Saramsha

No. 038  ·  24 October 2026

The Gear You Never Use

A derailleur gear is only ever two tooth-counts — a chainring up front, a sprocket out back — divided into a ratio. Shift through all twenty-two combinations and the chain line itself will show you something your legs already know: most of them run it almost straight, and two of them run it badly diagonal.

All 22 gears, coloured by chain angle. Tap any cell to jump to it — the two worst sit in opposite corners.

About this piece

Two numbers and a chain between them

A derailleur drivetrain is simpler than it looks from the saddle. There is a small set of chainrings bolted to the crank — this page gives you the common road-bike "compact" pair, 50 teeth and 34 teeth — and a cassette of sprockets bolted to the rear wheel, here an 11-speed 11–32 spread. Pick one of each and you have picked a gear ratio: front teeth divided by rear teeth. Multiply that ratio by how far the wheel travels in one full turn — its circumference, taken here as a standard 700c wheel at about 2.1 metres — and you get the development: the distance one full pedal stroke pushes the bike forward. Multiply that by cadence, the rate you're actually turning the pedals, and you get road speed. Every number in the panel on this page falls out of those three steps; there is no other mechanism hiding underneath.

What the numbers don't show is where the chain physically sits while it does this, and that's the part most cyclists only learn by ear — a odd rattling in certain gears — rather than being told. A chainring is not perfectly centred on the bottom bracket axle: the big ring sits further out from the frame than the small one, by roughly the width of a finger. A cassette sprocket is not centred on the rear axle either: the smallest sprocket sits at the outer edge of the freehub, the largest sits closest to the wheel, and the eleven in between step evenly across the gap. The chain itself is rigid sideways only up to a point — it can flex a little to cope with a short diagonal run, which is exactly what happens whenever the front and rear positions don't line up.

Why the corners are the ones to avoid

Put the two sets of positions next to each other and a pattern falls out: the big ring's natural partner is a small sprocket, because both sit toward the outside of the drivetrain, and the small ring's natural partner is a large sprocket, because both sit toward the inside, closer to the frame. Pair them the other way — big ring with the largest sprockets, or small ring with the smallest — and you've put the front and rear as far out of line as the drivetrain allows. The chain has to run diagonally across that gap on every single link, which is the one thing a bicycle chain is worst at: it rubs the front derailleur cage, it wastes a measurable slice of your pedalling effort bending sideways instead of pulling straight, and it wears the sideplates and the sprocket teeth faster than a straight run ever would. None of this stops the bike — it still goes — which is exactly why so many riders use the two forbidden corners for years without ever being told to stop.

The grid beneath the diagram is every one of the 22 combinations at once, coloured by exactly the angle described above, computed from each part's real axial offset and a typical chainstay length. The pattern it draws — green down one diagonal, red bleeding into the two opposite corners — is the same pattern a mechanic means when they say "don't cross-chain": not a vague caution, but two specific corners of a 2×11 grid that happen to share a ratio you can usually get, with far less wear, from an adjacent and nearly identical gear one sprocket over.

Figures used: a 50/34 compact crankset, an 11-speed 11-32 cassette (11, 12, 13, 14, 16, 18, 20, 22, 25, 28, 32 teeth), a 700×25c wheel (≈2.105 m circumference) and a 405 mm chainstay — all typical values for a modern road bike, not measurements of one specific model. Axial offsets (chainring spacing ≈43.5 mm, cassette spread ≈40 mm) are likewise representative rather than exact to any single groupset, chosen to match the angles riders actually report feeling.