If you own a pair of capri pants that are comfortable to cycle in, but you don't like the way the bottoms flutter in the breeze or get caught in the drivetrain, then here is a quick and dirty way to turn them into cycling knickers:
You will need a long elastic band, which can be purchased at a shop that sells sewing supplies. Alternatively, you can use narrow hairbands, as shown above (these come in a pack of 10 that costs around $2).
Check the hemming at the bottoms of the pant legs. Sometimes the manufacturer will leave an opening in the hemming, at the outer seam. If not, carefully create an opening. Don't cut into the actual fabric; just undo a small portion of the outer seam through which to thread the elastic. This was a quick and whimsical project, and I do not have a step-by-step photo documentation. But I hope these after-the-fact pictures adequately demonstrate what is involved.
Once you have threaded the elastic through the hemming, simply tie it on the side so that it is snug, but not constricting. You can then choose to either hide the knot inside the seam and sew it back up, or leave the knot exposed. The benefit of the latter is that you can keep converting the pants back and forth between normal capris and cycling knickers.
Aside from staying clear of the drivetrain, an additional benefit to these knickers is that you can continue to wear them in colder weather. Simply add long socks, and the elasticised bottoms will protect your legs from the wind. Cape Cod has greeted us with temperatures in the 50° F range, and it looks like I will be living in these for the next 2 weeks!