These days one of the most popular modification trend is using larger diameter alloys for old vehicles (sometimes for new vehicles also). This is mostly done to get a modern modern look for the car. Of course it gives a nice shape for some old cars but sadly not for all the cars!Most people prefer larger diameter wheel than what their cars had originally. But they pay the price later since usually cars are made to use some specified sizes of wheels which have decided by the manufacturer after lot of tests. The major problem experienced by the owner just after they put new wheels is that wheel hiring the the mud guards or wheel arches while the car bumps and when they are steer the front wheels. If the above problem is too worse they not gonna use those wheels longer. For our case, lets assume that we do not have the above problem.
So! the car goes fine now. Now let's talk about the secondary problems. Since the wheels are larger, they hit the ground more. So the friction between tires and ground increases, this leads us to many problems. Bigger weight is put on engine, gearbox, transmission system,steering system, breaks and literary every mechanical part of the car because whole car is on its wheels.
This means that the wastage of above parts increases. It is sure that you car will start to drink more fuel and your wallet will loss its weight faster! Your loving car may get into more troubles even which have not discussed here.
Therefore the conclusion is simple, you must really think several times before putting new set of wheels to your car. Most of the time it is between "Beautiful car+ Wasting money" and "originality car+ Saving money". It is always better to go to a qualified professional mechanic or an engineer before you change your wheels.