Coll dels Isards

Overview

Coll dels Isards sits in Andorra and earns its Category 1 rating honestly. At 8.2 km long with an average gradient of 9.57% and a maximum ramp of 29.45%, this is not a climb that rewards optimism or under-gearing. The road gains 787 metres net from base to summit, while total ascent across the full profile reaches 925 metres — meaning there is enough undulation baked in to catch out riders who treat the numbers as a smooth average.

The start elevation of 1,770 m means you are already at altitude when the climb begins. By the summit at 2,557 m, reduced air density is a genuine physiological factor, particularly on the steeper pitches where power demand spikes sharply.

Gradient Profile

The gap between the average (9.57%) and the maximum (29.45%) tells the essential story: this climb is not uniform. Expect extended sections that sit above 10–12% punctuated by at least one section approaching or hitting the near-30% ceiling. A 29.45% gradient is extreme by any measure — comparable to the steepest walls found on the most notorious European climbs.

What to expect, section by section

• Lower slopes: Starting at 1,770 m, the early kilometres establish a rhythm. Use this phase to settle breathing and heart rate before the road tightens.
• Mid-section: The average gradient of 9.57% across 8.2 km means the middle portion is consistently hard. Any relief is short-lived.
• Upper ramps: The 29.45% maximum almost certainly appears in the upper half. This is where under-geared riders are forced out of the saddle, and where those who have gone out too hard will crack.
• Final approach to 2,557 m: Altitude fatigue compounds leg fatigue. Aerobic capacity is measurably reduced above 2,500 m. Keep effort controlled in the kilometres before the summit rather than chasing a number on your head unit.

Pacing Notes

With a 9.57% average over 8.2 km and 787 m of net climbing to deliver, the sustainable power requirement is significant. Riders should target an effort anchored to a realistic percentage of their functional threshold power — typically 75–85% for a climb of this length and severity, adjusted downward to account for altitude. If you need to establish or verify your current FTP before attempting this climb, use the FTP estimator.

The 925 m total ascent figure versus 787 m net gain indicates the road does not simply rise without interruption. Brief descents or flatter passages will tempt riders to surge; resist. Any time gained on a false flat is easily erased on the next steep ramp if it pushes you above threshold.

Gearing Recommendations

The 29.45% maximum gradient is the determining factor for gearing selection. At that angle, even riders with high strength-to-weight ratios will be at or near their lowest usable gear. Recommendations:

• Road: A compact chainset (50/34) paired with an 11-32 or 11-34 cassette is the minimum for most riders. An 11-36 cassette provides meaningful insurance.
• Gravel or endurance bike setup: A wide-range 1x drivetrain with a 40t or 42t rear cog is well-suited if the road surface permits.
• Cadence: Aim to keep cadence above 70 rpm through the steepest pitches. Grinding at 50–55 rpm on a 29% ramp at altitude accelerates neuromuscular fatigue rapidly.

Final Assessment

Coll dels Isards is a serious high-altitude Cat 1 climb with a gradient profile that punishes pacing errors. The combination of consistent double-digit gradients, a near-30% maximum ramp, and a summit above 2,500 m makes it one of the more demanding ascents in the Pyrenean region. Prepare gearing for the worst pitch, pace for the average, and account for altitude from the first pedal stroke.