Shiraishi Pass

Overview

Shiraishi Pass is an hors-catégorie (HC) climb in Japan, running 7.6 km from a start elevation of 454 m to a summit of 1270 m. Over that distance it delivers a net elevation gain of 816 m at an average gradient of 10.76%, which places it firmly among the hardest sustained ascents a rider can tackle. The HC rating is earned: there is no easy version of a climb that averages double-digit gradients for this long.

The number to watch is the gap between net gain and total ascent. You climb 816 m net, but the total ascent is 954 m — meaning roughly 138 m of the elevation you earn is given back and re-climbed along the way. That undulation matters. It means short descents or false-flats interrupt the climbing, breaking rhythm and forcing repeated re-accelerations. Your legs pay for every metre of that 954 m, not just the 816 m of net gain, so budget your effort against the full total.

How the Gradient Unfolds

The 10.76% average is a blend, not a constant. On an undulating profile like this, the average masks pitches that sit well above it and short recovery zones that sit below. Expect the climb to hit you in waves rather than as one even wall.

• Flatter or descending sections where the road gives back some of the 138 m of undulation — use these to recover, not to hammer.
• Repeated short climbs stacked back to back, each demanding a fresh acceleration after the brief let-ups.
• The steepest ramp, which will be noticeably harder than the 10.76% average — treat it as the crux and hold power in reserve for it.

Pacing Notes

On a smooth climb you can chase even-speed pacing. Here, the undulation makes that a trap: matching speed means spiking power on every ramp and coasting on every dip, which burns matches fast. Instead, pace to even effort — hold a steady sustainable power output and let your speed rise and fall with the gradient. Ease slightly before the steepest ramp rather than surging into it. If you do not know your ceiling, run the FTP estimator before you commit to a number, then ride 5–10% below it on the lower slopes so you have something left for the total 954 m of climbing.

Gearing

At 10.76% average with steeper ramps layered on top, gearing is not optional — it is the difference between spinning and grinding to a halt. Fit a compact or sub-compact chainset and pair it with a wide-range cassette. A 34×32 is a sensible floor; 34×34 gives you real insurance on the steepest pitches and keeps your cadence high enough to protect your legs across the undulation. Check your chainset and cassette combination before the ride — do not discover on the first ramp that you are over-geared.

Summary

• Length: 7.6 km
• Average gradient: 10.76%
• Net elevation gain: 816 m
• Total ascent: 954 m
• Category: HC

Shiraishi Pass rewards discipline over aggression. Respect the full 954 m of ascent, pace to effort through the undulation, and arrive with gearing low enough to keep spinning — and the summit at 1270 m is yours.