A Specialized Tarmac SL6 (2018 to 2020) uses a IS42 integrated upper headset (integrated, 42 mm). The dimensions, how to confirm it on your frame, and how it compares to the neighbouring standards.
Updated 05 September 2026.
What headset does a Specialized Tarmac SL6 (2018 to 2020) use?
The headset fitment standard on a Specialized Tarmac SL6 (2018 to 2020), and how to pick the right part.
| Frame | Specialized Tarmac SL6 (2018 to 2020) |
|---|---|
| Headset standard | IS42 (integrated, 42 mm) |
| Cup / bearing outside diameter | 41.8 to 42.0 mm bearing outside diameter |
| Steerer diameter | 28.6 mm (1 1/8 in) |
The Specialized Tarmac SL6 (2018 to 2020) uses a IS42 integrated upper headset (integrated, 42 mm), a 27.2 mm class seatpost, a 12x100 mm front thru-axle at the front (12 mm x 100 mm, front) and a braze-on front derailleur.
The 27.2 mm figure is the mainstream disc-road interface; many of these frames ship a proprietary aero-shaped post, so confirm the exact part. The bottom bracket is covered on its own page.
SOURCES: Park Tool, Standardized Headset Identification System (SHIS) · BikeGremlin, Bicycle headset bearing standards (SHIS) · BikeRadar, Road bike axle standards: the complete guide
Questions and answers
What headset does a Specialized Tarmac SL6 (2018 to 2020) use?
A Specialized Tarmac SL6 (2018 to 2020) uses a IS42 integrated upper headset (integrated, 42 mm).