Polyurethane tyres were first developed during the Second World War, when German scientist Otto Bayer utilised polyurethane as a replacement for expensive rubber. But the world hat to wait until 1971 for this material to become an effective flatproofing solution. We know this solution as TyrFil, and this year Carlisle TyrFil celebrates the 50th Anniversary of its signature brand, the world’s first polyurethane tyre fill material intended to flatproof tyres.