This is a very popular pass for cyclists (included on in the Tour de France many times, first in 1907, next in 1948, 1951, 9158, 1961-1963, 1965, 1968, 1970-1971, but then only sporadically thereafter - 1978, 1989 and never again as of 2017 since 1998.
This is also the mountain where Bernard Hinault (The Badger/Le Blaireau) famously crashed in the sixth stage of the 1977 Bastille of Grenoble (see dramatic YouTube footage of the crash and The Badger’s amazing return to his bike after crawling out of the ravine he rode into) which he went on to win, despite this devastating crash.
“The Col de Porte (elevation 1,326 m (4,350 ft)) is a mountain pass situated in the Chartreuse Mountains in the Isère department of France, between Le Sappey-en-Chartreuse to the south and Saint-Pierre-de-Chartreuse to the north. It sits on the D512 between Grenoble and Chambéry, and prior to 1998 was often crossed in conjunction with the Col du Cucheron and the Col du Granier. To the east is Chamechaude, the highest summit in the Chartreuse Massif. There is a small ski resort situated near the col. . . . Details of the climb
From Grenoble, to the south, the climb via the D512 is 17.7 km (11.0 mi) long, gaining 1,116 m (3,661 ft) in altitude, at an average gradient of 6.3%, with the steepest section being at 10%. 2.5 km (1.6 mi) from the summit, it passes the Col de Palaquit (1,154 m (3,786 ft)).”