Four repairs that cover most of what goes wrong

Symptom: The pad touches the rim on one side only, or the wheel drags after a bump.

1. Spin the wheel and confirm the rim itself is straight — if it wobbles side to side, the wheel needs truing first and no brake adjustment will fix it.
2. Squeeze the calliper closed by hand so both pads touch the rim evenly, then hold that position.
3. Loosen the centring screw a quarter turn, let the calliper settle, and retighten.
4. Release and spin. If one pad still drags, adjust the small grub screw on that arm a quarter turn at a time.
5. Finish by squeezing the lever hard ten times, then re-check — cables bed in and change the setting.

Symptom: The chain sits between two cogs, clattering, and refuses to settle.

1. Shift to the smallest sprocket and check the chain sits cleanly with no tension in the cable.
2. Shift up one. If it hesitates going up, add tension: turn the barrel adjuster anticlockwise one click.
3. If it hesitates coming back down, remove tension: clockwise one click.
4. Work one click at a time, testing after each. Two clicks in the wrong direction is the usual reason people give up.
5. If nothing helps across the whole cassette, look at the derailleur hanger from behind — a bent hanger cannot be adjusted out.

Symptom: Chain wear gauge drops in at 0.75, or the chain skips under load on a new cassette.

1. Measure first. Replacing an unworn chain achieves nothing and costs money.
2. Note the routing through the rear derailleur before breaking the old chain — photograph it if unsure.
3. Size the new chain against the old one link for link, not against the bike.
4. Join with the correct quick link for the speed count. Nine-speed links are not ten-speed links.
5. Seat the link by standing on the pedal with the brake held. It should click audibly.

Symptom: The same tyre is soft every few days, with no obvious hole.

1. Inflate the removed tube and listen, then pass it near your lips — skin finds leaks that ears miss.
2. Mark the hole, then line the tube up against the tyre to find the matching spot.
3. Run a cloth or gloved finger around the inside of the tyre. Repeat punctures are almost always a thorn or wire still embedded.
4. Check the rim tape covers every spoke hole. A slipped tape causes punctures on the inner face of the tube.
5. If the hole is on the inner face and the tape is fine, the tube was pinched during the last fitting.