I'm currently on a mini-tour round the Alps. Yesterday morning while coming down a poorly-surfaced road, I discovered I had no rear brake authority at all. No immediate harm done, so once we were off the mountain I headed off to the nearest motorrad dealer (Bayard Moto in Gap), a not unpleasant 50m ride to the west. Given that I arrived at 4.30 on a Friday afternoon, they couldn't have been more helpful - the tech replaced the rear brake fluid, and his explanation was that repeated use of front brake only causes air to build up in the rear brake system. This would make sense in that virtually all of my miles are road miles and given the linked brakes, I rarely use the rear brake lever - but how can this actually happen? ie how can air somehow get sucked into the rear brake system? Bike has done about 14k miles, serviced on schedule with front pads in Feb and brake fluids changed in Nov last year. Anyone ever heard of this?