Why won’t a gas station compressor overpressure a tire? Surely it can build pressure beyond most tire ratings, yet there is some kind of governor to prevent this (usually a dial lets you set your target). How does this work? There must be some kind of adjustable pressure regulator in the machine, but what is it? An adjustable-size flow orifice (as opposed to a fixed orifice) perhaps?
Any Dopers know the SD on how this works?
I have never seen a gas station air compressor that had a separate pressure regulator for the air lines on the pump islands. The tire chuck has fairly small passages in it, so the flow rate is restricted compared to what the pipe is capable of delivering.
The air at the pump islands was capable of delivering the same 90-125 PSI we had in the shop.
Of course now we have lots of gas stations that don’t have shops or big compressors. There is a rectangular box somewhere that you put quarters in to get air. These have a small tankless compressor that will only produce so much pressure. I have never tested on of these for max pressure.
I know of one design that had a dial one sets to the desired pressure, but I admit, not many have this do they?
Those used to be quite popular, but I haven’t seen one in decades.
I’ve seen them around here a bit. You set the pressure you want, attach the hose end to the tyre and wait till it stops. It makes a clicking noise as it goes, this gets slower, once it stops clicking the desired pressure has been reached.
It would be a fairly simple arrangement I guess. The pump already has a pressure gauge, all it needs is a feedback mechanism to shut off the air once it attains a certain pressure.
They can and will overpressure your passenger car tires.
Check out the inflation PSI for a full-sized heavy-duty pickup running proper light truck tires. Sometimes you’ll see numbers above 80 PSI.
On edit:
Heck, my mountain bike used to spec 65 PSI for over-the-road operation, with 45 PSI specced for technical trail riding.