John I keep my tyres to spec as often as I can. I run 2.9 bar on the rear as the manual states.
I do a lot of twisty/sweeper type riding and for most of the rally I was fully loaded (panniers and topbox) and for the last 800klms was also 2up.
We covered the best piece of road I have ever ridden on the second to last day that may be the cause of the wear.
In North Queensland, just outside of Cairns we descended what is called the "Gillies Ranges" which was 19 klm or 12 miles of back to back twisties that apparently holds 258 bends/corners while it descends about 2500 feet.
The vast majority are speed rated at 40kph with the rest at 30kph. The surface was fresh and clean, I was in heaven.
After the first 20 or so corners I had the GT scraping something on the left hand side everytime and this was while loaded and 2up.
So I might be the cause of this unusual wear.
I did find an entry on another sports bike site when I googled it that showed the same problem with another rider though.
He had run what looked like a white paint roller over a section of the tread that clearly showed the cupping in the tread.
Oh well, at $275 fitted and 8000ks already travelled on it I figure Im down $100 if I replace it now and if thats the cost of that riding experience I got out cheap.
Unfortunately no 180/55/ZR17s available in Australia for at least another 3 weeks??