I think ZR is a generic term for high speed rated tyres, however there is still another pure speed rating after it, see:

http://www.carbibles.com/tyre_bible.html

The Avon ZZR which I think may be OE on Aero's now is a Y rated tyre as are the Pirelli's on my S1. The 888's in 225/40/18 size are only W rated which is lower than the std tyres.

This may be an issue for homologating the import to Portugal (Cereals point earlier)... I need to check...

Phil Egginton
1979 4/4 4 seater