# Reverse (anti-) Ackermann

> Why do some race cars use anti-Ackermann steering?

- 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/anti-ackermann/ · JSON: https://xemstudio.com/api/geometry?object=anti-ackermann · Plain text: https://xemstudio.com/objects/anti-ackermann/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

- At high cornering speed the outside front tyre carries more load and wants a larger slip angle, so pure Ackermann is not ideal. Some racing cars use reverse Ackermann to offset the slip-angle difference, which cuts tyre temperatures in fast corners but hurts low-speed performance (Wikipedia).
- On RC cars, less Ackermann gives smoother turn-in, more mid-corner stability and more even front tyre wear (CompetitionX).
- 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.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Reverse Ackermann use | high-speed corners; worse at low speed | Wikipedia |
| Less Ackermann (RC) | smoother turn-in, more stable, even tyre wear | CompetitionX |

## Where the files are

- Wikipedia: [Ackermann steering geometry](https://en.wikipedia.org/wiki/Ackermann_steering_geometry) — web — Publisher's page; dimensions are facts
- CompetitionX: [RC Ackermann Steering Explained](https://www.competitionx.com/?p=14) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/anti-ackermann/index.json · license: https://xemstudio.com/files/hardware/anti-ackermann/LICENSE.md

- anti-ackermann-geometry: [STEP](https://xemstudio.com/files/hardware/anti-ackermann/anti-ackermann-geometry.step) · [STL](https://xemstudio.com/files/hardware/anti-ackermann/anti-ackermann-geometry.stl) — Ackermann demo: inner wheel 30°, outer wheel per the Ackermann relation for wheelbase 260, track 190 (illustrative layout)

## Questions

**Is parallel steer the same as anti-Ackermann?**

Parallel steer sits between the two; the sources describe reduced and reverse Ackermann for high-speed cornering.

## Fits with

- [Camber angle](https://xemstudio.com/objects/camber/)
- [Caster angle](https://xemstudio.com/objects/caster/)
- [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/)