I want to change out the back tire on my 82 cm250. What I´m wondering is if I´ll need to buy a new wheel/rim or if a wider one can be successfully and safely put on the existing rim which currently has a 120/90 16 tire on it. Also, I´m wondering if it´s even possible to put a wider back tire on the bike without it hitting the chain or other things. Does anybody know anything about this? Thanks.