# Side skirts (ground-effect sealing)

> What do side skirts do on a ground-effect race car?

- Category: Car design › Car aero
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/side-skirts/ · JSON: https://xemstudio.com/api/geometry?object=side-skirts · Plain text: https://xemstudio.com/objects/side-skirts/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

- Side skirts seal the gap between the car's sides and the road so that low pressure built under the floor is not destroyed by air leaking in from the sides (Wikipedia, Ground effect (cars)).
- Lotus sealed inverted-aerofoil sidepods to the ground with flexible skirts on the Lotus 78 (1977) and 79 (1978); the advantage was so large that sliding skirts and then ground-effect floors were banned, with flat bottoms mandatory from 1983.
- Used on: Lotus 78, Lotus 79, Chaparral 2J.
- The file is a reference example built by Xem Studio from the numbers above (Dimensions illustrative; no skirt-gap figure in source.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Lotus 78 season | 1977, five wins | Wikipedia |
| Lotus 79 | 1978, six wins and the drivers' title | Wikipedia |
| Chaparral 2J (fans + skirts) | end of 1970; led to movable-aero ban | Wikipedia |
| Flat-bottom rule | mandatory from 1983 | Wikipedia |
| Ground effect returns to F1 | 2022 | Wikipedia |

## Where the files are

- Wikipedia: [Ground effect (cars)](https://en.wikipedia.org/wiki/Ground_effect_(cars)) — web — Publisher's page; dimensions are facts

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

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

- side-skirts-side-skirt: [STEP](https://xemstudio.com/files/hardware/side-skirts/side-skirts-side-skirt.step) · [STL](https://xemstudio.com/files/hardware/side-skirts/side-skirts-side-skirt.stl) — Side skirt 2000 mm long with a horizontal flange (illustrative section)

## Questions

**Are road-car side skirts the same?**

Styling skirts follow the shape but rarely seal to the ground; the race-car function described here relies on a minimal gap to the road (Wikipedia).

## Fits with

- [Single-element rear wing (race car)](https://xemstudio.com/objects/rear-wing-single-element/)
- [Dual-element (two-element) rear wing](https://xemstudio.com/objects/rear-wing-dual-element/)
- [Swan-neck rear wing mount](https://xemstudio.com/objects/swan-neck-wing-mount/)
- [Gurney flap / wickerbill](https://xemstudio.com/objects/gurney-flap-wickerbill/)
- [Wing endplates / side dams](https://xemstudio.com/objects/wing-endplates/)
- [Front splitter](https://xemstudio.com/objects/front-splitter/)