I have always realised that there was a slight warp on one of the disks. It was not bad but it was annoying. Well I finally replaced the warped disk with a second hand one and all is now well. Smooth as silk. At the same time I replaced all the pads. Many people complain about the braking performance of the standard set up. I change my pads at half worn and fully service the calipers every 2 years and I find the brakes fine. With no abs and poor road surfaces do I really want brakes that allow me to do a stoppy? Hell no!