"If a new tyre is punished too heavily, too quickly, its critical tread compound temperature may be exceeded and blisters will appear and burst...Heavy cars, unsympathetically-driven cars and badly set-up cars may burn-out their tyres (particularly at the front) in a less abrupt manner. This phenomenon, known as 'graining' or 'feathering', rolls little pieces of rubber off the tread - diminishing its grip. A watchful driver will recognise the condition as one edge of his front tyres - or of the rears seen in his mirrors - will blacken. The car's cornering power will be limited and if he presses on the condition will worsen. A sensitive driver will ease off, roll-away the loose granulation, and after a few laps will see his tyres regain their normal appearance and will find much of their adhesion restored."
(Doug Nye, Motor Racing in Colour, Blandford Press, 1978, p44).