Modern bottom brackets use a sealed bearing type construction that keeps water and debris locked out, so they seldom go wrong. Maintenance is impossible so they need replacing when they do wear out. Older style cup bottom brackets need to be re-greased every now and again, and occasionally will need to have their bearings replaced. There are a lot more teeth on the chainring cogs than those on the rear cassette, so need changing less regularly. Cranks usually a solid one piece construction so there is not much to go wrong.
More than any other tool in the kit, a reliable lever makes changing a tire easier, especially if you have road bike tires, which are difficult to remove. However, throughout testing, levers seemed to be the one item more prone to failure and poor design than anything else. For example, I found a random orange lever floating around my basement and I threw it in the test pool for fun—it seemed solid enough … until I began prying at the rim of a tire. It bent directly in half, slowly and smoothly, like taffy, and then was boomerang shaped forevermore.
But before I get started, let me share with you a few tips. OK, one tip: Get a work stand. Because putting your bike upside down isn’t good for it—yes, I said it. When I first started fixing my own bikes, I couldn’t afford a fancy $300, folding, magnetic, fixes-the-bike-for-you stand. I tried piecing together a “DIY $30 Stand.” I followed all the directions that the Internet demanded, and once I’d bought all the clamps and pipes, this thing cost really more in the neighborhood of $60—but it only stayed upright with a rope tied to something sturdy in the garage. It was one word: junk. So I bit the veritable chainring and charged a decent stand on my credit card (I hate debt, folks).
Don’t rely on others. “People need to recognize that now there are different cassette sizes, so there are different chains depending on what gear you have. A lot of people are like, ‘Oh my friend is always prepared they always have the stuff, I’m not going to bring anything.’ All of the stuff now is very bike-specific, and you have to have your own package of stuff.”
Whether you ride a single, 7, or 10 speed bike or anything in between, you will need a slightly different chain. The major difference is that they come in varying widths to accomodate the different spaces between the gears, but quality of construction is also a factor in choosing a chain. Inspecing the chain should be a part of your regular cycle maintenance procedure- It’s important to keep a chain well lubricated, but oil will also attract dirt and so different oils for specific riding conditions are available. Remember to clean your chain regularly to get the longest life out of it and the gears.