I've just bought a set of 18x7.5 wheels off ebay and am wondering what size tyres I can get on them.
They are 4x100 ET45 and only weigh 8kg each!
I have 3 sets of wobblies and some 20mm spacers which are on the car already with my Rota's.

Can I get away with 225/40/18 or will that give clearance issues?

5kgs!?

What are they?

Sorry Trappy. That was a typo.
They are 8kg each and are KEI Flight wheels.

225/40 18 will be too tall - you'll need 225/35

If you want to see how much bigger 225/40 is, pop round to mine and have a look at my Alfa GT - it runs this size

Too tall as in won't fit or too tall as in wrong ratio?
Ideally wanted to stay bigger than 35 profile if possible.

you should be alright with 225/40 but they may rub on full lock and your speedo will be out too .

I don't mind the full lock issue too much and the speedo will only be about 2mph out at 60 so not so bad.
As long as I don't have rubbing against arches etc and will fill the arches a bit better too.

they shouldnt rub the arches

Thanks nismo.