I have both the 349's and 406's. I want to try them on my Merc too. The early runs had some issues in sizing for the 349 size. I haven't heard of any issues in the 406 and the 349's have been fixed. I have the Sun CR18 rims for my Swift and there were no issues there. I have the Brompton Green tires on my Merc which are a very fast tire anyway according to GS's testing and my experience bears that out.