Re: definitive 17's info please
Hello, the correct offset (ET) for the GTV and Spider is 30.5, this is also stamped on the inside of the alloys if you purchase original Alfa (Speedline) alloys. The width on original 17" alloys is 7.5", so you should fit 225/45/ZR17 tyres. If you go with original alloys there are two main types:
1) The five hole teledials,as seen on the GTV cup and also used on other 3.0 V6 cars (and 2.0 TS/JTS as well).
2) The highly desirable 5-spoke 'Enzo' alloys, made for the Series 3 cars with the 3.2 V6 engine (can be fitted to 2.0 engines as well).
3) Way back earlier for the Series 1 cars Zender also made optional alloys for the GTV/Spider, the split 5-spoke version looked very good but this was a 7" wheel so took 215/45/ZR17 tyres. Not available now, very rarely come up on ebay.
I'm sure there may be others, just can't think of them at the moment! Hope that helps.