Bike Gears, Cassettes & Shifters — A Plain-English Guide for UK Cyclists

Gearing is one of the most technical areas of cycling, but understanding the basics helps you make smarter buying decisions — whether you're replacing a worn cassette or upgrading your whole drivetrain.

How Bicycle Gearing Works

Your gears are made up of the chainset (front chainrings), the cassette (rear sprockets), the chain, and the derailleurs that move the chain between them. The shifters on your handlebars control the derailleurs via cables or electronic signals.

Cassettes — Speed and Range

Cassettes are described by the number of sprockets (e.g. 11-speed) and the range of teeth (e.g. 11-32T). More sprockets = closer gear steps = smoother shifting. A wider range (e.g. 11-42T) gives you lower gears for climbing. Match your cassette speed to your shifters and rear derailleur.

Shifter Types

• STI levers (Shimano) / Ergopower (Campagnolo) — integrated brake/shift levers for drop bar bikes
• Trigger shifters — thumb-operated, common on mountain bikes
• Grip shifters — twist to change gear, popular on hybrids and kids' bikes
• Electronic shifters (Di2, eTap, AXS) — precise, low-maintenance, but premium priced

Compatibility Is Everything

Mixing components from different brands or speed groupsets is a common source of problems. As a rule, keep your shifters, cassette, chain, and derailleurs within the same speed groupset (e.g. all Shimano 10-speed). Some cross-compatibility exists but always check before buying.

When to Replace

Replace your chain regularly (every 1,500–3,000 miles) to extend cassette life. A worn chain accelerates cassette wear significantly. Use a chain wear indicator tool — they cost just a few pounds and save you money in the long run.

Browse our gears, cassettes and shifters to find compatible components for your drivetrain.