What Size Bike Chain Do I Need?

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Bike riding is one of those notoriously simple and enjoyable activities of modern life.

If something is really, truly easy, for example, we can say that it’s as simple as riding a bike!

One basic consideration to take into account as you prepare to get riding is chain size. 

If bike riding is simple, bike maintenance is another thing completely.

A bicycle is a complex tool and serious riders know that the ride is more enjoyable if you have some knowledge of the machine itself.

The overall health of your bicycle, and the relative enjoyment you gain from riding it, derives from a number of different mechanical standpoints.

You’ll want to know before you buy your bike that it's the correct size for your body.

Then once you're up and running that your break wires are all in place, all the gears are running smoothly and that the chain is well-oiled etc.

Size Matters

What sort of impact does chain size have on overall ride-ability? How do I know that my bike has the right chain size at the moment? Is it expensive or cumbersome to alter my chain?

All good questions, all of which are answered below.

The Basics

Whether you have a fixed gear bike, a classic eight gear or a 20-speed monstrosity you’re going to need a chain that is the correct size for your bicycle.


The chain is arguably the most important mechanism in the bike. It links the gear shaft with the rear wheel and makes everything function.

Without the chain, or with a chain that is too loose or too taut (too short or long), you’ll either be completely stationary, plagued with mechanical problems, or in danger of experiencing a serious accident.

Let’s start with the first scenario: a chain that’s too tight.

How do you know that your chain is too tight?

This sort of diagnosis usually needs to be made by a professional but there are a few ways you can look into it on your own.

First, take a rag and probe your chain a bit.

If your chain is too tight you’re going to notice a lack of give as you probe it.

What’s the danger of having a chain that’s too tight?

What Size Bike Chain Do I Need - broken todaysbike

It might not seem like a big deal but having a chain that’s too tight can be extremely dangerous and can put you into a tricky situation quite quickly.

The biggest danger in this situation is that the chain will become so taut that it can’t handle the demands the rider is placing on it and it breaks.

This is extremely dangerous for obvious reasons.

If you’re pedaling along at high speed, even 15 or 20 mph, and suddenly experience a lost chain, you might find yourself flying over the handlebars or off the road.

Experienced riders know what I’m talking about; you do not want the sudden loss of resistance in the pedal shaft.

This may shift your centre of gravity forward and send you over the top.

That won't end well and could mean a trip to the emergency room.

As an aside you also might want to consider wearing a helmet but we'll cover that another day.

A Loose Chain

If your chain is too big (and thus too loose) on the other hand, you’re not actually in a whole lot of danger.

A loose chain can be diagnosed the same way an over-taut one can – by probing the chain with your finger.

A chain that’s too loose will have more than a small bit of give to it and might feel more like a loose string than a crucial mechanism.

Again, you’re going to want to put a rag on your hand as you feel around the chain in order to avoid getting grease on your fingers.

The other way to self-diagnose an ill-fitting chain is to look for certain cues while riding.

If your chain is too loose, for example, you’ll notice a delay and a large amount of slack when you run your pedals in a counter-clockwise direction.

You can feel an over-taut chain while riding, too, though that will feel a bit different, and it’s very hard to detect.

A novice rider may have a hard time noticing an over-taut chain just by riding his/her bicycle.

Be Safe Out There

In any case it’s important to treat one’s bicycle like the complicated machine it is, especially if you’re a novice rider.

Don’t be afraid to take your bike into the shop for a tune-up.

The mechanics will set you up nicely and will let you know if you have any more serious problems with your ride, like, for example, if you have an ill-fitting chain.

Happy riding!

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