Next to everything else that might go wrong with a bicycle on an extended ride, a flat is a relatively minor issue that can be easily repaired trailside, if the right tools are at hand. If they aren’t, a quick fix can turn into a long walk. Well-prepared riders will perform a tune-up regularly and clean their bikes after every ride. For the less-diligent, a well-stocked repair kit will suffice.
Unlike floor pumps, most hand pumps do not have pressure gauges. To get readings during my original round of testing for this guide, I built a special rig involving simple hardware-store parts. But the experts I spoke to seem divided on the usefulness of gauges. Half thought they were unnecessary, added bulk, and drove up cost. Why do you need a gauge if you know 100 pumps inflates your tire? But the other half liked them, because the “thumb test” is notoriously inaccurate.
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.
Basic first aid supplies:  A few bandages of varying sizes.   6 Aspirin, or other OTC painkiller of choice.   A few alcohol pads in sealed foil packs, useful for cleaning grease off grease and grit off of the bike, and also cleaning cuts on yourself if you take a spill.  1 day supply of any prescription drugs you need to take regularly.   Wrap these up in tinfoil and tuck away.   It might just save your day.
2) On my second day, the pannier bag fell off and got lost after I stopped for lunch, which required locking up the bike somewhere, so I took the bag into restaurant and re-attached it using the two velcro straps on the rear rack. I've used many panniers before, thought I did it correctly. But apparently I did not. So I paid $55 (cost) to replace everything in bag and bag. In hindsight, I wished I'd put a bungee around bag straps to really secure it to bike. PROBABLY MY FAULT.
Friction gear systems are a lot simpler to adjust, because the movement of the derailer cable can be modulated as you ride, every time you change the gear- they require less cycle maintenance. Modern index shifting systems are a little more complicated because each ‘click’ must release the exact right amount of cable to allow the derailer to move the correct distance to move the chain from one gear to another. Setting up and adjusting a derailer is not difficult and requires only basic tools, but there is a methodical procedure to follow.