Iriyama Pass

Overview

Iriyama Pass is a category 3 climb in Japan, running 11.4 km from a start elevation of 561 m to a summit of 1025 m. On paper it is a modest ascent: 464 m of net elevation gain spread across those 11.4 km. That framing puts it in reach for most fit riders, and the low category reflects a climb that never asks for a single sustained wall of effort.

The number that reshapes the story is total ascent. You gain 464 m net, but you actually climb 765 m over the course of the road. That 301 m gap is descent and re-climb baked into the profile, so the effort you spend is well above what the net figure suggests. Every metre you give back on a dip is a metre you have to earn again, and that changes how you should pace and gear for the day.

How the Gradient Unfolds

The 4.08% average is almost meaningless here. An undulating climb averages out the descents against the ramps, so the mean gradient understates both the flat recovery and the steep pitches. The defining feature is the maximum gradient of 20.65% — a short, brutal ramp that has nothing to do with the gentle average.

• Flatter and recovery sections where the road eases or tips downhill, dragging the average down
• Repeated short climbs that you crest, descend, and then climb again — the source of the 301 m of extra ascent
• A steepest ramp of 20.65% that demands a low gear and a brief, hard surge

Pacing Notes

On a steady climb you would ride even effort. Here, even effort and even speed diverge sharply because of the undulation. Hold your sustainable power output as your ceiling on the steep pitches, but do not chase it on the descents and flats — soft-pedal or recover there rather than burning matches to keep speed constant.

The trap is spiking well over threshold on each short ramp and never recovering across 11.4 km of repeats. Cap the surges on the 20.65% pitch, settle back on the rollers, and let speed vary. If you do not know your ceiling, set it with the FTP estimator before you ride.

Gearing

Gearing is governed by the steepest gradient, not the average. A 20.65% pitch will overgear most riders on a standard setup, so run a compact or sub-compact chainset paired with a wide-range cassette — a 34×32 or 34×34 gives you a bailout for the ramp without wrecking your legs. Check your chainset and cassette before the ride; discovering you are undergeared at 20% is not the moment to find out.

Summary

• Length: 11.4 km
• Average gradient: 4.08%
• Maximum gradient: 20.65%
• Net elevation gain: 464 m
• Total ascent: 765 m
• Category: 3

Iriyama Pass looks gentle at 4.08% average, but the gap between 464 m net gain and 765 m total ascent tells the real story. Pace for the undulation, gear for the 20.65% ramp, and treat the average as the least useful number on the sheet.