Port de la Bonaigua

Overview

Port de la Bonaigua sits in the Spanish Pyrenees and earns its Category 2 rating through a combination of sustained gradient and a brutal peak ramp that catches underprepared riders by surprise. The climb starts at 1,480 m elevation — already high enough to feel the thinner air — and reaches its summit at 2,078 m, a net gain of 598 m over 9 km. That headline average of 6.65% is deceptive. The total ascent figure of 1,229 m against a net gain of only 598 m tells you everything: the road is not a straight ramp. Gradient changes are significant and frequent, meaning your power output will fluctuate considerably if you're not disciplined.

Gradient Profile

The Lower Slopes

The road begins at 1,480 m, which means your legs are already working against altitude before the gradient even bites. The early kilometres tend to lure riders into a false sense of comfort — the average across the full 9 km is 6.65%, but that figure is pulled up sharply by the upper section. Use the lower slopes to settle into a sustainable rhythm. Resist the urge to push hard just because the gradient feels manageable.

The Crux

The maximum gradient of 20.12% is the defining feature of this climb. A ramp exceeding 20% is not a statistical footnote — it is a gear-selection and pacing event in its own right. At that pitch, even well-trained climbers drop to their smallest chainring-largest sprocket combination and focus purely on cadence and staying seated to maintain rear-wheel traction. The gap between the 6.65% average and the 20.12% peak reflects how concentrated the hardest pitches are. Expect the upper portion of the climb to feel categorically different from the opening kilometres.

The Summit

The summit sits at 2,078 m. At this altitude, aerobic capacity is measurably reduced compared to sea level. Riders not accustomed to Pyrenean elevations should factor this into their perceived exertion targets — your FTP at this height is not the same number you tested at home. Use the FTP estimator to get a realistic sense of your ceiling before you attempt a full-effort ascent.

Pacing Strategy

• Start conservatively. The 6.65% average is achievable for most Category 2-capable riders, but banking effort early to attack the steeper upper ramps rarely works. Begin 10–15% below your target sustainable power.
• Anticipate the steep ramps. With a max gradient of 20.12%, there will be at least one section where the road tilts severely. Do not be caught in too hard a gear. Shift before you need to, not during the worst of it.
• Altitude adjustment. Starting at 1,480 m and finishing at 2,078 m, you are operating in genuinely thin air for the final kilometres. Perceived effort will outpace actual power output. Trust your watts over your lungs if you're riding with a power meter.
• Respect the total ascent figure. The 1,229 m total ascent versus 598 m net gain confirms significant undulation. Energy expenditure is higher than the net numbers alone suggest.

Gearing Recommendations

For a climb with a 20.12% maximum gradient, a compact chainset (50/34) paired with an 11-32 or wider cassette is strongly advisable unless you are an experienced climber with specific strength in steep pitches. A mid-compact (52/36) can work, but leave yourself genuine bailout room on the cassette. On a climb where the gradient swings this dramatically, being over-geared on a single ramp can cost you far more than a few watts of mechanical efficiency on the easier sections.

Compare this climb's demands to similar Category 2 profiles like Alpe d'Huez to calibrate your expectations before arriving at the foot of the Bonaigua.