The lower profile front and smaller rear tyre makes all the difference, about 1 inch. You see, Size does matter
Oh aye. I didn't think about that. I had a 748 a few years ago and I could just about manage it with my short legs. I think I remember once sitting on a 996 and it did feel a bit taller. But thinking about it a bit more....the specs for both bikes were seat height 790mm, surely this would be measured with specified tyre profiles?
In Falloons book both are shown as the same but, as you have found, they are different. Maybe it is the angle of the seat due to the lower profile front tyre. You can't reduce the tyre profile and keep the same height.
As from the factory but, I think most 748/916/996/998 riders use the 120/70 front - 180/55 rear combination as it's generally considered the best setup...
