So how much importance should be given to profile when selecting a tyre? I'm not talking about the aspect ratio or width. I mean the shape of the tyre (in profile - yes, I know they're round from side-on!). On my last bike, which was relative stable steering-wise, I went from a rounded profile, wider rear to a slightly narrower, more v-shaped profile. The change, front and rear, made quite a lot of difference in turn-in characteristics (much quicker). Now, I have a very quick steering bike and the current Pirellis on it are more rounded than, less v-shaped. I need to replace the rear, but I would like to try something different. The question I have is that if I go for more v-shaped rear will it make the bike less stable, and also will there be issues in matching with the existing partly-worn front? Do I need to keep to the same family of tyres (Diablos) or can I mix them? Don't need to worry much about wear right now.