Change and a $20 bill: In case your cell phone’s battery dies, it’s nice to still be able to use a payphone if you need to. Also, the $20 is a great thing to have in case you lose your wallet or have some other mishap. I’d rather be able to sit in a coffee shop or fast food restaurant when it starts raining while I’m waiting for my friend or cab ride, and a hot cup of tea or coffee or the beverage of your choice and a snack makes it all the more pleasant. Just try to remember, this is for emergencies, and if you use it, replace it ASAP!
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).
Now you might be wondering: “I’m carrying a tube; why carry patches at all?” As insurance for the unforeseeable. Wirecutter senior editor Christine Ryan admits she didn’t use to pack them, but said, “I’ve regretted that decision when I’ve had a flat on a ride, used my spare tube, and then, half an hour later, had a second flat. Also, lots of people aren’t very good at figuring out—or don’t take the time to figure out—what caused their flat and remove the cause: thorn, eensy bit of glass, whatever. Then they promptly have a second flat, and everyone else laughs at them.”
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.