rubbering in

rubbering in
 n.— «Tires were taken to the speedway for the race that Grant said were identical to the setup that was tested, and Pemberton said Friday’s practice session went normally. But it became apparent Saturday that the abrasive track was not building up a layer of rubber, a process called “rubbering in.” It usually occurs during practice sessions and lower-tier races, and it improves grip, leading to longer tire wear, Grant said.» —“Nascar Considers Changes After Tires Deflate a Race” by Dave Caldwell New York Times July 30, 2008. (source: Double-Tongued Dictionary)