Patronising I may be but excuse me if I don't want to share the road with someone who for the sake of a few £££ thinks they can second guess the manufacturer and fit either a completely different size or a different load rating to that originally fitted. 99.9% of the time there'll be no issue but the one time when you're on the limit and your decision to save the £££ lets you down I'd rather not be faced with 1.5t of out of control 159/Brera/Spider.
You my friend obviously live in blind faith that the manufacturers choose this size of tyre because any other size would compromise the handling and safety of the car .......NONSENCE
During a car's lifespan many critical components will be replaced by non originals items..e.g. brake pads, exhausts, clutches, TYRES, bulbs, oil .....etc.
If you honestly believe that fitting 245's insted of 235's will have any effect on safety, even on the extreme limits, then you obviously don't understand anything about tyres.
My decision to change to a cheaper tyre isn't purely based on saving a few quid. I have 4 cars at the moment including a Ferrari so I commit a fair portion of my earnings to upkeeping my cars and I never compromise when it comes to safety.
Martin G hit the spot when he said that Alfa choose a unique tyre size which will only be made by premium brand manufacturers in order to get some sort of financial kick back into their pockets
If you look at the 3 sizes of tyre's (17's 18's & 19's) that these cars come from the factory fitted with. They're all different in width, profile and diameter so how anyone can be so nieve as to think that only one size/width/profile of tyre can safely be put on this car is beyond belief ........wake up and smell the coffee !!