Recently, people have begun to think about the tool they bring along (you do, right?) on a ride to re-inflate their tires. For years, it was either a hand-pump or CO2. Roadies traditionally did the pump and MTB riders CO2 but roadies started using CO2 when frame pumps stopped fitting in modern frame designs. But with the introduction of electric mini-pumps and some newer, manual pump options, many people are reconsidering their choices. This post is a guide to how I recommend approaching the options. Top rule: If you aren't prepared and able to call for a ride home, always carry SOME sort of inflation tool Quick guide: How to choose a pump type: Where/how do you ride? If you usually have at least the option for a 'call of shame' to get home, all options are on the table. If you frequently ride in the boonies, though, a manual pump is mandatory. It is the only option that will get you home with repeated flats nearly every time. CO2 only works for how many cartridges ...
Once upon a time, chainrings were only a little complicated. You typically had 4 or 5 holes of some common measurement apart. Teeth were approximately the same and if they fit, they were fine. But with newer cranksets and chainrings, there are more options, and I see people get confused. I am sure there are some more systems out there than I'm listing, but here are a few: Conventional Bolted Rings These have been used for decades. The chainrings use some number of bolts to mount to the spider of the crankarm. The critical dimensions are the number of holes and the diameter of a circle that passes through them all. If your old one is not labeled (or the crank isn't) you need to measure and that can be complicated. Measure BCD on 4 Bolt (Source: Wolftooth) 4-bolt patterns are easy, whether symmetrical or not. Just measure across an opposing pair. In theory, you're measuring the centers of the holes, but edges on the same side is usually easier. That distance IS your BCD. 5-...