Help! New Alloys

[Corolla_XLI]

I will be purchasing a new set of alloys for my E10 in a couple of weeks time. The thing is, I can't decide whether to buy 15s or 17s :D . The car will look nice on 17s when it's lowered. I am also wondering what style of wheels will suit the corolla the best. I.e. multispoke, 7 spoke, 5 spoke, chrome plated etc...

The thing is I want to have my car scarping the ground , that's why I'm considering shelling out for some 15s, plus they would not scrape the arches if the car is fully loaded.

If I buy the wheels with 195/45/15s tyres and lower it 40mm, the car will be sitting 55mm lower, since the 45 profile tyre is 31mm less than my original tyre in diameter(15.5mm lower when the wheel is put on).

I just wanted to ask whether this really low profile tyre will affect my speedo readout, as places like tyresave say the max difference in tyre diameter should be 2.5% and this is 4.7%.

Cheers.