There is a product that soften the tyres of the 60 class

“Yes, there are additives that can be sprayed on the body which soften the mix. The process these products trigger is very simple: they make the vulcanization regress by breaking the molecular bonds of tyre polymer. Essentially, they the tyre returns to its previous machining state: vulcanization closes all the molecular bonds, thereby hardening the rubber; when they are reopened, the compound remains soft and has more grip on asphalt. They are obviously not only used for class 60 tyres, but for all classes. Even though they are forbidden. One of the reasons Federations try to use softer tyres is to prevent the use of these products, since it is more difficult to “fix them up”. But that’s not all, because there are shards that mix resins with solvents, to form a paste that is then coated onto the tyres so as to create a kind of glue on the tread…”.