Overview
Lahnerjoch is a genuine hors catégorie climb, and the numbers explain why. Over 13 km it averages 9.16%, dragging you from a start elevation of 793 m to a summit at 1984 m. That is 1191 m of net elevation gain, with 1170 m of total ascent — meaning the road barely lets up long enough to give anything back. There is no easy way to hide from an average this steep held for this long. When a climb sustains better than nine percent for the full distance, every kilometre is a decision, and the HC label is earned rather than awarded.
How the Gradient Unfolds
The defining feature here is relentlessness. A 9.16% average across 13 km is not the product of a gentle run-up followed by one savage wall; it is a road that simply keeps pointing skyward. With only 21 m separating net gain (1191 m) from total ascent (1170 m), there are effectively no descents or flat recovery stretches to break the rhythm — the whole 13 km climbs.
That said, the 23.01% maximum gradient tells you the road is not perfectly uniform. Ramps well into the high teens and low twenties spike above the average, and each one costs you dearly if you hit it already redlined. The smart read is to treat the average as your baseline and the max as your warning: pockets of the climb are far steeper than 9.16%, and they arrive without much runway.
Pacing Notes
On a climb this sustained, pacing is everything. Because there is no recovery terrain, your effort should sit just below threshold from the very first kilometre — going into the red early on a 13 km, 9.16% wall almost always ends in a walk. Anchor your effort to your FTP and resist the temptation to chase the steep ramps out of the saddle; let them come to you and pay the extra cost briefly, then settle back.
If you are not sure what power you can hold for a climb that could take well over an hour, run the numbers first with the FTP estimator so you set off with a target watt figure instead of a feeling. On the 23.01% pitches, accept that you will drift above threshold for a moment — the goal is to minimise time spent there, not to avoid it entirely.
Gearing
Do not under-gear this one. A 13 km climb at 9.16% average with ramps to 23.01% punishes anyone spinning out of range. A 34×32 is the sensible floor for strong climbers, and even then those low-twenties pitches will grind. For most riders a 34×34 is the better call, buying you the extra cadence to keep the pedals turning through the steepest ramps rather than levering the bike forward. If your bike can take it and you value your knees over 1191 m of climbing, err toward the larger sprocket — the easier gear costs you nothing on the shallower sections and saves you on the walls.
Summary
Lahnerjoch is a pure HC test: long, unbroken, and steep from bottom to top. Pace it below threshold, gear it generously, and respect every ramp that spikes past the 9.16% average toward that 23.01% peak.
Length: 13 km
Average gradient: 9.16%
Max gradient: 23.01%
Start: 793 m
Summit: 1984 m
Net gain: 1191 m
Total ascent: 1170 m
Category: HC