# Rear spoiler (vs rear wing)

> What is the difference between a rear spoiler and a rear wing?

- 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/rear-spoiler/ · JSON: https://xemstudio.com/api/geometry?object=rear-spoiler · Plain text: https://xemstudio.com/objects/rear-spoiler/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 spoiler is a lip or dam on the body's trailing edge that 'spoils' unfavourable flow over the body (Sportwing); a wing is a separate airfoil with air passing over both surfaces, creating a pressure difference (CompetitionX).
- Spoilers have lower aerodynamic efficiency than wings (Garry & Le Good, cited in SAE 2018-01-0725), although a NASCAR PIV study found a spoiler made more downforce than a wing because it deflects more flow.
- On a 35% DrivAer racing model, spoiler downforce rose with angle from 20 to 60 deg, with the optimum between 40 and 60 deg; 60 deg cost 8.2% more drag than 40 deg for only 3.5% more downforce.
- Used on: NASCAR stock cars (spoiler vs wing study).

## Sizes

| parameter | value or range | source |
|---|---|---|
| Spoiler lengths tested (35% model) | 40, 80, 120 mm | Cranfield / SAE 2018-01-0725 |
| Spoiler angles tested | 20, 40, 60 deg; optimum between 40 and 60 deg | Cranfield / SAE 2018-01-0725 |
| Downforce ratio at peak ride height | 1.61 (20 deg), 1.89 (40 deg), 1.95 (60 deg) | Cranfield / SAE 2018-01-0725 |
| 60 vs 40 deg | +3.5% downforce, +8.2% drag | Cranfield / SAE 2018-01-0725 |
| 1/12 RC pan car spoiler limit | max 25 mm high, 35 mm long | EFRA |

## Where the files are

- Cranfield University / SAE: [On the Aerodynamics of an Enclosed-Wheel Racing Car (Soares et al., SAE 2018-01-0725)](https://dspace.lib.cranfield.ac.uk/server/api/core/bitstreams/9b476386-44d0-4c0f-a49e-c3372274d351/content) — web — Publisher's page; dimensions are facts
- Sportwing: [Rear Spoiler vs Rear Wing: What's the Difference?](https://sportwing.com/blog/rear-spoiler-vs-rear-wing) — web — Publisher's page; dimensions are facts
- CompetitionX: [RC Wings Explained](https://www.competitionx.com/?p=489) — web — Publisher's page; dimensions are facts
- EFRA: [EFRA Handbook 2010, Appendix 3: Electric Cars](https://www.efra.ws/wp-content/uploads/2010/03/Handb10App3.pdf) — web — Publisher's page; dimensions are facts

## Questions

**Which is more efficient?**

A wing; spoilers have lower aerodynamic efficiency (Garry & Le Good via SAE 2018-01-0725).

**Can a spoiler make more downforce than a wing?**

It can: a NASCAR PIV study found the spoiler deflected more flow and made more downforce, at higher drag.

## 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/)