# Semi-trailing arm suspension

> What is a semi-trailing arm?

- 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/semi-trailing-arm/ · JSON: https://xemstudio.com/api/geometry?object=semi-trailing-arm · Plain text: https://xemstudio.com/objects/semi-trailing-arm/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's 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

- A semi-trailing arm pivots on an axis inclined about 50-70 deg, mixing trailing-arm and swing-axle behaviour: the trailing part adds understeer, the transverse part adds roll oversteer, and the two largely cancel (AutoZine).
- Camber changes with wheel travel; it was common on older BMW, Mercedes and Porsche models before multi-link took over (AutoZine).
- Used on: BMW 3-Series (1982), Mercedes 560SEC, Porsche 911, Porsche 928 (Weissach axle).

## Sizes

| parameter | value or range | source |
|---|---|---|
| Pivot axis inclination | about 50-70 deg | AutoZine |

## Where the files are

- AutoZine Technical School: [Suspension: trailing arm, semi-trailing arm, torsion beam, multi-link](https://w.autozine.org/technical_school/suspension/tech_suspension21.htm) — web — Publisher's page; dimensions are facts

## Questions

**What is the Weissach axle?**

A semi-trailing variant that limits braking toe-out (AutoZine).

## 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/)