The sound of metal rubbing against metal when you pedal is your chain grinding against your front derailleur. It’s a good indication that your chain is at a bad angle because of poor gear selection or you have not trimmed your gear selector.
Take a look at the arrangement of gears on your bike. At the pedalling end of things, you’ll have two or three big sprockets known as chain rings. The smallest chain ring is closest to the bike.
Sitting close to the chain rings is a curved bit of metal through which your chain runs. This is the front derailleur. It shifts the chain from one chain ring to the next and back again.
On the hub of your back wheel you’ll have a cluster of smaller sprockets – anywhere from six to ten of them. The largest sprocket is closest to the bike.
Notice how the small chain ring on the font lines up with the biggest sprocket on the back? That’s your easiest gear. Something like this is great for getting started at the lights with a full load of shopping or a small passenger, and riding up steep hills.
In the same way, your big chain ring lines up with the smallest sprocket on the back. That’s your highest or hardest gear. This is just what you need flying down a hill or sailing along with a tail wind.
Good gear selection means that you keep that chain as straight as possible. When you need easy gears, make sure you’re in the middle or small sprocket and one of the biggest sprockets. When you’ve got a full head of steam up, make sure you’re on the middle or big chain ring and one of the smaller sprockets.
Why all this fuss? Riding a straight chain prevents unnecessary wear on everything your chain comes into contact with. It can save you money and extend the life of components.
On hybrid and mountain bikes you only have three stops for gear selection. On road bikes, you can “trim” the front derailleur. A half click up or down moves the front derailleur sideways just enough to give the chain room to pass through.
That grinding noise just says: “Hey, we could do this more comfortably!”
See you on the road soon, God willing.