[W124] Tyres on 17"

[Frank Smyth]

One more question now that I see that my tyres are well worn :-)

I have 17" rims, with 225x45 on the rear and 215x40 on the front - previous owner must have like the "jacked up rear" '70s look. However on Irish roads, those 40-profile tyres are way too harsh. What would be the tallest profile possible with 17" rims ? Not too concerned with messing up the speedometer reading, more concerned with fouling the arches etc.
 
Anyone have 17"s ?