On a wide, gravelly mountain road, earth-coloured dwellings in the background, small boys scamper behind tyres of different thickness and circumference, beating them onwards with a stick. A donkey brays in sympathy. The thin, flexible tyres of bicycles are the hardest to keep upright, especially when performing turns (slowing and tilting the rubber hoop without loss of momentum) before racing back, sometimes in competition with another, cheered on by their companions, towards the starting line.