Here in the PNW, fenders are pretty much a necessity for any useful bike, and a mud flap is a necessity if you plan on riding said bike in the rain with other people behind you. After spending a few rides in the rain behind someone without a proper mudflap, you begin to understand...
Anyways, I'd constructed a mudflap out of a piece of the once-ubiquitous mouse pad, but it had a few shortcomings (namely, it sometimes got sucked up between my tire and fender after hitting a sharp bump or hole in the road), so I decided to try a chunk of detergent bottle. Here's what I used:
- razor knife
- detergent bottle
- adhesive-back velcro strips
Detergent bottle and knife in hand, I started hacking away:
Once I got it down to size, I threw a strip of velcro on the back, and was ready to go:
I think I might throw a coat of black spray paint on it, just so it matches any bike I put it on.
Some people might scoff at using velcro to attach the mudflap to the fender, but I've found that it holds surprisingly well. Plus, I don't have to drill any holes in my fenders, and when I inevitably come up with a better flap, it's an easy switch.