I'm a total newb at this, so would like to be tought how to work out sizes I need in plain English lol.

What would I need for a tyre to be 215/45/17?

 

A 210.625 17
Won't be a million miles of.

Slicks! Eh what for?

 

What are you planning to do on slicks mate

 

http://www.cargister.com/calculator-race-tires.SJ.

 

Thanks dudes, cheers sj that's a great calculator.
To put on my wheels joe

 

Obviously, what are you using the car for to need slicks is what I meant?

I thought you were going wide arch? 215 is narrow for a slick tyre

 

Lol, widearch is the very last on list, (was jogging my brain before on what wheels I can get in my size requirments and for me to do some jdm research).

Nothing really, just it's good to know what's suitable and if I see a used set going cheap on eBay etc then I'll get some for trackdays etc.

 

Right oki doki, slicks may not be the best for track days. Could even cause you problems. There's no such thing as cheap slicks dude, all these you see on eBay ex btcc etc are crap. Yeah they are not good.
Would you consider a set of 888's or similar?
There's a good chance you will get something like that under your standard arches

 

I'm talking Tarmac slicks here, ideal for trackdays so not sure what you mean?
Likes of dmak, Avon, Dunlop etc, seen some selling for upto £200 for a used set which will do loads of trackdays, ive seen a few folk run slicks on trackdays and tbh they flipping fly round the corners like crazy.