Standard inner tube for 30 - 3 1/2: Long Central Valve Model T Tube Heavy duty inner tube for 30 - 3 1/2: Central Valve H/D Michelin Tube 760X90 RET30 - 3 1/2 can also be described as: 30 x 3 ½ or 30 – 3.530X3.5 tyres were original equipment on the Ford Model TThe Ford Model T fitted 30-3.5 all round, however before 1918 the..