Originally Posted by
robow
Though knowing your tire pressure may not be welcomed by all, for those who feel they can obtain an accurate reading by simply squeezing the tire, you're a far better man than I. When I've played the game of squeeze, guess the psi, then take a reading, I almost always guess much higher than it actually is.
I'd be the first to admit that at best I could say the pressure is "at least" some value and never be able to exactly say what the pressure was or if it was over a little. How well I could gauge would depend on the tire size, the desired pressure and how supple the tire is. The stiff not so supple sidewall on something like a Marathon Plus makes it harder to judge than on a tire with a thin supple sidewall.
When riding every day, if I pump my MTB tires to 30 psi front and 35 psi back and give them a squeeze every morning I notice how much each is dropping in pressure pretty well if my arthritis is in check. I rhink the daily checking of the same tires is part of what keep one calibrated enough to notice the difference. Checking tem once a month of checking some other tire would be less accurate. These days it flares up too much and too often to rely much on a pinch test though.
As long as my arthritis isn't too bad on a given day I can tell well enough whether it will be a problem when I get to the rooted singletrack where the rim will bottom out if the pressure is much lower than optimum. I can't say how many pounds low it is with much accuracy though.
On tour with some tire/pump combos it is easy to get the right pressure by how much effort it is to pump the tires. That isn't always the case, but sometimes it is. If you know for example that all your pump can manage is the exact pressure you need a guage becomes kind of moot. Sometimes it might be possible to feel the level of effort to get a given pressure if you know the pump well. Kind of like how many mechanics know what many specific torques feel like without a torque wrench. On the other hand some pumps are really easy to get pressures greater than you need and others may be inconsistent.