  "note": "Xem Studio's own design: free to use, print, modify and sell things made from it; not to be republished or redistributed as files."
 },
 "offers": [
  {
   "file": "scrub-radius-geometry",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "Xem Studio Design License",
   "step": "https://xemstudio.com/files/hardware/scrub-radius/scrub-radius-geometry.step",
   "stl": "https://xemstudio.com/files/hardware/scrub-radius/scrub-radius-geometry.stl",
   "note": "kpi demo: front axle, track 190 mm, Ø50 tyres, 2.35° (illustrative layout)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/scrub-radius/index.md"
}