Silica is a filler derived from sand that is used in the rubber compound of a tyre tread. Because of its excellent low rolling resistance, it is very commonly used in energy-saving or fuel-saving tyres. Tyre compounds featuring a relatively high amount of silica will also have excellent wet weather performance. For this reason you will often find winter / rain tyres developed with silica compounds. Most modern tyres will, with varying degrees, have silica included in the compound.