How do I put my bike chain back on if it falls off?

In an ideal world, your gears would always be perfectly adjusted, your drivetrain would emit a quietly contented purr, and the whole bike would be so well behaved it'd deserve a rosette.

Unfortunately, back in the real world, a combination of grime, chain wear and time-crunched lives with limited room for bike fettling all contrive to put a stick in the spokes of our perfect scenario.

Which all means unless you're exceptionally fortunate, you'll eventually find yourself standing by the side of the road or the track, looking at a bike with a dropped chain and wondering what to do next.

First off, if your chain falls off (also known as a dropped chain), it doesn't mean there's anything fundamentally wrong with the bike. It might need an adjustment here or there, or it might be simple bad luck – an unfortunate bump in the road at the wrong time, but very rarely anything more serious.

Let's put it out there from the start though: when your chain falls off, don't keep pedalling in the hope that it will find its way back on to the chainring or sprocket. A couple times out of 10 this might work out – the rest of the time it's more likely to mangle your chain, your components or your paintjob – or all three. Patience is a virtue here.

Additionally, when handling the chain, care of your fingers and keep them away from the gap between chain and chainring / sprocket teeth as you attempt to wind it back on.

In this article we're going to take you through exactly what to do when the inevitable happens, with the help of our expert Yousif Sadik, owner of the Bike Bros store in Guildford, UK.

Unfortunately, unless you go prepared, there's a reasonable chance that your hands are going to get dirty doing this – another good reason to keep your chain as clean as you can. There is a hack, however, that Sadik recommends: nitrile gloves.

"They're very small, you can just pack them in the rear pocket, and they're inexpensive," he says. "You can buy a box for about £10 ($12.50). The good thing about them is that they aren't right and left-specific, so you won't be left with 50 left-handed gloves, or whatever. Just stuff one or two in your pocket and go, and if you need to grab your chain or something, at least you have one – or even a pair – of gloves."

When it comes off the chainrings

One of the most common dropped chain scenarios occurs during a downshift from the large to the small chainring at the front, with the chain falling down the inside of the chainring/s.

"That's an easy one," says Sadik. "You just have to lift it up and put it back on. Pull from the bottom, and then just lift it all the way up and onto the top.

"It doesn't have to sit on there fully, if you're in a weird gear, or whatever," he adds. "But as long as it gives you enough to seat the chain. And then you lift the rear of the bike, and you just pedal through so the chain sits on."

The same technique applies to times when the chain drops off the outside of your front chainring, although this time you may find you have to squeeze the chain through what is often a too-small gap between chainring and front derailleur mech.

"This one can be a little more finicky," Sadik says. "The cage of the front derailleur may be a bit in the way. But it's certainly possible to squeeze it though – you just have to be a bit mindful of how to do it."

When it comes off the sprockets

On occasions your chain might come off the rear sprockets – either off the small one at the bottom, or off the large sprocket and into the spokes. This is where things have the potential to get trickier, and stopping pedalling as quickly as possible is of the essence.

Let's deal it coming off the inside first, and dropping between the smallest sprocket and the frame.

"If you didn't put a lot of power through it, fine, you should be able to, again, pick that up and put it back on," Sadik says. "I'd grab the chain from the top, lift it through.

"However, if it's stuck, which does happen more often than you'd think, you're going to just have to take the rear wheel off."

This will allow you to fish out the chain and place it back on.

"Inversely, if it's stuck behind between the wheel and the cassette [after coming off the biggest sprocket] it's a similar scenario. But if you're struggling to pull it out, you may need to take off the cassette, which if you're out for a ride may be a difficult one."

You'll be relieved to know that encountering a chain stuck so fast that it simply won't pull out from behind the cassette is unusual, but if it does happen, you might be able to reach a bike shop that can help out.

They will likely also need to adjust your rear derailleur for you, because it is usually only because of maladjustment of the limit screws (these stop the derailleur moving the chain beyond the end sprockets) that the chain will come off the rear cassette.

Correct adjustment of the limit screw at the spoke-side of the cassette is particularly important, because overshifting here can find the mech tangling in the spokes, bringing the lives of numerous components to a swift and catastrophic end.

Prevention is better than a cure

As you've probably already decided, it's a good idea to try to avoid a dropped chain if possible, even if only to keep your fingers (or nitrile gloves) clean. To this end, get your local bike shop to make sure your gears are adjusted as well as they can be – or do it yourself if you know how.

As Sadik says, "The ideal scenario is to make sure your bike is in order. You know, put it on a stand and go through it, make sure everything is in order, or take it to a bike shop."

Whatever happens though, equipped with your workshop gloves and the info in our article, you will hopefully no longer be left staring at a chainless bike at the roadside and wondering who will be least irate about having to come out and pick you up. Happy riding!