A bicycle must make a tradeoff among reliability, versatility, light weight -- pick any two, or some compromise among the three. Outside urban areas dense with bicycle repair services, any bicyclist will have to perform some common on-road repairs, or ride with a companion who can perform them, or call for a ride now and then. Even the simplest, most rugged beach cruiser bicycle can't offer the trouble-free service you would expect of a lawnmower, car or refrigerator. Still, the mechanical simplicity of the bicycle and the resulting ease of common repairs, performed with lightweight tools, allow bicycling to be a practical travel mode.
Other articles on this site give detailed instruction on repair tasks. This article includes links to those articles, and describes the tools needed to perform common on-road repairs. There is also good information in books and online.
Simple On-Road Repairs
There are certain basic procedures which any bicyclist ought to know:
How to remove and replace a wheel, covered in the article about fixing flat tires. This is important when transporting a bicycle, but also to replace an inner tube or a tire (though a punctured inner tube also can usually be patched without removing the wheel). Correct adjustment of quick-release assemblies on hubs is especially important for safety.
Basic wrench skills, to dissassemble, reassemble and tighten parts.
The On-Road Tool Kit
What tools should you carry with you, to get you home or to a bicycle shop.?
Stories abound of bicyclists who go on tour lugging 10 or 15 pounds of tools, ready to fix almost anything on their bicycles.
At the other extreme, a road racer carries no tools. The team mechanic follows in the team car, ready to supply a replacement wheel or entire bicycle as needed.
A reasonable toolkit for a more typical bicyclist weighs a pound or two and covers the most common on-road repair needs. The weight can be even less on a modern bicycle which uses exclusively Allen-wrench fittings. On-road tools fit into a small bag which straps to the underside of the saddle, or which can be carried in a pannier or touring bag.
A small tool kit allows a bicyclist to get rolling again almost every time something goes wrong. You might carry some tools which you don't need for your own bicycle, to lend a helping hand to other bicyclists who are stranded. That has been the start of many a beautful friendship!
Here's my preferred tool list:
Multi-tool -- the "Swiss Army knife" of bicycle tools, which includes several metric Allen wrenches, flat-blade and #2 Phillips (cross-head) screwdrivers and often a small socket wrench. The multi-tool provides a single, convenient handle for all of these tools.
Additional Allen wrenches which the bicycle uses and are not included in the multi-tool.
8-9-10 mm socket Y wrench.
Torx wrench kit (like a multi-tool) if your bicycle uses any Torx-head bolts (Torx wrenches are like Allen wrenches but with a star-shaped cross section),
Tools and supplies to fix flat tires -- pump, tire levers, patch kit, tire boot. For more details see the article on flat tires on this site. In case you can't find the leak or the inner tube is unrepairable, you might carry a spare inner tube. Replacing the inner tube can be faster than patching, too.
6-inch adjustable wrench if your bicycle uses nuts and bolts with hex heads -- and to straighten bent parts or lend a helping hand to another cyclist. See Sheldon's article on adjustable wrenches. The adjustable wrench also can remove and replace most pedals -- though many pedals also have an Allen-wrench fitting on the inner end of the axle. Keep pedal threads well-greased, because a 6-inch adjustable wrench does not have as much leverage as a purpose-built pedal wrench.
If your bicycle has a cassette, a Stein Mini-Cassette Lockring Tool (on-road cassette-lockring tool). You need to remove the cassette to replace spokes on the right side of the rear wheel.
Stein Mini Cassette Lockring tool
If your bicycle has a freewheel, you could carry a freewheel extractor, but then you will have to borrow the use of a vise or large adjustable wrench unless you are lucky enough to find the on-road tool which lets you use the handlebar stem. As I recall, this tool was made only to fit SunTour freewheel extractors.
Freewheel extractor holder with freewheel extractor
A few links of chain matching your bicycle's chain. If your bicycle has a 9-speed or higher Shimano chain, you will also need replacement chain pins and the tool to install one. If a SRAM or Wipperman chain, a spare master link. Best advice is to avoid more than an 8-speed systme iwth a Shimano chain.
Small bottle of oil
Spare batteries for battery-powered bicycle lights.