I am a bit retarded when it comes to thinking about offset and tire diameter for wheels, so I need some advice please.

I found these rims online and I thought I would buy them and try a different look for a while.

http://nashville.craigslist.org/pts/2850982528.html

I know that the car would lower A LOT due to the smaller wheel/tire size, but is the offset okay? It's an 18 offset. Thanks

They'll change your speedo readings too... IMO they are too small but the offset is too far off also... Mini has a 42 offset.

Yeah that's what I was thinking but I just wanted to be sure. It's a shame, I thought the Mini would look pretty retro with these.

Look at the ones on my MCS, in my gallery.
They were $360 shipped, off eBay.
Not bad and you've got to be careful what you're buying but there are some deals to be had on 4x100 rims... Some retro looking ones too.

These would fit the original Mini, I don't think these will clear the brake system. If I remember correctly the rotors are 10-11" and then you have about 3-4" for the calipers. I'm not in front of mine so this is purely from memory.

You can add spacers in to help with the offset and, in this particular case, you would need a 5mm spacer. This would also provide you 43mm more space inside the wheel well to the strut housing.

If you measure everything correctly and it clears the brakes, get the 5mm spacer, and have the spedo/odo retuned for the new diameter, then you are good.