a chain
no it is a lever
Bicycle chain
bicycle
A bicycle designer uses maths to work out the frame angles, and the gearing. The number of teeth on the chainwheels, sprockets (cassette), chain length, and so on, all depend on maths.
pulley
It protects the chain from rain and road grime and it protects your trouser legs from chain gunk.
To fix a broken chain on your bicycle, you will need a chain tool to remove the damaged link. Then, you can reconnect the chain by inserting a new link or reattaching the old link using the chain tool. Be sure to properly adjust the tension of the chain before riding again.
To fix a chain that has come off your bicycle, you can carefully place the chain back onto the gears and sprockets. Use a chain tool or your hands to guide the chain back into place. Make sure the chain is properly aligned and tensioned before riding again.
The chain is wrapped around a cogwheel, which could be described as a pulley.
Chain fixers can help improve the durability of bicycle chains by repairing any damage or wear on the chain, ensuring that it functions smoothly and efficiently. This can prevent further issues and extend the lifespan of the chain.
A deraileur is the device that shifts the chain to different cogs on a bicycle.