Col du Joly

What to Expect on the Col du Joly

The Col du Joly earns its Hors Catégorie rating honestly. Over just 7.4 km it climbs 940 metres — from a start elevation of 1,152 m to a summit at 1,992 m — at an average gradient of 11.28%. That average is not a smooth curve; it reflects a relentlessly steep road where short moments of relief exist only to reset you before the next hard pitch.

With a maximum gradient of 22.8%, there are sections that briefly approach the limits of what most standard road gearing can handle at any reasonable cadence. This is not a climb where you can settle into a rhythm and cruise. Every kilometre demands active management of effort.

Gradient Breakdown

The headline numbers — 11.28% average, 22.8% maximum — tell the essential story:

• Average gradient of 11.28% places the Col du Joly among the steepest sustained climbs in the Alps. For context, sustaining this gradient for 7.4 km requires a well-calibrated power-to-weight ratio and the discipline to resist going anaerobic early.
• Maximum gradient of 22.8% means at least one ramp will push into territory where even riders with compact chainsets and wide-range cassettes will be searching for a gear. At gradients above 20%, technique matters: stay seated where possible to keep rear-wheel traction, keep upper body relaxed, and avoid surging.
• 940 m of total ascent in 7.4 km produces a climb with almost no flat or descending sections to reset your legs. Every metre of road goes up.

Pacing Strategy

The Col du Joly punishes riders who open too hard. With an average gradient above 11%, a pace that feels merely uncomfortable in the first two kilometres will accumulate fatigue fast enough to blow up your effort before the summit.

Recommended approach:

• Set a power ceiling at the base. Use your FTP as the anchor. On a climb this steep and this short (under 30 minutes for competitive riders, longer for most), aim to hold a sustainable percentage of FTP from the first pedal stroke rather than building into it. The gradient won't let you ease in for long before it forces your hand.
• Anticipate the 22.8% ramp. If you have course data or have pre-loaded the profile, identify where the steepest section falls. Arrive at it with something in reserve. If you don't know where it sits, treat any sudden steepening as a cue to drop a gear immediately rather than grinding through.
• Cadence management. On sustained double-digit gradients, a lower cadence (60–70 rpm) is metabolically cheaper for many riders than spinning a smaller gear rapidly. Experiment in training, but on a climb with sections approaching 23%, you will likely be in your lowest gear regardless — the question becomes whether you can keep it turning smoothly.

Gearing Notes

Do not underestimate how much a 22.8% ramp costs at the end of an already hard 7 km. If you are riding a compact chainset (50/34), a cassette with at least a 32-tooth sprocket is sensible. Riders on standard chainsets should honestly evaluate whether they can turn the gear over on the steepest sections without damage to knees or rhythm. Use the FTP estimator to stress-test your power target before the ride.

For those pre-riding the climb or targeting a time, the 940 m ascent figure is a reliable number to use in energy expenditure models — the elevation gain is large enough that even well-trained riders will need to account for it in fuelling, particularly if the Col du Joly features as part of a longer day in the mountains.