In 1888, Scottish inventor John Boyd Dunlop re-invented a type of tire which was filled with air. This made safety bicycles more comfortable. Soon, the freewheel was invented. This was a device inside the hub of the back wheel that allowed the wheel to spin even if the rider wasn't pedaling. However, this meant the rider could no longer stop the bike by backpedaling. As a result, better hand brakes were invented, and a different type of brake which could stop the bike if the pedals were turned backwards. Later inventions included better brakes, and gears which made cycling over hills much easier. During this time the bicycle became very popular. 