I don't think there's room to lower the forks in the triple clamps because of how the handlebars basically bolt on over the top of them. Plus, a 180/55 is probably going to be very close to the same height as the 190/50 so it's not going to raise or lower the rear much or affect the speedo much. Most people are talking about a 190/50 vs a 190/55. The 190/55 IS taller than the stock tire. So I'm sure raising the rear is part of the handling difference. However, the tire also has a "sharper" profile which makes it fall into corners quicker. And the affect on the speedo is a positive one because it corrects for almost all of the factory speedo error and makes it more accurate.