Keychain style flashlight or headlamp, LED type, not incandescent: The keychain style is tiny and lightweight, the headlamp style is a bit bulkier but easier to use. You can get these for a couple of bucks or less at the local big box hardware store. The LED ones are lighter, more durable and last considerably longer. Very useful if you need to make a repair after dark! I keep a keychain style one as a backup as I normally have a headlamp in my backpack.
Otherwise, this tool should serve the average commuter well. Specifically, we think you’ll find the size 4, 5, and 6 hex keys, extremely common sizes in bicycles, very helpful. They’ll adjust seat-post heights or let you remove the saddle entirely, or tighten a loose stem that’s always rattling apart. The Phillips head will tighten loose bolts on shoe cleats or the rear derailleur. The most common use for the torx would be adjusting disc brakes if you have ’em.
Writer Peter Flax, the former editor-in-chief of Bicycling magazine, rode over 1,000 miles and tested 15 tools for our full-length guide to multi-tools, and he concluded the Topeak Mini 9 is the best for casual cyclists. It’s tiny, it’s light, it’s easier to get some leverage with than other tools that have different designs. It’s not meant for serious wrenching on your bike, but it’s good for on-the-fly adjustments.
The best type of bike for exercise depends what level of rider you are and whether you would rather ride on trails or on the road. There is a type of road bike that is called a “Fitness Bike,” and features a lightweight frame and narrow tires, but do not have a drop handlebar. This may be the best type of bike for someone who intends to ride regularly and strenuously on the roads. If you plan to do a lot of trail riding, the best bike for exercise would probably be a mountain bike. For a person who uses bikes for transportation and exercise, but doesn’t go off-road, the hybrid bike build is a good type of bike.
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.