Dunno about Pirelli's on the GS but why bother ? The tourance is generally acknowldged to be the best for mileage, dry grip, wet grip and after sales , in case you have a problem.....Bloody hell I sound like an advert ! ....so why go messing with others ? I can understand wanting to experiment with off/on road combinations but out and out sprts tyre on a big trailie in my mind will mean just spending more on tyres for no material benefit. I reckon you will be hard pushed to beat the tourance as a package deal but if you want a set for the track and another for commuting and another for off road then your possibilities are endless