How to fix a skipping chain

Honestly, there aren't many things more annoying than a skipping chain when you're trying to pedal. It's not just irritating though—it can actually wreck your bike frame or drivetrain if you ignore it. I'll walk you through what's going wrong and how to sort it, step by step. Whether you ride a road bike, a mountain bike, or just a hybrid for commuting, the basic ideas are all the same.

Why is my bike chain skipping when I pedal hard?

This is the classic problem, right? You stomp on the pedals and feel that awful slip. It's almost always because your drivetrain is worn out. Chains stretch over time—they call it "chain wear" or "chain stretch"—and once it's stretched, it doesn't sit right on the gear teeth anymore. So under power, it rides up and then lets go. That's the skip.

Could be a stiff link, a bent derailleur hanger, or a chipped tooth too. But nine times out of ten, it's a worn chain with a worn cassette that's the real culprit.

How to diagnose a skipping chain (Checklist)

Don't just start buying parts. Work through this list first—it'll save you time and money. Go in order.

• Check for a stiff link: Spin the cranks backward and watch the chain go through the derailleur pulleys. Any link that doesn't bend smoothly? That's a stiff link, and it'll cause a skip every time it hits the cassette.
• Inspect chain wear: Grab a chain checker tool. If it drops into the 0.75% or 1.0% mark, your chain's done. Replace it now.
• Examine cassette teeth: Look at the teeth on your rear gears. If they're pointed and hooked, like shark fins, that's wear. If you've been riding a worn chain too long, the cassette's toast too.
• Check chainring teeth: Same deal with the front chainring(s). Hooked or pointed teeth are a sign. Missing teeth? That's obvious damage.
• Test derailleur alignment: Look from behind the bike. The derailleur hanger should be perfectly vertical. A bent one messes up shifting and causes skipping.
• Assess cable tension: If the skip happens when you shift, the cable tension might be off. A poorly indexed system can leave the chain sitting between gears.

Step-by-step repair guide

Once you know what's wrong, here's how to fix it. Most of the time, you're looking at replacing the chain and cassette together.

1. Replace a worn chain

If your chain is worn but the cassette and chainrings still look okay, a new chain might do the trick. Use a chain breaker to remove the old one. Count the links so you get the right length. Thread the new chain through the derailleur and connect it with a quick link or pin. Give the cranks a spin to make sure it runs smooth.

2. Replace the cassette

If those cassette teeth are hooked, you've got to swap it out. Take the rear wheel off. Use a cassette lockring tool and a chain whip to unscrew the lockring. Slide the old cassette off, slide the new one on. Tighten the lockring to the manufacturer's torque specs—usually around 40 Nm. Then put the new chain on, like I said above.

3. Fix a stiff link

Find the stiff link. Grip it on both sides and flex it sideways. If that doesn't work, put a drop of lube on it and work it in. For really stubborn ones, you can use a chain tool to slightly loosen the rivet—but be careful not to push it all the way out.

4. Straighten a bent derailleur hanger

You'll need a derailleur hanger alignment tool for this. If you don't have one, any decent bike shop can do it in a few minutes. Don't try bending it by hand—you'll probably snap it. A bent hanger makes shifting awful and can cause the chain to drop.

Expert insights: When to replace the whole drivetrain

Most experts say to replace your chain every 1,500 to 2,000 miles. If you let it wear past 1.0%, you're almost certainly looking at a new cassette and chainrings too. That's way more expensive. Check out the cost table below.

Here's a pro tip for you: if your bike's got more than 3,000 miles and you've never changed the chain, just plan on replacing the cassette at the same time. You'll save yourself from doing the job twice.

Frequently asked questions

Prevention tips

• Clean and lubricate: A clean chain lasts way longer. Use a degreaser every 200 miles and put on some good wet or dry lube.
• Monitor chain wear: Use a chain checker every month. Replace the chain at 0.5% wear to save your cassette from getting wrecked.
• Shift smoothly: Avoid cross-chaining—that's big chainring with big cog—and shift when you're not putting full power down.
• Inspect after wet rides: Water and grit wear things out fast. Dry and re-lube your chain after riding in the rain.