Tyre size help

[Cruz]

I have the chance of getting some second hand 18" rs6 replica alloys for my avant however the only thing that is putting me off is the fact they are fitted with 225/45's and not 225/40's as i think they shoulld be.

Would they still fit ok ?

Btw my car has been lowered by 30mm

Thanks in advance cruz

 

[Oranoco]

I think depending on rim width 235/40/18 is the best size. Saying that I run with ss2/40/18's purely as a cost issue as the rubber is over £100 a corner

 

[AndyMac]

225/40/18 is the correct size (0.8% bigger rolling radius than stock, 235 is 2.1% bigger).
225/45 is 4.4% larger than stock so way over the 2.5% recommended.
They are over an inch bigger in diameter so clearance could be an issue, but more importantly they will effect the gearing and speedo.