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Do you trust your tire pressure gauge????

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  • Do you trust your tire pressure gauge????

    Up early this morning to see my granddaughter off to a college related flight to Japan. Only to get notice the flight is delayed. So, I checked the forum and noticed Bob Palma mention misplacing his tire pressure gauge.

    That got me to thinking about the half-dozen I have lying around. However, for some time now, I've been wondering about them, and how accurate they are. I have two digital, and several traditional gauges. They are about as common as pencils. You see them in all shapes, sizes, pressure ranges, prices, and "give away" promotional advertisements. While many/most seem to be the traditional "plunger" style, there are some using an actual circular analog air gauge. Some "lock" the pressure for reading convenience, with a button release. The latest, is the digital readout.

    Of all the ones I have, I have selected only one to trust. I took them to my local tire shop, and compared to the one the "Pro's" (?) use. The one that matched the tire shop gauges, is kept near my air compressor. It is marked with a piece of camo duct tape. Even after doing this, I don't have full confidence it is correct. With several gauges, the readings among all are slightly different. When you watch any type of auto racing...even a half pound of air is critical. Then, we know the goofy political crap of a few years ago, where we were told correctly airing up our tires would help save the world along with buying squiggly little light bulbs.

    Seriously, air pressure is critical. For our cars, and especially, for those of us with motorcycles. I believe we have discussed this before, but some discussions are worth repetition. Therefore...this thread. What steps have you taken to ensure you have a good gauge? How much thought do you give to the accuracy of your tire gauge? What would you recommend?
    John Clary
    Greer, SC

    SDC member since 1975

  • #2
    John, you make a good point. I, too, have several pressure gauges and have wondered about their accuracy. Unlike you, however, I do not possess the gumption to test them! I know that they give variant readings. I tend to use the analog dial model simply because it's easier to read.
    We have a convenience store near the house that provides free air. It has a digital readout. Those give the APPEARANCE of accuracy, but it's just a display: no more or less accurate, so who's to say? Plus, that particular machine has seen better days. It struggles to pump past 26 psi. Guess I get what I pay for!
    Mike Davis
    Regional Manager, North Carolina
    1964 Champ 8E7-122 "Stuey"


    • #3
      I have a tenth reading digital gauge that I had tested here at work a few years back. It was .1 off back then. And no I haven't had it checked since shortly after I bought it. I have an analogue gauge also that's close to the digital, but with a 1-1/2" dial...pretty difficult to read with much accuracy.

      I've thought about buying a more expensive "race" quality gauge...but so far...haven't.

      To answer John's question, yes, because of the design, I do trust the digital gauge I'm currently using.
      On the other hand, "repeatability" is as much, if not more critical than accuracy.



      • #4
        Funny you should bring this up, as just last week an emergency situational need for a gauge that read over 100 psi presented itself and my "good" heavy duty truck style gauge has disappeared. I live 3 miles from work and I have another similar gauge at home, so I made the 10 minute round trip and all was well. I knew I'd never see that gauge again, so I procured another from the local NAPA store we deal with. On the packaging it claims to be accurate to 1/2 pound at 120 pounds, and accurate enough to set other gauges to it. So we will see as time goes by, as the gauge I trust is an analog dial that has proven itself to be accurate enough against the pro's gauges, and has been trusty on a repeatable basis. I do keep the pencil style gauges in all my vehicles for on the road use as they get me in the ballpark. When I am on the road, in my little "emergency" box that goes with us, I keep a can of tire glue (fresh) and tire plugs and the tools to use them. Also have a mini air compressor. Yes, I've had to use the stuff a couple times, and it is a lifesaver. Bill


        • #5
          how about the quality control of the tires and their ability to hold stated air pressures ??


          • #6
            Originally posted by jackb View Post
            how about the quality control of the tires and their ability to hold stated air pressures ??
            Hmmmm. The last tire failure (other than punctures from road debris) I had was in 1960 and it was a cheapo recap.

            I used to buy "best quality" tires, usually Michelin. Then, when my daughters Toyota needed four new tires, I went to Western Auto and bought two Michelins @ $60/ea, and two cheapo store brand at $15/ea. None ever failed, and the cheapos were still good when the Michelins were worn out.

            So I think it's hard to buy bad tires. I always buy whatever is cheapest. So far, so good.

            But to answer the original question, no I don't know whether my tire gauge is accurate, but it does agree with the gauge on my air compressor.


            • #7
              I have ONE gauge I trust and have had it for 30+ years. I bought it from a reputable quality vendor and it is "steel".

              I also have a handful of "cheapies" that I keep at least one in each car. I figure that even the cheap one will get me close. I always test those against my "good" one. I have yet to check it against one that is deemed "professional". Repeatability for any of them can sometimes be questionable, depending on physical position of the gauge, how hard you press it onto the stem, and how much I had to eat before bending over to check tire pressures. Where is the "official, certified" tire gauge testing station?

              I cannot determine what brand my "good" one is. If I could, I would buy another one, knowing that what I buy today is NOT what I could have purchased 30 years ago.

              I have always wondered: Where do all the stray tire gauges go? You never see them laying around, or out on the roadway, or in your pencil drawer...... As many as are sold, you would think they would be littering the roadways with their chrome cylinders of defiance.........
              Dis-Use on a Car is Worse Than Mis-Use...
              1959 Studebaker Lark VIII 2DHTP


              • #8
                Originally posted by BILT4ME View Post
                ...I have always wondered: Where do all the stray tire gauges go?...
                If you ever find that "other sock" will probably be full of those "spare" tire gauges.
                John Clary
                Greer, SC

                SDC member since 1975


                • #9
                  Tire gauges for aircraft are tested for accuracy once a year. Don't get caught using an uncertified one.

                  I have compared the five or six gauges that I have and there is over 3 pounds difference in their readings. Which one do I trust? I just won't pay to have them tested. Where can you test them?


                  • #10
                    I am not a racer, so allow for a 2-4 pound variance in tires and gauges. I do not even bother to add air ii a tire, if only a couple pounds low. I use gauges that only go to 50 PSI, since the wider the range, the more likely to be further off, and more difficult to read.

                    I keep gauges in each car, in tool boxes, etc., so have several. To validate accuracy, I cross check several of them at a time, by compare readings on the same tire. If one varies to far from the rest, say 3-4 pounds, it gets tossed. The military calls this, "cross calibration", and recognizes it as a field expedient for most TMDE (testing, measuring, diagnostic equipment).

                    I like the KISS principle, and believe one source of anxiety is the tendency to spend too much time worrying about things that do not need to be worried about, much.
                    Last edited by JoeHall; 06-24-2016, 08:53 AM.


                    • #11
                      Since I started filling my tires with Nitrogen, I have seen very little loss over time and virtually no fluctuations from hot to cold temperatures. It costs a little more up front, but my experience has been nothing but positive with Nitrogen. As far as trusting a tire gauge, for the most part they are accurate enough for daily drivers. My father was a drag racer and he had much better gauges and had them calibrated regularly for the pit tools, but had an old cheapy for his regular car. 2-3 psi is normal deviance for a tire pressure gauge.
                      "The bitterness of poor quality remains long after the sweetness of low price is forgotten." -B Franklin


                      • #12
                        I have several pencil-type gauge for the cars, another higher reading one for the 2R15, a dial gauge and an electronic gauge. They all read within a couple of pounds of each other but I favor the electronic one. I'm with Joe in that I'm not going to sweat a couple pounds of air pressure. Speaking of nitrogen, the Durango I bought new in January came with nitrogen filled tires. This being my first experience with nitrogen, I watched the tire pressure closely using the dashboard display. (How accurate are those?) In April, we drove it from Arizona to Durango, CO for a few days and ran into cold temperatures and a couple snow storms. In the cold mornings the tire pressure was down to 26 lbs (normal was 36 lbs in AZ temps). It did come up to 36 after many miles of highway driving. Is this normal for nitrogen? Running that low did worry me.
                        Kingman, AZ


                        • #13
                          I certainly don't entirely trust the cheap gauges. I had a nice gold colored pencil type that came in its own leather case. I checked it a few weeks ago and found that it was reading WAY low so I threw it out. About two weeks ago my wife called and said the tire pressure monitor light was on, what should she do? I told her to measure the tire with the pencil gauge I always carried in the car. I told her if it wasn't too low, just drive the on home and I'd check it. She called a little later to tell me that neither our grandson or her could find the gauge in the car. Then I remembered, that was the one I threw away. So, I told her to go to a convenience store that had an air machine and make sure all were at 33 psi. She was very close to the Weis grocery store gas station and they did have a machine (and it was free). She put the hose on every tire and had them all reading 33 per the machine. When she got home I checked the tires first with a decent pencil gauge then a digital gauge. They both agreed on the readings, One tire was at 48, one at 46, one at 38 and one at 36. So, don't trust an air machine either. Any how, a couple days later the monitor light came on when I was driving. I still hadn't replaced the gauge so I decided to stop in the first convenience store about a mile away and pump up the leaking tire. Talk about sticker shock. The air machine at that store required $1.50 before it would help me. And, the nozzle leaked air like crazy. At least I got the rest of the way home and pumped up the tire with my compressor then called a tire shop I could trust. They told me they weren't busy and bring it on it. They found a nail right in the center of the tread and they had to dismount the tire to patch it- $25 total.
                          In checking my gauges my heavy truck-type gauge (which was in the truck) agreed closely to the pencil and to the digital. However, I have an air attachment on my compressor hose that clamps on the valve stem and has a round analog gauge that gives you the tire pressure in the tire and lets you watch the increase in pressure as you add air. It always reads four pounds higher than the other gauges so I also adjust for that when I use it.
                          My son the mechanic has the ultimate gauge- an electronic, termperature compensating Snap_on gauge that he probably paid $100 for (why he can never get out of debt to Snap-On). I would probably trust that one.
                          Paul Johnson, Wild and Wonderful West Virginia.
                          '64 Daytona Wagonaire, '64 Avanti R-1, Museum R-4 engine, '72 Gravely Model 430 with Onan engine


                          • #14
                            Since air is about 80% nitrogen, the thermal expansion rate for air and nitrogen would be about the same. Likewise, the loss rate of air through the sidewalls would be about the same. I have tires on the front of my backhoe that run at 55 psi, and I add air about once a year, sometimes less. I always use the tire bead sealer and my tires tend to hold air very well. I can think of no reason to use nitrogen in vehicle tires unless they are trying to avoid corrosion problems that you might get from the moisture in some air compressors.

                            Years ago, I think in the 80s, one of the aircraft brake manufacturers had a tire explosion when testing brakes on one of their big dynos. A lot of testing was done and it was discovered that the inner liner of the tire was gassing off a combustible gas at extreme high temperatures. The tire inflation pressure on some commercial jets run as high as 200 psi, or slightly more. The burst pressure of the tires is about 500 psi or higher. With the size of these big tires, a burst at that pressure is like a sizeable bomb. But a combustion explosion is much worse. The wheels are made with fuse plugs that are intended to melt before the tire pressure becomes high enough to create burst pressure, but there have been a few instances when they did not.

                            Considering all these factors, the decision was made to require that tires on large commercial aircraft be serviced with dry nitrogen. The manuals will allow some refills with air, but not to exceed 50%, so that the oxygen level remains at no more than 10% (i,e., air being 20% oxygen.) Unfortunately the manuals in some cases did not explain why this was important, and an airplane was lost because of this.

                            As for tire gauges, I bought one of these and I highly recommend it:

                            Last edited by 48skyliner; 06-24-2016, 11:15 AM.
                            Trying to build a 48 Studebaker for the 21st century.
                            See more of my projects at


                            • #15
                              Originally posted by sasquatch View Post
                              In the cold mornings the tire pressure was down to 26 lbs (normal was 36 lbs in AZ temps). It did come up to 36 after many miles of highway driving. Is this normal for nitrogen? Running that low did worry me.
                              It's a gas so it will obey the ideal gas law. PV=nRT Warmer - higher / Colder - Lower