Abstract: Sulfur containing organosilicon compounds having the formula:Z - Alk - S.sub.n - Alk - Zin which Z is: ##STR1## where R.sub.1 is alkyl of 1 to 4 carbon atoms, cyclohexyl or phenyl and R.sub.2 is alkoxy of 1 to 8 carbon atoms, cycloalkoxy of 5 to 8 carbon atoms or alkylmercapto of 1 to 8 carbon atoms, alk of a divalent aliphatic hydrocarbon or unsaturated aliphatic hydrocarbon or a cyclic hydrocarbon containing 1 to 18 carbon atoms and n is a whole number from 2 to 6 are used as reinforcing additives in rubber mixtures containing a silica or silicate filler, and in a given case carbon black; the organosilane is coated on the surface of the silica or silicate filler particles.

Abstract: Sulfur containing organosilicon compounds having the formula:Z -- Alk -- S.sub.n --Alk -- Zin which Z is: ##STR1## where R.sub.1 is alkyl of 1 to 4 carbon atoms cyclohexyl or phenyl and R.sub.2 is alkoxy of 1 to 8 carbon atoms, cycloalkoxy of 5 to 8 carbon atoms or alkylmercapto of 1 to 8 carbon atoms, alk of a divalent aliphatic hydrocarbon or unsaturated aliphatic hydrocarbon or a cyclic hydrocarbon containing 1 to 18 carbon atoms and n is a whole number from 2 to 6 are used as reinforcing additives in rubber mixtures containing a silica or silicate filler, and in a given case carbon black; the organosilane is coated on the surface of the silica or silicate filler particles.

Abstract: A vulcanizable rubber mixture for tire treads containing a rubber, preferably vulcanizable with sulfur, silica filler, plasticizer oil, a sulfur containing organosilane, sulfur and an accelerator comprising one or two polybutadiene rubbers in an amount of 20 to 100 weight % of the total elastomer, one or two rubbers other than a polybutadiene of the group consisting of synthetic rubber and natural rubber in an amount of 80 to 0 weight % of the total elastomer, plasticizer oil in an amount of 40 to 100 parts by weight per 100 parts by weight of rubber, at least one bis-[alkoxysilylalkyl]-oligosulfide in an amount of 0.1 to 25 parts by weight per 100 parts by weight of rubber, sulfur and/or sulfur donors in an amount of about 0.2 to 8 parts by weight per 100 parts by weight of rubber, and at least one vulcanization accelerator in an amount of about 0.