First, I researched. I looked at Amazon’s top-rated products and their user reviews. Then I consulted Bicycling magazine, Gear Junkie, Bike Radar, Outside, and the occasional bit by Lennard Zinn via Velonews. I also found some worthwhile discussions at Bike Forums. Then I spoke with four experts, Ramona Marks, Scott Karoly, Cari Z, and Alison Tetrick, riders from all across the spectrum, who tour, repair, and race.
Mountain bikers are in different world of repair entirely, one that borders on the comedic absurd. It includes large pumps designed to fill up big, fat tires that squish over things, and a medley of assorted slimes meant to be injected into tubes or tires. In that world, the number of days it takes you to fix your tire and return from the wilderness is a badge of courage—bonus points if you’re bleeding—and we’re guessing that’s not what you’re going for next time you set out for groceries.
Packed with basic tools, this compact tin rescues puncture-interrupted bike trips. Pedaling away to a picnic spot with a pal, you hear a disconcerting "pop!". Your two-wheeler is now down one wheel, and unless you've got mad unicycle skills, you need tools. Good thing you brought this handsome, compact tin. Just break out the metal tire levers and patch kit, and you're rolling along again in no time. The six-sided, dog bone-style hex wrench adjusts the most common bike screws and bolts and screws. Made in China.
A pair of disposable latex gloves: Not absolutely necessary, but good for keeping grease and grime off your hands during a repair. Also, nice to have in an emergency when it starts raining and the temperature drops 20 degrees and you don’t have a pair of regular gloves. Just keeping your hands dry and the wind from directly blowing on them makes a huge difference in comfort.
It has some useful information for basic repairs... not so heavy on the maintenance side but there is some in there. The pictures and drawings are in black and white, but mostly visible. Only a few are difficult to see. However, they are in 2-dimensions and they don't show you HOW to do the thing, they only show you the general area and the part you want to manipulate. The phrasing in the instructions can be hard to follow without a good visual reference unless you're already a master bike mechanic (which you aren't if you're thinking about buying this). So, buy this for general reference and rely on Youtube for video. The two together are better than either one alone.
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.