Lifting my bike out the tight fitting car boot this morning, heard a metallic ping sound - thought, oh no! broken spoke. Checked them all, but no damage, then rea\lised that I have absolutely no front brake at all. The (mechanical) brake is a Tektro IOX, the lever seems to move the actuator arm instantly, and through its entire range, and the outer pad seems to move ok. Any ideas warmly welcomed. I have never fitted, opened up, or serviced a disk brake, and dont really know where to start. Would hate to make things worse !!!