Analog is best for interpreting rates and values i.e. acceleration on speedos and tachs and such. But tire pressure, unless you are trying to measure a ginormous leak-down rate, is a static value. I trust my keychain accuracy implicitly; it hasn't given any reason not to.
I do have a larger digital gauge too; the only benefit it has over the keychain is accuracy displayed to the tenths while the keychain only shows whole numbers. Tenths don't mean diddly to me though.
Of all the people who promotes a simple way of living, I'm surprised you have a fancy digital tire gauge. You're like an Amishman with a Tempo Calm down, I'm just bustin' your chops Pops.
The reason for the analogue perspective is this: e.g. you have a tire that's severely underinflated. With the analog gauge, you can see via hash marks that "I need 20 more lbs." With a digital, you have a number and have to do some Math. I dunno -- maybe it's just me -- I tend to be a visual processor of information, and it's easier to calculate how much time that pump needs to be attached to the valve stem.
Ryland - those old pen-style testers were good back in the day, but became "cheap" over the years. If you can find one from the 50's and 60's, then you actually have an instrument. The Digital guages are, for the most, accurate. I got my old one free from the TireRack when I ordered a set of tires. I used it during Autocrossing and it seemed to be right on the mark to show the increase in tire pressure as the heat of tire rose.
Most of the time I get really doggone close by counting one pound per second ie. if the tire has 20 and I want 40 I'll count to 20 while filling.
I knew Dracula before he could count !
1 pound per second...for how big a tire? Large volume tires fill slower (from the same source), tiny tires fill NOW!
Ah! The gauge knows! It's easier to "bleed down" than to refill & refill! I'm just pulling your chain....
Around here we have Sheetz gas stations that have of all things free air machines. They are the kind that you dial the PSI that you want and it rings as it pumps and when it stops ringing you are at the set PSI. Of the 4 Sheetz that I have stopped at and filled air (I always check my air when I am there) the closest to real PSI was 10 off. One I had to set the dial at 80 PSI to get to 50. So I always only trust my gage.
Seeing that I can see how many people are driving around with 1/2 flat tires if they trust those things.
Public air hoses suck! As does anything else the public (ab)uses! Your own pressure gauge is essential! Digital? Who need the tenth pound read-out? Did you ever try to read this half pound difference in low-light conditions? ARGH! 21st century clutter! NASCAR is partially responsible for this hair-splitting ( at least the commentators [common 'taters?] are...)"...adding a half pound to the right front!" ...while the car's in the pits. BS!
People drive around on low tires because they don't check 'em! Ever! Ask anyone you know "When was the last time you checked your tire pressure?" You'll get a blank look! "Me"? I rest my case...
...and besides that, I've heard of tires blowing out due to under-inflation, but almost never for over.
So what exactly would happen if we ran 80 psi in our tires? (I know it's a dumb question, but I need a mental picture).
They will blow, trust me, done it, seen it. Kind of a strange question for someone titled as a Senior Vehicle Analyst?
It is risky enough to excede the car mfgr's suggested pressure (especially in rear motored cars, not much of a problem today) due to ill handling, but don't bump much above the tire maker's for sure. Anyhow, the max tire pressure is for max load rating too, a lot of older cars, especially European wagons, would have empty and loaded ratings posted for inflation.
And for blowing out for underinflation, I have seen and done it....front right Vredestein on a Toyota at speed....the tire picked up a nail and developed a slow leak that I did not notice, I could see indications of the tire riding on the sidewall for a period of time, it happened on a long trip.
I just rememberd a nifty gauge that a friend picked up from the bicycle shop, you screwed it on to your valve stem, then filled it thru a valve on the gauge body, so you could watch the presure rise, without having another object in your hand.
How long will a digital presure gauge stay acurite? I meen, what do they have in them that reads the presure, and how long will it last?
They have a pressure transducer and should stay accurate forever - they also recalibrate when you turn them on so the 0 reading is nice. They are great for detecting a slow leak because of their resolution - one tire down 0.2psi in a day means maybe 1 psi in 5 days! I even detected a difference in pressure in the right rear because of tire heating by the muffler. They are also good for low pressure tires on ATVs and for that low car tire to see that it had 10.2psi in it. Finally they are great to calibrate your other analog gauges.