there's the same problem with bikers (ie dirtbikes) and mountainbikers. There has been quite a few instances of dirtbikes using MTB trails especially at Glentress near Peebles. We're (mtbers)asked to report them but there's really not much anyone can do as it's open forest. Saying that we use downhill tracks that the dirtbike boys have created, but the MTB forest trails are designed for just that- mountainbikes. They'll not take the hammering that the dirtbikes give em.