Rene O.wrote a review of Continental Grand Prix 4000 S II Tire - Clincher on December 11, 2018
Familiarity: I've used it once or twice and have initial impressions
I got the 28 mm version and their real width is at least 30 mm, probably 32 mm if on wide rims. I have a BMC Gran Fondo with disc brakes and these tires juuuust fit. I've been using Gatorskins for years and years and I just may switch permanently to GPs. FYI, the 28 mm version of the GP4000 is definitely wider than the 28 mm Gatorskin. I have yet to take them on dirt/gravel.