Surface (dashed lines, Ω_s) and core (solid lines, Ω_c) rotation rates as a function of surface gravity for 1.1 M_⊙, solar-metallicity models with v_ini = 5 km s⁻¹. Models are computed without (black) and with the Tayler instability, using n = 1 and various values of the calibration constant C_T (green, red, and blue). The thick blue lines show the surface and core rotation of the 1.1 M_⊙, solar-metallicity model from Eggenberger et al. (2022) (E22) computed with GENEC (n = 1, C_T = 216). Large black-filled (open) symbols indicate observed surface (core) rotation rates of sub-giant stars (Deheuvels et al. 2014), while the smaller black dots show core rotation rates of RGB stars (Gehan et al. 2018).