Originally Posted by
Mr IGH
Front fender with flap will help as will a chain guard such as an SKS Chainboard. Not perfect but much better esp for the rider.
There's a company called Bibia that makes mud flaps that do an amazing job of controlling spray and debris coming off the tire, I got mine on e-bay. There's a metal strip molded into the rubber that you just bend around the fender to mount it, no drilling or hardware needed yet very secure.