VOKSWAGEN Mk4 Golf GTi - Rub a dub

Q
I recently bought a Mk4 Golf GTi 1.8T on a 'T' Plate (1999) as a project car, it is already lowered and has a set of 18in RS4 style rims on it, but when I replaced the clutch I noticed there are signs of the wheels fouling the inner arches. The wheels are a bit knackered and the lowering looks like a bodge job, so I will be renewing the suspension also, but for now I wanted to know what wheel offset you would recommend to prevent wheel rub in the future as I am looking to buy some new rims.
The rims I have seen have an offset of 5x100 and are 18x8, I will be running 225/40r18 tyres and will be lowering the car a total of 30mm from standard.
In your opinion would this offset be ok or would I need some spacers fitting?
Thanks in advance for any help you may be able to offer!

A
You've provided the PCD (Pitch Circle Diameter), width and diameter, but no ET. Wheel offset is always calculated via a measurement called ET (Einpress Tiefe) or pressed in depth, so we've no idea what offset you plan on running. Anyway, 8x18in wheels should be fine on a Mk4 chassis so long as it hasn't been lowered more than 40mm and is running the correct VW approved offset of ET38. It's not uncommon for people to run 8.5 (f) and 9.5in (r) wheels with offsets as low as 9.5in, but to achieve this requires arch modifications. Your set up should be fine so long as you opt for smaller diameter coilovers to prevent suspension clearance issues. If you lower the car more than 40mm you'll need new anti-roll bar drop links to prevent the driveshafts rubbing when the suspension is under full compression - although you can have the chassis legs C-notched if you plan on going crazy with the lowering and know a welder you really trust! Also consider fitting 205/40x18in stretched rubber to pull the sidewalls a little further and aid arch clearance, if the problem persists get your arches rolled by a company local to you who sell aftermarket wheels and tyres.