Being a professional bicycle mechanic (as well as a Triathlon Coach), I’m often asked what the most common problems are that I see with bicycles.
These would be poor gear shifting, “honky” disc brakes, worn bottom brackets (the bearings at the bottom of your frame that the cranks spin around on), worn or loose headsets (the bearings that your handlebars and front wheel rotate on) and a worn drivetrain.
In this blog, I’m going to write about a worn drivetrain as it could potentially save you upwards of £200 and keep your bike running nicely. Watch this space for more blogs about the other mentioned common problems.
Most people don’t regularly check their chain for wear and ride their bike until something starts to make a noise. They take their bike to a bike shop who tells them their drivetrain is worn out and it will generally cost upwards of £250 to replace everything.
Your drivetrain consists of the chainrings (the big toothed rings in the middle of your bike that are fixed to your cranks and that the chain goes around), the cassette (the cluster of smaller toothed rings on your rear wheel that the chain goes around) and the jockey wheels (the small toothed wheels in the rear derailleur).
So, what does a worn drive train look like?
The easiest way to see is to push down on your cranks whilst holding your bike stationary and look to see if the chain starts to “lift” off the front chainrings.
If you look at this picture, you can see the blue frame between the chain and the teeth of the chainring.
There should be no visible gap (like in the picture below) where new chainrings and a new chain have been fitted.
If you can see daylight or your chain starts to lift, then you’ve left things too late. Your chain has worn out and no longer sits nicely on the teeth of the chainring and will eventually start to slip off the teeth of the chainring – usually when you stand up on the bike to put some power down such as going up a hill. This is bad and usually result in you falling forwards either landing on the top tube of the bike, on the floor or both.
The bad thing is that because everything is so worn, you CANNOT fit a new chain. The old worn chain has cut a new profile into the teeth of the chainrings and this new profile will not match the shape of a new chain. Unfortunately, the same will have happened to the cassette at the back of your bike and the often neglected jockey wheels as well.
The only real solution is to replace everything – the chainrings, the cassette, the chain and the jockey wheels and to ensure this all works smoothly, you need to change your gear cables (inners and outers) as well.
Here’s the money saving solution – buy yourself a chain checker (usually less than £10).
When your chain gets close to 1% wear (according to your chain checker) change the chain – most chains are around £25. This will prolong the life of the rest of your drivetrain and save you a potentially big bill.
If you’re chain is already over 1% stretched, then check to see if your chain is lifting – it may already be too late and a full new drivetrain is the only real solution.
Happy and safe cycling,
Coach Pat.
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