I've long said (basically ever since identifying the "breakpoint" in my first Crr vs pressure VE runs)..." 'Tis far better to err on the side of too little pressure than too much." ;-)

As far as a calculator of some sort goes...I used to think having something like that would be cool...but now, I'm not so sure. After all, there's way too many variables to get a true "optimized pressure", or even a range...at which point you're back at using the generalized guidelines as a starting point and going from there with experimentation.

For road or mixed surface use, I'd start with the Berto curves (based on measured tire widths and wheel loads) and go from there.

Edit: IME, the Berto calcs cause the front tire to be significantly under inflated. After all, the load on the front tire increases quite a bit from the static load during braking and cornering.

I usually figure out the rear load, and then drop the front pressure by 5-10% based on the bike setup.

---

http://bikeblather.blogspot.com/