Col de Gleize

What Kind of Climb Is Col de Gleize?

Col de Gleize is a Category 1 climb in France that earns its rating honestly. At 9.6 km long with an average gradient of 8.6% and a maximum that spikes to 18.66%, this is not a road that forgives early aggression. The 936 m of total ascent packed into under 10 km puts it firmly in the territory of climbs that test both threshold power and muscular endurance simultaneously.

The start elevation of 860 m means you are already at altitude before the real work begins, and the summit at 1,688 m means the air is noticeably thinner by the top — a factor worth accounting for if you are coming from sea level.

How the Gradient Unfolds

With an 8.6% average across 9.6 km, there is no flat section to speak of. On a climb like this, an average that high almost always signals sustained double-digit pitches interrupted by only brief, marginal recoveries rather than genuine flat ramps.

The 18.66% maximum is the number that demands the most respect. A gradient of that severity, wherever it sits on the road, will force a significant gear selection decision. Hit it in too large a gear after 6 or 7 km of sustained effort and your legs will tell you immediately.

Gradient Breakdown at a Glance

• Length: 9.6 km
• Average gradient: 8.6%
• Maximum gradient: 18.66%
• Total ascent: 936 m
• Category: 1

Pacing Strategy

The 8.6% average is the number to anchor your effort around, not the maximum. Riders who key off the steeper ramps and surge tend to accumulate fatigue that surfaces badly in the final kilometers.

A sensible approach:

• Set your ceiling early. If you know your FTP, target somewhere in the 80–90% range for the first half. A climb averaging 8.6% over 9.6 km is long enough that going out at threshold will cost you on the back half.
• Anticipate the steep ramps. When the road tilts toward the 18% maximum, shift before you need to. Trying to spin through a near-19% pitch in a gear that is one or two steps too large will spike your heart rate and burn matches you need later.
• Do not chase recoveries. Any brief easing in gradient on a climb averaging 8.6% is relative — it may still be 6–7%. Use those sections to reset breathing rather than accelerate.

Gearing Notes

For most riders, a compact chainset (50/34) paired with an 11-32 or wider cassette is the practical choice. The 18.66% maximum pitch is demanding enough that riders carrying any fatigue from earlier in a ride will want a genuine bail-out gear available.

If you are running a standard 53/39, assess your fitness and freshness honestly before committing. At 936 m of climbing spread across 9.6 km, grinding out the top third of a Category 1 climb in too large a gear is a common way to damage an otherwise well-executed effort.

Use the FTP estimator to get a realistic picture of what watts-per-kilo you can sustain across a climb of this length before you set your targets.

Bottom Line

Col de Gleize is a proper Category 1 test: long enough that pacing matters from kilometer one, steep enough at its maximum that gearing is a genuine tactical decision, and consistent enough in average gradient that there is nowhere to hide. Ride it with respect for the numbers and it is a deeply satisfying climb. Ignore them and the final few kilometers will make the point for you.