On a geared bike, the derailleur springs usually take care of chain tension for you. But fixie bikes or single speed bikes don’t have a derailleur. As a result, some DIY chain tension adjustment is sometimes required.
The importance of getting chain tension right is not to be underestimated. It can affect cycling safety, bike maintenance and how much enjoyment you get from your ride.
The importance of chain tension
Chain tension is important because, if you get it wrong, you could end up facing one of the following problems.
Your chain falls off
If your chain is too loose, it could fall off the cogs whenever your bike takes a knock or if you’re riding over bumpy ground. You then have to stop and faff about with the chain before you can continue your journey.
Parts become worn
When a chain is too tight it puts extra pressure on bike parts. Additional friction and excessive force will cause unnecessary wear and tear. This means you’ll spend more time and money than you need to, replacing bike parts.
It’s harder to ride
Whether your ride is interrupted by a chain that keeps slipping, or whether you’re having to pedal harder to compensate for the friction your chain is causing, poorly configured chain tension makes for a frustrating ride.
A quick note on gear ratio
On a single speed bike, chain tension doesn’t technically affect gear ratio.
Your ratio is dependent upon the number of teeth in the rear sprocket in relation to those in the front chain ring.
Nevertheless, if your chain is too loose or too tight, this will affect how it feels to ride your bike. Particularly if your chain is too tight, you may feel that you’re riding a harder gear setting than you actually are.
You can learn more about the best ratio for a single speed bike by reading our blog post on the topic.
What is the ideal chain tension?
So now we know the importance of chain tension, how can you tell if your bike chain is set up correctly?
Simply take a look at your chain and give it a wiggle. You should be able to move the chain up and down by about half an inch / a centimetre.
More or less give than this and you need to make a tension adjustment.
Parts tend to give a little once a bike is in use. So it’s wise to check chain tension after you’ve had your bike for a month or two.
What to do if your chain is too loose
We’ve already written a pretty comprehensive post on this topic. So you can see more details on how to tighten a single speed bike chain here.
But let’s take a moment to recap the basics.
You’ll need to grab a spanner from your bike tool kit and flip your bike upside down.
Next, loosen the rear wheel axle nuts, stand at the back of the bike and pull the rear wheel towards you. This tightens the chain.
When you’re happy that you’ve achieved the desired tension, tighten the axle nuts back up again and you’re good to go.
What to do if your chain is too tight
If you end up pulling your chain too tight, simply reverse the process described above.
Loosen the rear wheel axle nuts, stand at the back of the bike and push the rear wheel away from you. This will loosen the chain.
How to get chain tension right when replacing your chain
All chains need replacing from time to time. If you’re going down the DIY route, rather than taking your bike into a shop, then here’s what you need to do to achieve the right chain tension.
First, you need to take off the old chain. Some chains have a quick release link. For others, you’ll need a chain tool.
If you were happy with the tension of your old chain, lie the old chain next to the new chain, matching them up rivet for rivet.
New chains are usually longer than they need to be. So use a chain tool to remove links and cut the new chain to size.
Lie the chain over the rear cog and front chain ring. Join the ends. Then use pliers to push the pin into place and secure your chain.
If you feel that your chain is still a little too loose or a little too tight, loosen the rear wheel and push or pull accordingly.
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