How To... Index Your Gears

If your bike is clicking, hesitating to change gear, or skipping between cogs, don't panic, it probably just needs the rear indexing adjusted. It's a simple job that only takes a few minutes once you know what you're looking for.

‘Indexing’ refers to each click through your gear shifter and the corresponding movement of rear derailleur (causing the gear to change). In most cases a metal cable links the shifter to the rear derailleur (or ‘mech’) and adjusting the tension on this cable is how we set the indexing.

These tips apply to most standard road and mountain bike gear systems. Some high-end electronic systems will be a little different, so it's always worth checking the manufacturer's instructions if you're unsure.

Step 1: Check the Basics

Before adjusting anything, make sure:

• The bike chain is reasonably clean and lubricated.
• The gear cable isn't rusty or frayed.
• The rear derailleur isn't bent from a recent knock.

There's no point chasing perfect indexing if something else is causing the problem.

Step 2: Set the Limit Screws

The limit screws stop the derailleur from moving too far in either direction. They are normally in a similar position on the back of the rear mech as pictured.

• High (marked 'H') limit screw: Controls how far the derailleur can move towards the smallest cog. Shift into the highest gear and check that the jockey wheel sits directly underneath the smallest sprocket. If it doesn't, make small adjustments until it lines up.
• Low (marked 'L') limit screw: Controls movement towards the largest cog. Shift into the easiest gear and make sure the derailleur lines up underneath the biggest sprocket without trying to push the chain into the spokes.

These screws are safety stops, they're not used for fine-tuning gear changes and once set are often left alone (but are worth checking nonetheless).

Step 3: Adjust the Cable Tension

Now for the indexing.

Shift into the smallest rear cog, then pedal while changing up one gear.

• If the chain doesn’t shift or is slow to climb onto the next sprocket, there's not enough cable tension. Turn the barrel adjuster on the back of the mech anti-clockwise a quarter turn at a time to add tension.
• If the chain wants to jump up two gears or won't settle back onto smaller cogs, there's too much cable tension. Turn the barrel adjuster clockwise a quarter turn at a time to reduce the tension.

After each adjustment, shift through all the gears and see how it feels. Small changes make a big difference, so be patient.

Step 4: Test Every Gear

Run through the full gear range a few times.

The gears should shift smoothly in both directions without hesitation or noisy clicking. If one end of the cassette works perfectly but the other doesn't, double-check both the cable tension and limit screws.

A Few Final Tips

• Make adjustments in quarter-turns rather than large movements.
• Turn the barrel adjuster the direction you want the rear mech to move (ie. to move the mech inward toward the wheel, turn the adjuster anti-clockwise).
• Always pedal while changing gear (ideally with the bike in a work stand).

If you cannot get uniform shifting across the whole range of the cassette, then it is highly likely something else is at fault. The usual culprits are either a bent rear mech hanger (the small metal bracket that connects the rear mech to the frame), or a sticky outer cable restricting the movement of the inner cable. In either case, get your bike to a good bike shop to remedy these issues.

Smooth Shifting

With a little patience, most gear indexing problems can be sorted in under 10 minutes, leaving you with crisp, smooth shifting and a much more enjoyable ride. Now, If you are ever out riding and notice a slight hesitation in gear changes, you can confidently sort it mid-ride with a turn of the barrel adjuster.

If all else fails, drop into Bike Hero’s Chertsey workshop anytime and one of our friendly mechanics would be happy to walk you through these steps to get your gears perfectly indexed.