[Zunige]

Your GTV was originally fitted with 14 x 5.5 wheels. Upgrading to 14 x 6 wheels is common. Essentially a 14 x 6 wheel with a 185/70 tire is a stock configuration. The biggest issue with that size is that the better tires are simply not available in a 185/70 size. (At least not in the U.S.A., and I do realize that you are in NZ.) That said, tires made today are simply much better that those made 25+ years ago, so this comparison is relative to what would be considered most desirable. On the 14 x 6 rim, you can fit a 195 tire, or even a 205 tire. With the 195 you may or may not be able to tell that maneuvering in a parking lot feels a tad heavier. With a 205 tire on the 14 in. rim, you will be able to feel the difference when parking, but not anything that would really make you regret the upgrade. (Most people adjust to this very quickly and it isn’t an issue.) With both wider tires (and better tire choices) fitted to a stock weight wheel, you will be able to tell that you have a “grippier” set-up, and you will notice a handling improvement.

If you go with the 15 in. lighter wheels, and the size choices you are describing, you will notice an even greater improvement in handling. The lighter 15 in. wheels and wider tires are a very nice set-up, in my opinion. A 185 mm tire on a 15 x 6 in. wheel seems narrow to be me. Alfas that came with an OEM 15 in. wheel had a 195 mm tire as stock. The only drawback with going from a 14 in. to a 15 in. wheel, on a car with a stock suspension, is that the ride will be a little stiffer. Much depends on your particular level of comfort. The choices that you are describing however, are all well within a street spec, so it’s hard to see how you could go wrong even with the most “extreme” of your choices: 15 in. wheel with 195 mm wide tire.

Best regards,