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.
A good patch will stick to your tube enough to keep air from leaking out. A great patch will act like a second skin and actually strengthen the tube where it’s applied, flexing and stretching with the tire. After 36 hours of testing, our official endorsement goes to the Rema TT 02 Touring Repair Kit. Its patches do everything other patches do, just better. The edge of the patch is also ruffled, which provides more edge surface area to bond—that’s a good thing.
Many bikes, including older models and track bikes, have bolts attaching the wheels to the frame instead of quick-release levers. If your wheels are bolted on, in most cases you’ll need a 15 mm wrench to remove it. We didn’t test wrenches, because there aren’t that many tiny 15 mm wrenches, but the GearWrench 15mm 12-Point Stubby Combination Wrench is perfect for stuffing into a flat kit and Amazon reviewers seem to think the same. Our experts also recommended the Surly Jethro Tule, but it’s expensive and harder to find.
As you mentioned, it is surprising how often you can get multiple flat tires on while riding, particularly on longer sprints. The tip about bringing a patch kit in your bike repair kit can be incredibly helpful if you’ve already had one flat tire. I agree that all you listed seems like an awful lot to carry, but it’s always better to be safe than sorry, isn’t it?
In addition to the Rema patches, put a new tire tube in your kit. The best method for dealing with a flat roadside is to swap out the tube and save the task of patching for later. If you’re not sure what size your tires are, it’s printed on the sidewall of the tire. This inner-tube buying guide has some photos of where to look. What brand is almost irrelevant as many tubes get manufactured in the same place, so whatever your local shop has behind the counter for under $10 will work fine. The only reason to spend more would be to save weight.
We spoke to a broad spectrum of cyclists—from a pro racer to a bike messenger turned mechanic to a touring cyclist who has logged thousands of miles throughout Europe—to find out what items they find indispensable. We sorted through 40 tire levers, almost 30 different kinds of patches, 120 different hand pumps, and 57 seat bags before we narrowed our choices for testing. And then we changed and patched tires more than 50 times, using four different bikes, five different wheels, six different tires, and almost 10 different sizes of tubes. After 96 hours of combined testing, we agree these essentials are some of the best you can buy.
If you’re going to use the chain whip you just made, you’ll also need a way to get that cassette off. A lockring remover is a must-have; unless you use one of the shady removal methods I’ve seen on the internet—which I wouldn’t necessarily recommend unless you don’t care much about the condition of the wheel after you use them. I recommend Park Tool’s iterations here that cost about $6, but you’ll need to buy the specific one for your brand/type of cassette. (By the way, I’m assuming you already have an adjustable wrench laying around somewhere to use with this tool. If you don’t, well, you’ll need one of those too.)
Patch kit:   Patch kits are easy to use, light and compact, and if you get more than one flat on a ride (it happens more than you’d expect), it can save you when you’ve already used your spare tube.   Plus, on a rear wheel, patching a tube can be faster than replacing it, as you can often do this without removing the wheel at all.  Another upcoming post is going to show you how to patch a tube.
Broadly speaking there are two major wheel sizes – 700c for road bikes and 26 inch off-road wheels. However there are a whole variety of older, less common wheel sizes and of course fold up bikes have much smaller wheels altogether. Repairing a puncture is not an emergency! It’s a basic procedure that every cyclist should be able to to perform, but doing it correctly involves more steps than many people realise. Wheel building is often seen as the most artful skill in bicycle maintenance, and separates the professionals from the amateurs but that doesn’t mean you should consider it out of reach. Truing a slightly misaligned wheel is a cycle maintenance job that almost any cyclist can perform.