Be Good to Your Chain
You've probably encountered fellow riders touting the pleasures of riding in all kinds of weather. They lie. No one likes riding in the rain. But if you ride long enough, despite your best efforts you will inevitably find yourself in this situation.
When you're done with the ride, the first thing you think of is getting dry. After a warm shower and dry clothes, you're good. You will suffer no lasting damage.
You tend to forget your faithful steed that carried you through this mess. Fact of the matter is that you will dry, but there, alone, in the garage, your poor bike is silently rusting. Rust is a phenomenon common to carbon steel. No worries, you say, my bike is made out of space age materials that don't rust. This is generally true except for one key component: your chain.
If you leave your wet bike unattended, you will inevitably come down to it the next day to find an orange patina on the chain, i.e., rust. Here's what I do to avoid this.
The first thing is to put the bike in a stand and spin the pedals backwards vigorously. This will fling off most of the surface water. I spin the wheel 100 times, not for any good reason except we engineer types like counting things. Next I wrap a paper towel around the chain and spin it again. Our former house cleaner used up half a rain forest's worth of them each cleaning day, so being a frugal Yankee (New York Yankee that is) and environmentally conscious I would fish them out of the trash when she left. Consequently, I have a lifetime supply of slightly used paper towels. Applying the quicker picker uppers will give you a pretty good idea of just how dirty your chain is (or was), before your ministrations).
The Coup de Grace is giving your chain a blow dry. For this I use an old hair dryer of Susan's. Set it on high and blast away for a while. Ideally you should do this until the chain is warm to the touch but I usually don't have the patience.
You're not quite good to go yet. You've got most of the moisture off by my now, but it doesn't take much for rust to rear its ugly head. What I do now is lube that chain. You can use WD-40. This is not really a lubricant, I'm told the WD stands for "water displacement" which is what you want. Using a real lube is good to keep things spinning, but will collect dirt. You want to get the lube into the links, but try to get rid of the excess on the chain plates (more paper towels).
If you let it go too long (which I usually do) you will find an accumulation of crud on the derailer pulleys. I had one that was so bad you could barely see the pulley teeth. To fix this, put a knife on the pulley and spin backwards. You should put some newspaper underneath to catch the nasty black crud projectiles. This is very satisfying.
Do this religiously and your chain will thank you.