Bonari Pass

Overview

Bonari Pass is a Category 2 road climb in Japan, running 15.1 km from a start elevation of 288 m to a summit at 977 m. Over that distance it delivers a net elevation gain of 689 m, giving it the sustained, long-haul character you would expect from a mid-category ascent rather than a short wall.

The number to watch is the gap between net gain and total ascent. You climb 689 m net, but the road actually forces 849 m of ascent — 160 m more than the elevation difference between bottom and top. That surplus is undulation: sections where the road dips and you have to re-climb what you just gave away. On paper the climb gains 689 m; in the legs it feels like 849 m, and your pacing has to account for the harder number.

How the Gradient Unfolds

The 4.58% average is an accounting figure, not a riding experience. Because 160 m of the total ascent is spent recovering from descents, the true climbing pitches are steeper than the average implies — the road banks its difficulty into shorter, sharper ramps rather than spreading it evenly. The steepest recorded pitch hits 15.33%, roughly three times the average.

• Flatter and recovery sections where the road dips, dropping you below the average gradient
• Repeated short climbs that re-gain the lost elevation, keeping the effort punchy
• A steepest ramp at 15.33% that demands a low gear and a deliberate change of rhythm

Pacing Notes

On a smooth, evenly graded climb you can hold constant speed. Bonari Pass is not that climb. With 160 m of undulation, chasing an even speed means overcooking the steep ramps and freewheeling the dips — a fast route to blowing up. Pace to even effort instead: hold a steady, sustainable power output through the ramps, let your speed rise on the shallow and descending sections, and accept that your pace will swing while your effort stays flat. If you do not know your ceiling, run the numbers through the FTP estimator before you commit to a target, then ride a few watts under it on the early pitches.

Gearing

The 15.33% maximum sets your gearing requirement, not the 4.58% average. On a 15.1 km climb where you will be tired by the time the steep ramps arrive, gear for the worst pitch. Run a compact or sub-compact chainset paired with a wide-range cassette — a 34×32 or 34×34 low gear keeps your cadence up when the road kicks to 15% and stops you grinding to a crawl. Check your setup before the ride: confirm the cassette and derailleur can actually take the sprocket you are counting on.

Summary

• Length: 15.1 km
• Average gradient: 4.58%
• Maximum gradient: 15.33%
• Net elevation gain: 689 m
• Total ascent: 849 m
• Category: 2

Bonari Pass rewards riders who read past the average. Pace to even effort, gear for the 15.33% ramp, and treat the 849 m of total ascent — not the 689 m net — as the real measure of the day.