The crank, chainrings, and cassette are the parts that transmit your power to the rear wheel. When I bought my bike, I couldn't care less for these components. I wouldn't mind to buy the cheapest transmission components. But thanks to the good advice from my bike shop's professionals, I don't regret having paid more for better equipments.
03_IMG_5213.jpg
Choosing proper chainrings and cassette are important for the kind of ride you plan to do. At first, I had no plan to climb mountain, I didn't know why anyone would bother with climbing mountains when there are plenty of flat roads. But now, I like the challenge that mountains offer. So, don't make the mistake here of thinking that you won't climb mountains. You don't know whether or not you would like it, not yet.
The chainrings are attached to the crank. The above picture shows two chainrings: the large one with 50 teeth and the smaller one with 34 teeth (50/34T). The 50/34 combination is usually called "compact". The standard chainrings usually come with 53 and 39 teeth. And one more choice would be the triple chainrings offering more possibilities when climbing steep hills. I personally find that I still have a lot of work to do before I can have enough strength to make good use of a 53T chainring. So when I was advised by professionals to start with a "compact" chainrings, that was a good piece of advice.
The rear cassette is usually composed of 10 speeds from 12-27T. You can also find manufacturers offering 11-28T cassettes.
The combination of a chainring and a rear sprocket would determine the gear you use. Low gears (small chainring + large sprockets) allow you to climb steep hills without forcing too much on your legs, but you can't go fast with low gears. High gears (large chainring + small sprockets) on the other hand allow you to go very fast.
