Originally Posted by
nhluhr
The chart is absolutely wrong. It has no accounting for the vast difference in tread and sidewall stiffness between various tires. Compare for instance the Conti Gator Hardshell to the Conti Supersonic. One of them will damn near hold you up without any air in it.
One of the best pieces of advice about product design and manufacturing I ever got, was some 40 years ago, bt it applies here.
"Never sacrifice good, on the altar of perfection".
This article and the related charts are a good starting place, but are not intended to replace experience based fine tuning. There are any number of variables that aren't included, including wall stiffness, wall shape (tire width/rim width) tread compound, and rider speed. If we hold out for some perfect scientific formula, we'll have nothing we can use as a starting place now. To their credit the authors were among the first to open a discussion of pressure, weight and cross section, so while it's not perfect, the information makes a good starting place for thinking about tire performance.
For example, rebound and traction loss are related to speed, and a pressure that seems to offer low rolling resistance and good traction at low to medium speed, may cause excessively skittish handling and loss of cornering traction on high speed descents.
Years ago we didn't use science or formulas, but were attuned to the issues and trade offs and found things like optimal tire pressure through experience. I as taught to increase pressure 5psi at a time, and riding under various conditions, until handling suffered, then dropping back to where it was OK. I still use a similar method, and as I described earlier seek balance between good ability to climb on bad pavement, and low rolling resistance.
Even after years of riding the same equipment, I'll still make an adjustment based on anticipated conditions.