Lairig Ghru

Lairig Ghru cycling climb profile

Lairig Ghru is a Category 2 climb in Great Britain that asks for patience more than aggression. On paper, 19.9 km at an average gradient of 3.45% can look manageable, but that average hides the real demand: this is a long elevation gain from 212 m to 898 m, with 686 m of net gain and 721 m of total ascent. The numbers point to a climb that trends steadily upward rather than repeatedly resetting, so the cost accumulates even when the gradient is not constantly steep.

The key detail is the spread between the average and the maximum gradient. A 3.45% average suggests a climb that can often be ridden with rhythm, but the 13.6% maximum gradient means there are sharper ramps capable of breaking that rhythm if you arrive overgeared or already riding above threshold. Treat it as an endurance climb with interruptions, not a short punchy effort.

How the gradient unfolds

The total ascent of 721 m compared with 686 m of net elevation gain tells a useful story. There is only 35 m of climbing beyond the net gain, which implies the route is broadly directional: it gains height with limited descending relief. That matters because even shallow gradients become more expensive when there are few meaningful chances to unload the legs.

This is where the average gradient can be misleading. On a climb this long, a rider can feel comfortable early while still slowly drifting above sustainable output. If the steeper sections arrive after that, the 13.6% maximum becomes the point where poor pacing shows up. The climb rewards riders who keep the first half controlled and leave enough torque reserve for the steepest pitches.

Pacing and gearing notes

Ride the lower-gradient sections as controlled pressure, not as free speed. The correct effort should feel like something you can repeat for a long time, closer to steady climbing power than a chase effort. If using power, anchor the main body of the climb below your hard limit relative to FTP, because the steepest ramps will naturally push intensity higher even if speed drops.

Gearing should be chosen for the 13.6% maximum, not the 3.45% average. A setup that feels efficient on the gentler gradients can become costly when the road tilts sharply. The goal is to keep cadence from collapsing on the steepest ramps, because grinding early on a nearly 20 km climb creates fatigue that is hard to recover from before the summit.

Practical takeaway

Lairig Ghru is not defined by a brutal average gradient. It is defined by duration, net elevation gain, and the need to absorb steep ramps without losing the overall pacing plan. Start conservatively, stay seated and efficient where possible, and save the harder work for the gradients that force it. If you are unsure what power range is realistic, estimate it before the ride with the /tools/ftp-estimator and gear the bike for the steepest part, not the average.