Any bike that gets ridden seriously as transportation or on long rides needs at least a basic tool/emergency kit, and the knowledge to use it, unless the rider is always in a position to call a friend with a car or a cab when their bike needs a quick fix on the road. If you never travel more than a few miles, this can be overkill, and calling a friend or a cab may be just the ticket, but if you want to be more self reliant, this is something you should seriously consider. This list may sound like an awful lot of stuff to carry, but really, it only weighs a few lbs and fits in a small, under-seat bag that comes off quickly so I don’t have to leave it with the bike if theft is a concern. If you always carry a regular rack top bag, you can also just put all this in a small nylon bag and throw it in there, but I prefer an under-seat bag.
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.