i can only answer a few questions for you, some only through my opinion, british people Wheel Size Calculator are you asking for the brake pads ? or a bigger brake disc ? if pads obviously no, you dont need them, unless they're worn out brake disc wise, im not too sure if it will affect it majorly, but in my opinion you dont need it, as far as my knowledge goes for getting bigger brake discs, its purpose is to offer better stopping performance, its like newtons third law, for every action there is an equal and opposite reaction, if you go fast, you gotta stop fast. you mean tyres to go along with the 17" you buying ? imo: if you can afford it ? , or if you wanna change the look of your vehicle to go along with the new rims, but didnt you say you didnt wanna alter your car due to the warranty as well , not too sure if they pick on this though, but it may seem that it will, and thats all i can answer for you, in my own personal opinions, hope this helped :] -jeffy edit: hrmm, i was wrong it was the british/french who made the the imperial units, majorilly british, :P