on paper, it is every 10,000 km. Other than that, you may swap the tyre positions especially you have negative camber settings to balance out the tyre wear.
Actually i dun go shopping for car parts...
recently i see a fren's (not close) car...underglow is quite nice...
not like ah beng type wan...
looks exactly like 2 fst 2 furious wan...
normally when you put underglow...