Coll de Jau

Overview

Coll de Jau is a Category 2 climb in France, running 10.1 km from a start elevation of 922 m to a summit at 1,505 m. On paper it is a mid-length ascent with a net elevation gain of 583 m, which sits it firmly in the range of a hard hour's tempo work rather than an all-day epic. The category and the length tell you it is serious, but not the whole story.

The whole story is in the gap between the two ascent figures. The net elevation gain is 583 m, but the total ascent is 993 m — a 410 m difference. That means the road does not climb cleanly to the top; it repeatedly gives back altitude and forces you to re-climb it. Every metre of that 410 m is effort spent that the summit elevation never rewards you for, so the climb feels longer and harder than the net gain suggests.

How the Gradient Unfolds

The 5.79% average is a blend, not a description. With 410 m of re-climbing folded in, the gradient swings hard around that mean — flat and downhill stretches drag the average down, while short walls push it far above. The single steepest ramp hits 26.63%, a pitch steep enough to stall you if you arrive in the wrong gear or the wrong mindset.

• Flatter and descending recovery sections that pull the average below 5.79%
• Repeated short climbs where the road gives back altitude, then reclaims it
• A savage maximum ramp of 26.63% — the pitch that dictates your gearing choice

Pacing Notes

On an undulating climb like this, do not chase even speed — the descents and flats will bait you into over-spending, and the walls will bury you. Pace to even effort instead, holding a steady sustainable power output through the climbs and soft-pedalling the give-back sections to recover. Let your speed rise and fall while your effort stays flat.

If you do not know your ceiling, run the FTP estimator first, then ride the sustained pitches just under that number, keeping headroom for the 26.63% ramp where you will spike well above threshold for short bursts.

Gearing

The 26.63% maximum is the gear-deciding number, not the 5.79% average. A pitch that steep demands a compact or sub-compact chainset paired with a wide-range cassette — think 34×32 or 34×34 — so you can keep the cranks turning instead of grinding to a halt. Check your setup before the ride: confirm your smallest chainring and largest sprocket can actually handle a wall this steep, because there is no bailout gear on a 26.63% ramp.

Summary

• Length: 10.1 km
• Average gradient: 5.79%
• Maximum gradient: 26.63%
• Net elevation gain: 583 m
• Total ascent: 993 m
• Category: 2

Coll de Jau rewards riders who respect the numbers behind the average. Pace to effort, gear for the steepest ramp, and treat the 410 m of hidden re-climbing as the real test — not the summit elevation.