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How to Tighten a Bike Chain?

tightened bike chain

Cycling is an epic sport, and its popularity is growing more and more every year. Bikes are an excellent way of getting around and a great way to stay in shape. Bikes, like any mechanical vehicle, require attention every so often to keep them in top form. We often get asked advice on bike maintenance, and one of the most common questions is how to tighten a bike chain.

Tightening a bike chain can be a little more challenging than people might think because there are many reasons it can be slack. In this article, we’re going to speak about why a slack chain isn’t good for your bike, why the chain might be slack, and also, we will speak about how it can be fixed.

Why You Don’t Want a Slack Bike Chain?

a slack bike chain
Photo by Chris Becker on Unsplash

Having a slack chain at the time might feel like it doesn’t make much difference, but it does, and if left broken can cause so many issues and massively affect your performance.

Affects performance

The first thing to mention is how much a slack chain can affect performance. Firstly not only does it make shifting around the cassette really slow and might not go into gear correctly. You might also find a slack chain can cause the chain to slip and fall off the chainrings easily.

Can be dangerous

A slack chain doesn’t just underperform but can also be very dangerous. When the chain is slack, it is prone to slipping or falling off. This means the pedal can give way, and when that happens, it’s very easy to lose your balance and fall off. You also have the issue that a slack chain can break very easily, leaving you stranded on a ride.

Can damage your bike

When a chain is slack, it will not be able to work as it should. This can cause a lot of problems, such as it can cause your derailleurs to break by the chain skipping out and getting caught. It can hit your frame, scratch it, and even cause you to fall off and drop your bike.

Causes excessive chain wear

When a chain is slack, it doesn’t work as it should. Chains are designed to be under constant tension, and if not, they are constantly engaging and disengaging while you ride. This can cause your chain to wear down quickly and, in the worst case scenario, break.

Why is My Bike Chain Slack?

slack bike chain
Photo by Brina Blum on Unsplash

There are many reasons why you might find the chain to be slack and start causing you issues. Here are the most common;

Not enough tension

Chains are designed to be under tension, and a derailleur will have a tension screw that you can adjust to tighten the chain. This is very easy to do, and it’s common for people to have this too loose.

Related: How to Clean and Lube Your Bike Chain – 9 Easy Steps

The chain is too long

When a chain is too long, no matter how much tension is in the drivetrain, it won’t be enough. If you have just had your bike serviced or serviced your bike yourself, you might have left the chain too long, and this could be causing your bike’s chain to have slack.

The chain is heavily worn

If you don’t often change your chain, then you will find it starts to stretch. A chain can get much longer if not looked after, and this can actually cause the bike’s chain to have less tension and feel loose.

How to Tighten Your Chain

tightened chain

There are many reasons why your chain might be loose, and many solutions to fix it to create the tension you need. Here’s our step-by-step guide to getting the chain tight again.

Step One: Check Chain Length

The first thing you will need to do is check the chain is the correct length. You will need to put the bike in the smallest ring at the front and the smallest at the rear. If the chain is loose, you will need to remove some links to ensure the chain’s tightness. Learning basic bike maintenance will go a long way to saving you money on repairs and also helping you fix unexpected on the road issues, there are alternative methods to remove a bike chain without tools if needed.

Step Two: Check Chain Health

The next thing you will need to do is check the chain’s health. We recommend using a chain checker to see how much it has stretched over its life. If it’s over 1.5mm on the check, you will need to get the chain changed over.

Step Three: Check the tension screw

Now it’s time to check your tension screw. On the rear of the derailleur, there will be a single screw on its own this is called the derailleur tension screw. If the chain is slack, then you are going to want to tighten this up.

You can do this by adjusting it. Typically you will need a small Allen key, such as a 3mm. To tighten, you will need to turn it clockwise, and to slacken the chain, you will need to go anti-clockwise.

You will want to tighten it until the chain is under tension. You will have to be cautious not to tighten it too much, or your gears might struggle to change smoothly. Ensure taking your bike out for a spin after checking it all works ok.

What if It’s Still Slack?

still slackened chain

If the chain is still slack, then it will need further investigation. This could be a multiple of different issues, such as a broken derailleur, or you might have a bent rear mech. We recommend investigating further, and if you can’t find the issue go to your local bike shop and speak to a qualified mechanic.


Having a slack bike chain can be very annoying and not just cause the chain to slip off or wear extra, but it can actually be quite dangerous to ride with. Typically it is a very simple fix and can be done with the turn of a screw. We highly recommend following our step by step guide on tightening your chain to see if you are able to fix it yourself before heading to a bike shop.

Robbie Ferri

Robbie Ferri

Robbie Ferri is a cyclist living in Norfolk in the UK. From breaking World Records to competing in some of the hardest Bikepacking races in the world he is not shy of riding the miles. He has been lucky enough to work at some amazing shops and with some big cycling brands. Alongside this he even had input in designing bikes and has also been a tester for unreleased products. He absolutely loves cycling and believes everyone should have a bike.