Rear spoiler (vs rear wing) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/rear-spoiler/  (sheet CC BY 4.0)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- 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).

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

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Cranfield University / SAE: On the Aerodynamics of an Enclosed-Wheel Racing Car (Soares et al., SAE 2018-01-0725) — web — Publisher's page; dimensions are facts — https://dspace.lib.cranfield.ac.uk/server/api/core/bitstreams/9b476386-44d0-4c0f-a49e-c3372274d351/content
- Sportwing: Rear Spoiler vs Rear Wing: What's the Difference? — web — Publisher's page; dimensions are facts — https://sportwing.com/blog/rear-spoiler-vs-rear-wing
- CompetitionX: RC Wings Explained — web — Publisher's page; dimensions are facts — https://www.competitionx.com/?p=489
- EFRA: EFRA Handbook 2010, Appendix 3: Electric Cars — web — Publisher's page; dimensions are facts — https://www.efra.ws/wp-content/uploads/2010/03/Handb10App3.pdf

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=rear-spoiler