Everything else is inflated, I guess tires ought to be too. Firestone is now advertising about keeping the proper pressure in the tires. I’ve always used my own gauge when filling my tires up, as I’ve heard the gas stations’ pumps are not too reliable. So, I really don’t know how they work. I guess they make that ticking sound until the air pressure that it is set at is reached. But then do they just don’t supply any more air? Or do they do so silently?
My front tires take 35 psi. I set the pump today at 35, and my tire had 32. But I could not get any more air into the tire. The other tires filled OK. My guess is that no more air was being supplied as I had reached the set point according to the pump, butnot according to my gauge. And the pump wouldn’t give out any more air. Is that right?
While it is true you should always use your own gauge, note that the little handheld wand gauges are not overly accurate as well. They can often stick, and have a low level of accuracy. Even still, they are good enough for filling tires.
You should be able to hear the air flow into the tire, even at a very low pressure differential.
Why not just set your pump at 38, and see if it gives you 35?
By all means, get your own tire gauge. The wand-type gauges are worse than useless - they have cheap little internal gaskets which can leak, and this can lead you to overfilling your tires. Go to an auto parts store and find a gauge with a metal housing and a dial - you should be able to get one for less than $10. IMHO, the new digital gauges are not a good choice - I got one for my mom, and the batteries only lasted a few months - and they are not designed for easy replacement (which means that I broke the ABS plastic housing when trying to disassemble it).
By the way, when you said that
you were assuming that the filling station equipment was working right. You can always overfill a bit, then bleed a little out until it’s correct (that’s what the little nipple on the back of the gauge is for - use it to depress the valve stem). You don’t need to worry about the tire bursting until you get way over 50 psi (assuming that your tire isn’t damaged and was mounted properly). And finally, be advised that tire pressures should be measured cold - if the nearest filling station is more than a mile away, you might want to look for a small compressor so you can take care of the job in your own driveway.