From Vielha (3,173 ft / 967 m) to the Port de la Bonaigua (6,798 ft / 2,072 m) it’s 13.9 miles (22.4 km) at an average of 4.9%: 3,625 ft (1,105 m) of climbing on the C-28. Altimetrias.net gives 22.43 km and 3,625 ft (1,105 m), Climbfinder 13.7 miles (22.1 km) and 3,599 ft (1,097 m), and CyclingCols 14.3 miles (23 km) and 3,678 ft (1,121 m), with a maximum of 8%.
What the climb is like
You leave Vielha, the capital of the Val d’Aran, and the first half climbs the valley alongside the Garonne, which rises in these mountains and flows into the Atlantic. The grade is gentle and steady, mostly between 4% and 7%, with no ramps that force you to change rhythm: CyclingCols puts the hardest kilometer at 7%. You pass through Salardú and the Baqueira area, and higher up the landscape opens into treeless high mountain meadows. The road is wide and fully marked, although the pavement was quite cracked in 2022. There’s no shade.
Because it’s so gradual, the challenge is the duration: more than an hour for almost any recreational rider, finishing above 6,500 ft (2,000 m).
History
The Bonaigua is a Vuelta a España classic, and the Tour de France has climbed it too. According to CyclingCols, riders first over the top include Tony Rominger (1993 Tour), Alex Zülle (1995 Vuelta), David Moncoutié (2008 Vuelta), Nicolas Edet (2013 Vuelta) and Thibaut Pinot (2016 Tour).
When to go, water and traffic
June to October. Outside those months snow can close the pass, and even in summer it’s cool at the top and the weather changes fast. Traffic is moderate to light. There are fountains in Vielha and in Salardú (by the roundabout), and in the villages near the road.
What gearing to use
At 3 W/kg (watts per kilo of body weight) and 159 lb (72 kg) you’ll average about 9.9 mph (16 km/h): with a 34x25 that’s about 94 rpm, so on the gentler stretches you can even ride a 36 or 39 up front. Check your combinations in the gear calculator.
Tips
- Bring a jacket and gloves for the descent: at 6,798 ft (2,072 m) it can be cold even in August.
- Eat in Salardú or Baqueira, halfway up.
- For a full day, descend to Esterri d’Àneu and continue to the Port del Cantó from Sort.
Frequently asked questions
How long does it take to climb the Bonaigua from Vielha?
A 159 lb (72 kg) rider on a 21 lb (9.5 kg) bike takes about 1 h 23 min at 3 W/kg (216 W), 1 h 37 min at 2.5 W/kg and 1 h 05 min at 4 W/kg. Work out your own time with your weight and power in the calculator on this page.
Which side of the Bonaigua is harder?
They have similar elevation gain, about 3,600 ft (1,100 m). The Esterri d'Àneu side is a bit steeper (about 12.2 miles / 19.6 km at 5.7-5.8% according to altimetrias.net and Climbfinder) and the Vielha side longer and gentler.
When is the Bonaigua open?
The usual season is June to October. In winter and spring snow can close the pass: check road conditions before you go.