It is very difficult to make a ranking of the most demanding cycling climbs in the Pyrenees. One of the newest climbs asphalted is Col du Portet, said to be the new Tourmalet by the TdF director, not a joke… This new climb will have real big numbers, and deserves to be among the king climbs in the Pyrenees.
There are a couple of lists you should know.
Highest cycling climbs in the Pyrenees (asfalted):
Port d’Envalira (Andorra/France): 2407 mts height
Port de Cabus (Andorra, just one side) 2300 mts height
Gavarnie-Boucharo (Luz St Sauveur-France) 2270 mts height
Col de Portet (St Lary Soulan-France) 2215 mts height
Cim de Coma Morera (Bourg Madame) 2205 mts height
Cycling climbs with more elevation in the Pyrenees:
Port d’Envalira 1687 mts elevation (from Ax les Thermes)
Col de Pailheres 1601 mts elevation (from Axat)
Gavarnie-Boucharo 1560 mts elevation (from Luz St Sauveur)
Pierre St Martin 1510 mts elevation (from Arette)
Col du Tourmalet 1405 mts elevation (from Luz St Sauveur)
Col de Portet 1400 mts elevation (from St Lary Soulan)
Cycling climbs with the highest average gradient in the Pyrenees:
Erroymendi (from Laugibar) 9,58% for 10,2 km
Burdinkurutxeta (from Bassaburua) 8,76% for 9,3 km
Col de Mente (from St Beat) 8,70% km for 9,7 km
Artzamendi (from Itxassou) 8,61% for 10,3 km
Some of these climbs are included in our trips along the Pyreneess, specially in our Transpyrenees trip. If they are not and you are very interested, just let un know and we will custom the trip for you. We are always happy to include the most demanding climbs in the routes!