I run a mix of the sizes listed above, namely:
F. 265/40R21
R. 295/35R21
No rubbing. Sidewall height F—>R almost identical.
Keep in mind that the 21” Uberturbines are 1” (25.4mm) wider in the rear than they are in the front (10.5” vs 9.5”) so 30mm wider tires makes a lot of sense and result in an almost identical relationship between wheel and tire on both axles. The upsized dimensions (from OEM) serve to eliminate the s_t_r_e_t_c_h_e_d appearance of the OEM spec while also adding a measure of ride improvement and damage resistance while also filling out the wheel wells for a more athletic stance (ok, that last one is a bit subjective, but I like it).
While technically feasible, I would not recommend running 275/35R21 all around given the significant wheel width difference: there will be a significant difference in appearance from front to rear.
Others have opted to run a 285/40R21 spec on the rear which is also a great choice (overall a bit taller but slightly less wide).
Good luck with your choice and, even more so, with finding your chosen spec in stock. Stay well.
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