Re: Euro Wheels and Handling (Bora20)
It's surely not going to improve handling overall, but it won't hurt it very much.
1. Yes, most 'euro' styled setups have smaller overall diameter wheels due to lower profile tires as well as stretched tires, lessening diameter. This does two good things: shortens your gearing thus improving acceleration, and also, it means your car has a lower center of gravity while not overtaxing the suspension geometry.
2. It's also good in that the lower offset wheels increase track width. Wheel width doesn't matter at all - what matters is offset, and how wide the tires are. usually the tires are not much wider than stock but with the lower offset, it puts them farther outwards.
But the bad..
1. Stretched tires don't grip as well as non-stretched tires, because the tread is no longer evenly weighted - the outside and inside edges will have more pressure on them than the middle, so the efficiency of the contact patch is lessened.
2. Wheel bearings won't have the same lifespan due to the added pressure put on them by lower offsets. I don't consider rubbing to be a performance attribute, but you might need to limit suspension travel to the point that it doesnt handle well in imperfect conditions to stop the rubbing.
Those are the facts.. in the end, its not going to improve much, but those who think it kills performance are also just as wrong.