Hiya, OK I have the following tyres on my bike at the minute (came with them on so don;t blame me! 90/90/21 and 130/80/17. I picked up a Pirelli MT90 Scoprion A/T 90/90/21 for the front and want get the matching rear tyre. However, the Haynes Manual recommends 130/80/17 but the Pirelli site recommends the 120/90/17 as does the Mynetmoto site? Any thoughts?