Col d'Allos

Overview

The Col d'Allos is a Category 1 Alpine climb that demands respect from the first pedal stroke. Starting at 1,537 m and topping out at 2,239 m, the road covers 9.3 km with a net elevation gain of 702 m and a total ascent of 1,170 m — the difference indicating that the road is not a straight ramp but has enough undulation to accumulate additional climbing within the overall gain. At an average gradient of 7.56%, this is a sustained, honest effort from bottom to top.

Gradient Profile

The average of 7.56% is telling in itself, but the maximum gradient of 21.48% reveals where the climb becomes genuinely brutal. A figure like that — more than double the average — means there are short, sharp sections that bear no resemblance to the sustained tempo the rest of the climb might lull you into.

Expect the ascent to play out roughly like this:

• Lower slopes: The climb begins at 1,537 m, already at altitude, so the air is noticeably thinner than a valley-floor start. Early ramps in the 6–8% range are likely to set the tone.
• Mid-section: This is where many riders burn matches trying to hold a pace that felt comfortable on the lower slopes. The gradient varies but the sustained nature of a 9.3 km effort at Category 1 difficulty means there is no genuine recovery.
• Upper ramps: The 21.48% maximum gradient is likely concentrated here or in a sharp mid-climb kicker. When it arrives, it will feel abrupt. Riders who have not managed effort through the lower two-thirds will crack.

Pacing Strategy

With 9.3 km and 7.56% average, this climb will take most trained amateur riders somewhere between 45 minutes and over an hour, depending on fitness. That duration demands pacing discipline.

Key principles:

• Set your power or perceived exertion target based on your FTP. For a climb this length, working at roughly 90–95% of FTP is a realistic ceiling — not a floor.
• Do not spike effort on the lower slopes. The altitude gain from 1,537 m is continuous, and your aerobic capacity will be taxed increasingly as you rise.
• When the 21%+ ramp appears, accept a brief power spike rather than try to smooth it with speed — you will need to push harder momentarily, but resist the urge to empty the tank chasing an even split through it.
• Use the FTP estimator to calculate a realistic watt target before attempting this climb.

Gearing Advice

A maximum gradient of 21.48% is no place to be out of gears. On a climb where the average already sits above 7.5%, arriving at a 21% ramp with nothing left in the cassette is a serious problem.

• A compact chainset (50/34 or 46/30) paired with an 11-32 or 11-34 cassette is strongly advisable.
• Riders on a standard double should be confident they can sustain 21%+ in their lowest available gear — if there is any doubt, swap the cassette before the day.
• The total ascent figure of 1,170 m (versus the net gain of 702 m) confirms that legs will carry cumulative fatigue even before the hardest gradients arrive.

Summary

The Col d'Allos cycling climb is not a climb to underestimate based on its 9.3 km length. The Category 1 classification is earned: sustained gradients averaging 7.56%, a vicious 21.48% maximum, and a starting elevation that removes any low-altitude comfort from the equation. Pace conservatively, gear appropriately, and treat every percentage point of that average gradient as a reminder that the climb is working on your legs even when it feels manageable.