Col de Portes

Overview

The Col de Portes earns its Category 1 rating through persistence and occasional brutality. At 15.2 km with 811 m of net elevation gain and a total ascent of 1,296 m, the road gives and takes back repeatedly — the gap between net and total ascent tells you the profile is not a clean ramp. Expect undulations, false flats, and at least one section that punishes complacency.

The average gradient sits at 5.33%, which sounds manageable until the maximum of 28.33% enters the conversation. That figure is not a rounding artifact. Somewhere on this climb, the road tips into terrain that will empty most riders unless they are geared and positioned correctly before it arrives.

How the Gradient Unfolds

Starting at 198 m and topping out at 1,009 m, the climb covers significant vertical ground from a low base elevation. The 1,296 m of total ascent versus the 811 m net gain means the road loses meaningful height at some point — riders are not simply grinding upward in a straight line. That recovered descent can feel like relief but acts as a reset: legs that coasted downhill have to re-engage on cold muscles.

The average gradient of 5.33% across 15.2 km produces a workload that accumulates quietly. Riders who go out hard in the opening kilometres — lured by the moderate average — will pay a compounding debt on the steeper ramps higher up. The 28.33% maximum is almost certainly concentrated in a discrete pitch rather than spread across the entire road. Identifying that section early, either from a route preview or from a rider ahead slowing sharply, is the most important tactical move on this climb.

Key gradient characteristics:

• Length: 15.2 km
• Average gradient: 5.33%
• Maximum gradient: 28.33%
• Net elevation gain: 811 m
• Total ascent: 1,296 m (implying descending sections mid-climb)

Pacing Strategy

For a Category 1 climb of this length, effort management relative to your FTP is critical. A 15 km climb at a controlled pace is a sustained threshold or sub-threshold effort for most riders — going over that ceiling early collapses the back half.

Set your ceiling in the first 4–5 km and hold it. The undulating profile means average power will vary naturally; avoid chasing surges on the easier gradients or you will accumulate fatigue before the road demands it. If you do not know your current FTP, the FTP estimator gives a working baseline before you commit to a target power.

When the steep ramp — potentially approaching that 28% maximum — appears, do not try to muscle through it at the same cadence you held on the moderate sections. Shift early, before momentum drops, and accept a lower speed. Standing is a legitimate option on short brutal pitches, but it is metabolically expensive; sit and spin where traction and gearing allow.

Gearing Notes

A 28.33% gradient is steep enough to make compact chainrings and wide-range cassettes non-negotiable for most riders. A 34-tooth inner chainring paired with a 32- or 34-tooth cassette sprocket puts the pitch within reach without grinding. Riders on standard double chainsets who have not pre-checked their low-end gearing will find the maximum ramp a significantly harder problem.

Given the mid-climb descending sections visible in the total versus net ascent numbers, carrying speed into flatter or downhill segments is worth doing — but do not overshoot your recovery. The climb is long enough that conservation always beats aggression here.

For comparison with other Category 1 French climbs and how to structure training around efforts of this duration, see the Alpe d'Huez climb guide.