# Caster angle

> What is caster and why do race cars and RC cars run so much of it?

- Category: Car design › Suspension geometry
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/caster/ · JSON: https://xemstudio.com/api/geometry?object=caster · Plain text: https://xemstudio.com/objects/caster/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Caster is the side-view tilt of the steering axis. With positive caster the axis meets the road ahead of the contact patch, so the wheel trails and self-centres, improving directional stability (Wikipedia).
- More caster gives straight-line stability and camber gain when steering but heavier, less responsive steering (Wikipedia; Formula1-Dictionary). On RC cars, higher caster gives more stability and less off-power corner-entry steering (Tekno).
- Road cars commonly run over 7 deg with radial tyres; some F1 cars exceed 10 deg; RC buggies stack kick-up and caster-block angles to well over 20 deg.
- The file is a reference example built by Xem Studio from the numbers above (Reference 1/10 off-road: track 250 mm and 90 mm wheel+tyre (EFRA maxima); wheelbase illustrative.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Road cars (radial tyres) | over 7 deg common | Wikipedia |
| F1 | at least a few deg; some over 10 deg | Formula1-Dictionary |
| FSAE example | +2.923 deg front, mechanical trail 11.667 mm | Univ. of Utah FSAE |
| RC total caster example | 11 deg kick-up + 0.5 deg insert + 15 deg block = 26.5 deg | Tekno setup guide |
| RC caster blocks (C-hub) | 21, 18, 15 deg options | Adrenaline RC |

## Where the files are

- Wikipedia: [Caster angle](https://en.wikipedia.org/wiki/Caster_angle) — web — Publisher's page; dimensions are facts
- Formula1-Dictionary: [Castor angle](https://formula1-dictionary.net/castor_angle.html) — web — Publisher's page; dimensions are facts
- University of Utah, Mechanical Engineering: [Formula SAE Suspension System (senior design)](https://mech.utah.edu/wp-content/uploads/2024/12/5-Formula-SAE-Suspension.pdf) — web — Publisher's page; dimensions are facts
- Tekno RC: [Tekno RC Setup Guide](https://teknoforums.com/misc/Tekno-RC-Setup-Guide.pdf) — web — Publisher's page; dimensions are facts
- Adrenaline RC Racing: [Mastering Caster & Kick-Up for Better Offroad RC Racing Performance](https://www.adrenalinercracing.com/blogs/news/mastering-caster-kick-up-for-better-offroad-rc-racing-performance) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/caster/index.json · license: https://xemstudio.com/files/hardware/caster/LICENSE.md

- caster-geometry: [STEP](https://xemstudio.com/files/hardware/caster/caster-geometry.step) · [STL](https://xemstudio.com/files/hardware/caster/caster-geometry.stl) — Caster demo: steering axis tilted back 26.5°, wheelbase 260 mm, Ø90 tyres (illustrative layout)

## Questions

**Why does caster add camber when steering?**

Tilting the steering axis back makes the outside wheel lean in as it steers; racers use large caster for this camber gain (Wikipedia).

## Fits with

- [Camber angle](https://xemstudio.com/objects/camber/)
- [Front kick-up (RC)](https://xemstudio.com/objects/kick-up/)
- [Front toe (toe-in / toe-out)](https://xemstudio.com/objects/toe-front/)
- [Rear toe-in](https://xemstudio.com/objects/toe-rear/)
- [Ackermann steering geometry](https://xemstudio.com/objects/ackermann/)
- [Reverse (anti-) Ackermann](https://xemstudio.com/objects/anti-ackermann/)