Yep

Can be seen pretty clearly on the ZII tirerack image: http://www.tirerack.com/tires/BigPic...wall=Blackwall

Luckily most tire manufacturers seem to be pretty consistent with where they place it on the sidewall, but using this as an indicator only works in consistent conditions.

For me it tends to be more of a "tires feel sloppy", up the pressure and "I have no grip" lower the pressure game rather than purely a numbers game. Always trying to find that perfect compromise between the two depending on the conditions.

I wonder if there is such a thing as a valve stem that bleeds itself when reaching a certain pressure? Kind of goes against what I just mentioned and is probably not a good idea with how much pressure fluctuation there can be, but does have me wondering.

 

The arrows show where the tread ends. You aren't going to have grip riding on the sidewalls. So the arrows are a good indicator of where you dont want to go past. Like I said, use the arrows as a roll over indicator, then you're close. That will just get you close to where you want to be. I find on my direzza z1's I get too much rollover in the mid 30's, so I usually run in the upper 30's and find thats where I get best grip as well. As stated earlier, conditions can change things so you need to experiment. But its a good starting point to get you close to where you want to be. I also found I needed to have the fronts a bit higher than the rears.