If you’ve noticed your bike isn’t shifting as smoothly as it used to, or that the bicycle chain is making a loud clattering sound while you’re pedaling, it’s probably because your one of your bike parts, namely your rear derailleur (the part that changes the rear gears) is out of adjustment.
This can happen for a couple of reasons, but the usual culprit is that the cable that connects it to the shifter has stretched with time and is too loose, making it tough to shift into an easier gear.
The good news is that this is a bike repair problem that’s easy to tackle.
For Road Bikes: Look for the barrel adjuster on the rear derailleur
For Mountain Bikes: Look for the barrel adjuster on the shifter lever
Turn the barrel adjuster counter-clockwise (when looking at the derailleur from the rear) to tighten the cable tension. A pitfall to avoid is thinking of it as “lefty loosey, righty tighty”– in this case loosening the barrel adjuster actually increases tension on the derailleur cable.
*(If your bike is having trouble shifting on to the smaller cogs, the process is the same, but you just turn the barrel adjuster clockwise instead. This also applies if you have a Rapid Rise, or low-normal MTB derailleur)
Continue making quarter turn adjustments until the gears shift smoothly and quietly.
That didn’t work?
- If your bike is very noisy or not shifting properly when it’s in the middle of the cassette, it’s probably because your rear derailleur hanger (where the derailleur bolts on) is bent or needs to be replaced. Take your bike to a shop and have them realign it for you. It should take about 2 minutes.
- If your bike refuses to shift into the highest or lowest cog regardless of cable tension, your high and low limit screws may be improperly set. Try backing the appropriate one out while turning the pedals and see if the derailleur shifts.
- If you recently crashed, look for damage to the derailleur mechanism. If that’s the case, it’s time for a new derailleur.
- Look for rusty or frayed cables, which means it’s time for new cables
- Look for tight bends or kinks in the cable housing leading into the derailleur. If it looks like a very tight loop, you need some slightly longer housing.