using a tube walla tyre dosent harms, but the problem is that c if the tyre is not wobling or bubling,
VItzs (99-04) orignal size 155/80/r13, CULTUS And Santro have the same tyre size. u can get Generals XP2000 for less then 2000 (these rates are old new rates may varry) each, i wud suggest change all 4 or change them as u are comfortable 2/2 kerke,