What size are the rx2s, if you want to keep the same speedo ratio the tyre size will depend on the wheel size, a rule of thumb is if you up in size 1" you reduce the sidewall by a profile to keep overall rolling circumference about the same ie 205/50/15 , 205/45/16 , 205/40/17 If you have the wheels the best way to see if they will clear is to have a go at fitting them, even if no tyres you'll get a somewhat good idea of the clearances and you'll definitely know if they clear the brakes