Gearing for climbing: the arithmetic nobody does

There is a persistent belief in road cycling that low gears are an admission of weakness. It has cost a great many riders a great many good days, and it survives entirely on vanity — because the arithmetic is not ambiguous.

Gearing does not decide how much power you produce. It decides the cadence at which you produce it, and cadence decides whether a climb is sustainable or a grinding, knee-loading slog.

The arithmetic nobody does

Your speed on a climb is set by your power and your weight. Your cadence is set by your speed and your gear. So if a climb has you moving at 8 km/h, the only question is what that forces your legs to do.

Read the top row again. On a 34×28 — the setup on an enormous number of road bikes — riding at 6 km/h means turning the pedals at about 35 rpm. That is not climbing; that is a leg press with a view. Every rider who has been reduced to zig-zagging up a steep road has met this table without knowing it.

Why low cadence on a climb is expensive

• Force per pedal stroke goes up. The same power at half the cadence means roughly twice the force on each stroke — loading the knee, and recruiting fast-twitch fibres that fatigue far sooner.
• You lose the ability to modulate. At 90 rpm you can respond to a steepening ramp by pushing slightly harder. At 45 rpm you have no headroom: the next ramp stops you.
• Balance gets harder. Below about 50 rpm on a steep road, staying upright starts to take real effort, which is why very steep climbs feel technically difficult as well as hard.
• It hurts your knees. High-force low-cadence work is one of the recognised contributors to cycling knee pain — see knee pain from cycling.

What to change, in order of cost

1. A bigger cassette. Going from a 28 to a 32 at the back is a cheap part, sometimes fits your existing derailleur, and buys a meaningful improvement. Start here.
2. A derailleur with more capacity, plus a big cassette. If your current one cannot take 32 or 34, the pair is still far cheaper than a groupset.
3. A smaller inner ring. Sub-compact chainsets exist precisely because the market finally accepted this problem. Effective, more involved to fit.
4. A different bike. Only if you are replacing anyway — in which case, choose the one with the gearing your local roads actually demand.

Pick gearing for the worst climb, not the average one

Riders choose gearing for the riding they mostly do, then meet one 18% ramp and walk. Gearing costs almost nothing when you do not need it — an extra sprocket you never use has no meaningful weight or efficiency penalty — and costs you the day when you need it and do not have it.

Before a trip or a target event, look at the steepest sustained section on the route and check the table above at the speed you expect to be doing there. How to read a route profile covers how to find that number, and it is worth doing properly — profiles routinely hide the steepest kilometre.

The indoor complication

On a direct-drive trainer your cassette is the trainer's, not the bike's, so your indoor gearing may be nothing like your outdoor gearing. That matters more than riders expect when a session asks for a specific cadence, and it is worth knowing which gear gives you 85 rpm at your threshold power before a workout starts rather than hunting mid-interval.

Moveee Indoor follows the real gradient of whatever route you are riding, so a 14% ramp on a road you are previewing arrives as 14% of resistance — which is an unusually honest way to find out whether your gearing is adequate for an event before you fly somewhere to discover it is not.

The only thing worth caring about

Nobody at the top of a climb knows what you were riding, and nobody who matters would care. What they would notice is that you got there riding rather than pushing, and were still able to enjoy the descent. That is what gearing buys, and it is available for the price of a cassette.