I am a keen mountain-biker, and was the proud owner of a fairly expensive mountain bike. My bike was fitted with 'V' brakes, which are extremely effective, though prone to squealing. My dear brother decided to have a ride on my bike one day, while I was out. He noticed the squealing as he cycled down the hill we live on, towards the invariably busy crossroads at the bottom. Being a helpful sort, he headed back home and proceeded to pour a generous amount of 3-in-1 oil onto the brakes, before once more setting off down the hill. The oil worked! The only reported squealing came from my brother, as he slammed into the side of a moving VW Beetle. To this day he sports an impressive scar running from his eye socket to just past his ear.
