Soften Rubber Tire compound
Is there anything currently available to soften the rubber of old tires? I have a few set of brand new tires that are over 12 years old and would like to soften them a little to work better on blue-groove clay indoor tracks. I'd hate to not use them at least for practice.
There used to a way using mineral spirits or turpentine, putting onto the tires surface and then putting the tire in a zip lock bag but I have forgotten what exactly was used.