Rubber products with low heat build up on mechanical stressing

A process for reducing the heat build-up on dynamic stressing of vulcanised rubber products, which comprises admixing for this purpose, to vulcanisable rubber mixtures, mixtures made from non-selfcuring novolaks A as reinforcing resins and at least partially etherified triazine resins B as curing agents for these reinforcing resins, wherein the triazine resins B have a molar ratio of formaldehyde to triazine (F/T of from 0.5 to 5.5 mol/mol, having a ratio A/T of the amount of substance of alkoxy groups to the amount of substance of triazine in the triazine resin B of from the higher of (F/T−1.75 mol/mol) and 0.5 mol/mol, up to not more than 90% of F/T, and wherein the alcohols used for etherification are selected from the group consisting of linear and branched aliphatic alcohols having from 1 to 18 carbon atoms.