View Full Version : Tire Gauges - Which is the most accurate

12-18-2008, 02:56 AM
If you don't feel like reading, Accutire was the most accurate gauge. One place you can buy them is on Amazon for $15.99 (http://www.amazon.com/Accutire-MS-4751WC-Digital-Programmable-Gauge/dp/B000RN4GT6/ref=pd_bbs_sr_5?ie=UTF8&s=automotive&qid=1229590177&sr=8-5) plus shipping.


Analog dial gauges were 2nd. The common pen gauge was the worst off showing as much as 7 lbs lower (showing 28psi) when a tire was in reality at 35 psi. The pen gauges also got worse when tire pressure was lower.

The long version:
Original posting Here (http://townhall-talk.edmunds.com/direct/view/.ef017dc/0)

Part 1 of 3
Everyone talks about tire pressure but just how accurate are those gauges you use to measure tire pressure. I started out with a collection of 38 tire gauges (loaned to me)
Various sizes and shapes, some new and some very old. Also we tested some digital
gauges some cheap the others expensive. Our test was conducted at our aircraft maintenance shop and against a highly accurate calibrated air pressure standard. I took each gauge and measured three air pressures consisting of 25, 35 and 45 lbs.
All the testing is done and the results in Parts will be published at various times.
Part one consisted of the most popular tire gauge called the pocket or pen type gauge which cost anywhere from $ 1.00 to $ 2.50 range and they have a white plastic dial reading. I tested 5 new ones (Victor, Monkey Grip etc) that were purchased at nationwide chain and auto stores. Each of the new ones read entirely different pressures with the worst being as much as 6 lbs. lower at 25 lbs. While an exact duplicate gauge read 3lbs. lower at 25 lbs. The new ones where mostly 3 lbs lower at 25lbs but improved at the higher pressures of 35 and 45 lbs. There averages where about 2 lbs. at the higher pressures. I tried exercising the dial a few times by pulling it in and out and taking the readings again and some improved by as much as a lb. at the lower reading. I then test older gauges of this type 3 to 10 years and the results were worse in some cases. It seams the older the gauge the lower the accuracy and they are the worst at the lower pressure. Some were off as much as 8 lbs. By the way all of the gauges we tested read low except one and that had an obvious defect. I took the older gauges and sprayed the dial with WD-40 and exercised it about 10 times and then I went back and redid the test and improved the readings to that of a new gauge. One gauge was 7 lbs lower at 35lbs and after my operation the gauge improved to about 2.5 lbs lower. One gauge that was 10 years old had better accuracy than one that was 3 years old, but generally the older the gauge, the lower the accuracy of gauges of this type. You get what you pay for.
In conclusion. If you want 30 lbs put in the air till your pen type gauge reads 28 lbs. and don't forget to exercise the dial a few times before checking the tire pressure. On the older ones spray the dial with WD-40 or some silicone lube and exercise the dial about 10 times. The average after we got them working was about 2 lbs. low Part 2 deals with more expensive gauges with some surprising results until then-by

Part 2 of 3
Tire Gauge Accuracy In Part 1, we did an evaluation of the cheaper pocket or pen type gauges. Part 2 consist of the more expensive heavy-duty double-headed type of gauge. Price range is in the $5.50 to $13.00 range. Basically the same names as indicated in Part 1 and a few new ones like ACCU. Most were purchased at local retail and automotive stores such as Napa ,Advance etc. We also tested some Analog or dial type of a gauge. Since these gauges cost more, we expected more from them and they didn't disappoint us. Since these gauges have a much larger range than the cheaper pocket type, we had to expand our testing to the 100lb. range. These gauges were tested at 25,35,45, (lower range) 60, 75, and 90 lb. range, which we called the upper range. Some where brand new, some where old like over 10 years. The gauges with the metal type indicators read about 1 to 2lbs long over the short range and about 1 lb. long on the higher range. Long means that for a known source of air pressure 35lbs. these gauges were indicating 36 or 37 lbs. Exercising the indicators did nothing to improve the accuracy. As these gauges start to get old (6 years and above) they tend to get a little sloppy on the higher end indicating as much as 3 to 5 lbs. higher. The shorter range still remained accurate within 2lbs. The newer type replaces the metal indicator with that of a white plastic dial much like the cheaper pen or pocket type. Easier to read I guess. These type of gauges read differently over the ranges, much like the cheaper ones. On the short range these gauges indicated about 1 to 2lbs. short. So for 35lbs. they would indicate 33 to 34 lbs. On the upper range they were very inconsistent with some reading 1 lb. short while others reading 1 to 2 lbs long, while down in the lower range they were all short. Exercising the indicators a few times improved some in the upper range but not in the lower range. Still overall the accuracy over both ranges was very good. The analog or meter type of gauges were very inconsistent but accurate. Some were short while some were long over the ranges and the brand didn't seam to matter. Two identical read differently. The 8 we tested were within 2 lbs in both the lower and upper ranges. Just remember to check to make sure the gauge reads zero before checking air pressure. Most come with an adjusting screw to do this. I dropped one on the floor and it indicated about 3lbs long. When in the first test, it indicated 1lb short over the ranges. After I zeroed the meter, it was ok. One analog type was reading all over the place as much as 8 lbs off. Here the meter had a static charge on the meter face. I rubbed a little Wd-40 on the meter face and it was ok after that.
The results show once again you get what you pay for. These types of meters showed pretty good accuracy over the ranges and age didn't seem to slow them down on the lower range.
Part 3 which consist of Digital Gauges will follow soon. One tested so accurate, I went out and bought one and tested it for repeatability and it indicated the same as the first. Which one was it? Stay tuned Until then---by

Part 3 of 3
The final report deals with the accuracy of Digital Gauges. We only had 8 gauges to test in this series, since most people use the gauges we tested in Parts 1and 2. Some of the brands we tested were Victor, Accutire, Majestic, and MG. Since these gauges had indicators up to 100lbs and more we tested them at 25, 35,45,and 50 lbs., which we called the low range. The high range indication consisted of measurements of 60,70, 85 and 100 lbs. All of the digital gauges tested were very accurate over both ranges. We caution you to read your directions carefully, since some of the gages required a self-calibration prior to using. If you don't calibrate them your reading can be off as much as 5 lbs on the lower ranges. The $6.00 gauges we tested were off only 1.5 lbs on the short range and about 2 lbs on the higher range usually 85 lbs. and up. The more expensive Gauges such as Accutire tested the best. The $14.95 gauge tested 0.5 lbs long on the low range and 1lb. long on the higher range. We tested the Accutire lighted background model $30.00 and it read perfectly in the low and higher ranges. It was off by 0.5 lbs (short) at 100 lbs. Every other pressure I tested it at read the correct pressure. I went out and bought one (Sears) and tested it for repeatability and it tested the same. Overall these gauges were very accurate and some do require a self calibration. They were all very easy to read. In time I feel more people will buy them. This concludes my report and I hope it was helpful.

12-18-2008, 08:44 AM
Nice write up, I know I have been the victim of a bad tire gauge. Air pressure makes such a difference in traction and contact path, I think it ranks in the top as far as setting up your 4x4 for success.

12-19-2008, 07:51 PM
I have been in metrology for over 30 years, have designed pressure measurment instrumentation for medical devices, and have tested many tire pressure gauges I have owned against $5k+ NIST calibrated Drukk and Mensor pressure calibrators. The surprising conclusion I drew was that the el-cheapo pen-type mechanical gauges were as accurate, or more accurate than the fancy digital ones. And their precision was as good, with proper technique.

A possible reason is that it costs a lot more to manufacture a digital gauge than a mechanical one, (parts and labor) so precision and accuracy is sacrificed, dollar for dollar.

I have measured $30 digital gauges off by as much as 6 PSIG @ 30 compared side to side with $2 mechanical gauges. I did this some years ago and expect that transducer technology has likely improved since then. In my experience in designing and manufacturing pressure-measuring instrumentation, the transducer is the largest contributor to error in precision (AKA repeatability), and manufacturing quality control is the largest contributor to error in accuracy (a given reading compared to a better standard, such as NIST, within a given uncertainty).

I respect Edmunds a great deal, and it is probable that transducer precision and manufacturing quality control has improved since I did my own tests. But I respect my el-cheapo pen style guages, both in accuracy and precision. I know, I tested them myself.

FWIW, precision (repeatability) is far more important in tire pressure applications than in many others. If you have an auto locker, like a Lock-Right, you should have better than +/- 1 PSIG difference on the tires on each end of that axle. I found precision better than that in all of the pen-style tire gauges I tested. And in tire pressure applications the accuracy difference of say, 2 PSIG, really makes no difference in the real world. 32 versus 34 PSIG isn't going to make a difference as long as the tires are inflated to the same pressure relative to each other.

Happy cruisin'!

12-19-2008, 10:12 PM
How about the difference in accuracy between a pen style vs a dial gauge? Which have you found has better repeatability of those two?

12-19-2008, 10:33 PM
Anyone have experience with this inflator? Maybe the trigger handle is hidden by the main part of the body? If it's actuated by solenoids I think that would be cool! Totally unnecessary but fun lol. It's supposed to have an accuracy of +/- 1%.
On Amazon for $70 (http://www.amazon.com/gp/product/B000TP0DNA/ref=olp_product_details?ie=UTF8&me=&seller=)


12-19-2008, 10:51 PM
Having used several gauges I have found that repeated pressure tests is best. having used el cheapos and expensive ones I found this best.

I inflated two tires with a dual hose inflation set up that way I know they are of equal pressure. Like Jeff said it does not matter much if they are 34 or 36, but using this technique I can make sure all tires are equal. I can do the same with low pressure, as long as I use the same gauge I am able to inflate or deflate my tires to the pressure" I want.

12-19-2008, 11:10 PM
How about the difference in accuracy between a pen style vs a dial gauge? Which have you found has better repeatability of those two?

I only tested two dial gauges, and they were not as repeatable and the pen style gauges - my recollection was that one was around 2 PSIG and the other was around 1 PSIG, while all 4 of the el-cheapo pen style gauges I tested were +/- better than 1 PSIG. The digital gauges I tested were non-repeatable to 6 PSIG, but they were relatively inexpensive, around $30. It seems likely that you could pay a lot more for better repeatability and accuracy in a digital gauge if you chose to.

I have a dial gauge at the outlet of my compressor, and another one at point of use. They routinely disagree by 2-4 PSIG. I'm used to that, and for their purposes, I don't need high accuracy.

Again it goes to manufacturing costs - a dial type gauge costs more to manufacture without more $ going into the mechanism, and a digital gauge costs more for the battery, transducer and display, none of which contributes to the instrument's overall accuracy.

As I wrote above, with tire pressure measurements, +/- 2 PSIG accuracy is perfectly fine, but you want precision (repeatability) to be way better than that, better than +/- 1 PSIG for our tires, especially with an auto locker.

12-21-2008, 08:45 AM
If you don't feel like reading, Accutire was the most accurate gauge. One place you can buy them is on Amazon for $15.99 (http://www.amazon.com/Accutire-MS-4751WC-Digital-Programmable-Gauge/dp/B000RN4GT6/ref=pd_bbs_sr_5?ie=UTF8&s=automotive&qid=1229590177&sr=8-5) plus shipping. ...
And mine should be here 1/2/09. Thanks, Glen!

Here is a surefire way to make sure your tires are inflated equally. I first thought it would require that you run around to each one real quick when you disconnect them... but no. Duh. BTW, Roger is the minitruck tech guy for Trails.

Pretty durn schlick:

12-21-2008, 07:09 PM
And mine should be here 1/2/09. Thanks, Glen!
Red_Chili, want to compare pressure readings on the Pizza Run?

I just ordered the Steelman inflator (http://www.amazon.com/gp/product/B000TP0DNA/ref=olp_product_details?ie=UTF8&me=&seller=).
We can do our own comparison readings between the Accutire guage and the Steelman inflator. Should be interesting.

12-21-2008, 07:59 PM
You are such a gadget guy!

We have 3 dial gauges and they are real close.

12-21-2008, 08:24 PM
You are such a gadget guy!

We have 3 dial gauges and they are real close.
lol! It's true, I won't even try to deny it. It's downright near a sickness. When I'm old and senile I'm sure my house will look like a tornado hit a Grainger and petered out in my living room.

12-21-2008, 08:46 PM
It is funny how the hi-tech things are to make our life easier and they do seam to complicate it instead.

Your AWESOME digital air gauge is going to have it's batteries die and I'm going to rescue you with my simple dial gauge.

12-21-2008, 08:55 PM
You guys are a bunch of SPOF victims! (Single point of failure). I will continue to carry the dial gauge, and my compressor has a sorta accurate gauge on it that suffices should the two other ones die...

But you are talking to someone who carries spare axles, has two batteries, has two compressors not one, uses an on board welder... THAT is a SICKNESS! :lmao:

Uncle Ben
12-21-2008, 09:35 PM
I wish I could find valve stems like I had three sets of tires ago! Pull the core and they would whistle about 12#....perfect! :rolleyes: If you are using CO2 and are worried about how accurate your tire gauges are you really need a life! All gasses fluctuate with temperature so just because you filled it to 35.276 # after finishing the trail doesn't mean it will still be at 35.276 +/- .001 after 20 miles of road travel! ;) :lmao::lmao:

12-21-2008, 09:41 PM
Of course when your battery dies in the gauge and you have to get home you can always fill your tires and drive the car the old fashioned way, with uneven pressure :eek::hill:

12-21-2008, 09:41 PM
Bill that 2air/4air stuff looks kind of interesting, hadn't seen that before. Also looks like a bunch more stuff to carry around to be honest. But I like equalizing aspect, I bet I could figure out a way to hard plum something similar.. and I carry only one guage, it's an Accugage that I bought when I got a CO2 system years back. Seems close enough..

I do have 3 compressors though... oba + a 12v for each battery :o :bolt:

12-21-2008, 10:12 PM
I have the 2air set up. It is not from him but another company. I got it from somebody on expedition portal for cheap. I like the idea of getting the frt and rr tires the same pressure when wheeling. :o

Like UB said when we are driving home the tires will all be different temps anyway so the pressures will be different unless you are using nitrogen. Just packing our rigs with extra weight effects the pressure. More on one side will cause that tire to heat up more and increase the pressure.

I don't really think a few pounds difference will affect our driving/handling that much. Adding bumpers and big ol tires on the rack causes more problems DAMHIK :rolleyes:

Don't get me wrong I like gadgets as much as the next guy, and I did a bunch of research on air gauges about 6 months ago. Seems the gauge I had was off by 8 pounds so when we were on the snow run I kept sinking in as Red Chili was floating on top. I lowered to 4 pounds or so I thought, actually 12 pounds:o and still no good. After I tried Bill's gauge and saw the difference I adjusted my gauge to read the "correct" poundage.

I will have to compare my set up with the new gauges you guys have, hope I'm not to far of.:D

12-22-2008, 02:16 AM
You guys are a bunch of SPOF victims! (Single point of failure). I will continue to carry the dial gauge, and my compressor has a sorta accurate gauge on it that suffices should the two other ones die...

But you are talking to someone who carries spare axles, has two batteries, has two compressors not one, uses an on board welder... THAT is a SICKNESS! :lmao:
So you're saying that I'm not going to get better only worse? Not only will I be planning the failure points but having instantaneous triplicate redundancy built in? I suppose instead of fighting it I should just accept it. If I'm doomed to a life devoid of normalcy then I should at least be happy in my insanity.

With this new epiphany I've decided I'd rather be ignorant, blissful, and lucky than well informed with a sense of self responsibility. Besides my personality leads me to do what ever it takes to be lazy, no matter how much work it takes. ;)

BTW I'm jazzed to see your rig in motion. The last time I saw it you had the instrument cluster torn apart. IMHO you have one of the sweetest rigs in the nation. Beautiful!

12-22-2008, 02:24 AM
Like UB said when we are driving home the tires will all be different temps anyway so the pressures will be different unless you are using nitrogen. Never heard of nitrogen being immune to temperature. What's being said about nitrogen? Or maybe I misunderstood?

12-22-2008, 08:34 AM
Yes Nitrogen (N) isn't affected by temps as C02 is. Race teams use it and a lot of fleet car/truck companies use it too. I am using it in my GMC, wife's Toyota and filled up three of my friends cars. It has been around in the retail market for a while but really popped up last year when gas prices were sky high and everybody was trying anything to get better MPG. Last year my Argon bottle was empty so I swapped it for a N bottle and split the cost between all of us. So far the same pressure as last year.:thumb:

Now dealerships are advertising it, do all 4 tires for 39.95 :eek: I don't think that is a good deal but some do.

Because Nitrogen is pretty costly it is not a good thing to use in our crawlers unless money doesn't matter. The constant deflating and inflating of our tires would waste a ton of money.:(

Here is a link that explains it better, plus it is a pretty cool site ;)


Uncle Ben
12-22-2008, 08:54 AM

BTW I'm jazzed to see your rig in motion. The last time I saw it you had the instrument cluster torn apart. IMHO you have one of the sweetest rigs in the nation. Beautiful!

Oh pooh.....now you did it. We just finally were able to get Bill's hat to fit his head again and you just went and popped the adjustment band right off.....there will be no living with the man again for months..... :rolleyes: :bawl: :bowdown::bowdown::bowdown::bill:

12-22-2008, 09:19 AM
part of the reason i set up my york was because i was kinda getting tired of the pressures in my tires getting so out of whack after wheeling. did it make a huge difference to switch to air instead of CO2? yeah... could i even notice when my tires were 5psi high or low? no.. not really.

i air down with a cheapo, 99 cent analog dial guage i got from home depot in the checkout isle.. i air up with an ARB super duper dial guage i paid a lot for. They both read right on.

Have I been totally screwed before thinking i knew my tire pressures? you bet your a$$. For about three autocrosses, and two drivers' ed's in a row last year I could not for the life of me figure out what the hell was wrong with the CRX. It just handled like crap. I finally noticed the guage i was using was about 7psi off in most cases, and 10 in some. yikes. now I at least cross check my new guages with another old one before calling it good.

pretty enlightening. I got lazy and used an old guage i had rolling around in the car instead of my nice ones and it bit me. I guess any of them could be off though.

FWIW, my locker acts really funny if the tires aren't within a few PSI on the road... but normally they go up and down together. Off road, it is always locked anyways it seems.... and tire pressures seem like they always end up all over the place.

12-22-2008, 09:55 AM
Back to the issue of Nitrogen. My CO2 setup started as a Nitrogen bottle. (it was leftover from a job, FREE) I couldn't believe how fast the pressure dropped in the bottle. Later I found out that the same size bottle will hold 3 times the CO2 as N. CO2 compresses down and turns into a liquid where N does not. I traded my bottle in for a CO2 bottle for just the cost of a fill. They also converted my regulator for $6. (High Plains Welding)

12-22-2008, 12:18 PM
You are right on, when I got a bottle of N we were only able to fill up 5 cars. Two sets of tires were small, like mini cooper tires. The others were 265/70/17. We were barely able to get the last set done.

The same size C02 would do 20 or so fill ups.

12-22-2008, 07:53 PM
Whenever I read threads about CO2 versus N2 I have to chuckle a little. Yes, they have different molecular weights and have different specific heat, however they both obey the laws of physics: PV=nRT, where P=pressure, n=number of moles of the gas, n is a constant, and T is temperature in Kelvins. They will both change pressure EXACTLY the same with the same change in temperature for our purposes.

There have been claims that Nitrogen is better than plain air with it's oxygen and water, in terms of holding pressure for extended periods of time and degradation of the tire rubber compound, but for our purposes, N2 has no real-world advantage over CO2.

FWIW, when calculating a pressure change in a gas due to temperature change in a fixed volume, you must always use Kelvins for your ratios. To get Kelvins, simply take the temperature in C and add 273 (or 273.15 if you want to split hairs). Thus, if you start out with 30 PSI at 0C (32F) and warm it up to 20C (68F), the warmer tire pressure will be 30 PSI * 293 K / 273 K = 32.2 PSI. Kelvins cancel and you are left with PSI as your units (one of the easy error-checks when formulating equations in physics).

However, and this is REALLY important, there can be HUGE differences in gauge accuracy at different temperatures. This applies to both mechanical gauges and especially to digital ones. If a digital gauge does not have temperature compensation built in (which costs more $$ to build), it will be all over the map at different temperatures. I have designed with pressure transducers which require in excess of 2300 ppm of compensation requirements. Not only that, the Temperature coefficient will vary from one transducer to the next, requiring individual calibration (read=expensive production costs).

01-23-2009, 03:05 AM
Steelman Digital Tire Inflator Review. I wanted to post up with info about this a while ago but have been busy. Anyhow, the short version is I don't recommend it. Looks cool but that's about it.



Front. I like the rubber boot that it came with. Nice and thick.

Back side Easy access to change the two AA batteries.

A closer look at the face. The plus and minus buttons inflate or deflate.

I changed out the black hose with a red flex hose and put a swivel connection on it.

A closer look at the ends

PSI readout

Bar readout

KPA readout

Even though the Steelman has some cool features such as backlighting and an accurage gauge, I ended up shipping it back for a refund. The little things about it, which I'll talk about later, just didn't make it better in my opinion than a regular ole $13 inflator like this one.

The above Rand inflator is the one I've been using for the past year and I really like it. For one it has a dial gauge that faces you when you pull the trigger. The trigger has a long lever making it easy to pull even with high psi. The dial gauge is fast and reliable. I added a swivel connector to mine for the heck of it but I really don't think it needs one.

The Steelman has a couple of things I'd like to see changed before considering it to replace my cheapo. The + inflate and - Deflate buttons are too hard to press especially when running around 225 psi. I didn't like pressing hard on them for a few seconds. I think I'd really dislike it trying to hold it down for 5 minutes.

When I aired down to 15 psi and tried to get a reading from the Steelman the first three attempts showed 3psi. The fourth time it showed an accurate reading but several readings later proved unreliable. It seemed to be either dead on or way off. It didn't have the problem when my tire pressure was up around 30psi.

The Euro style chuck is heavier duty than most except for where it counts. The spring is too weak causing it to lose it's bite into the valve stem threads. Again the Rand did better.

It has an audible beep when you reach the selected pressure or above. It got irritating quickly. If you were able to hold the button and it stopped inflating automatically with an audible this would be nice but it doesn't automatically stop inflating so as you back off to deflate you keep getting the beeping. It's too bad the buttons were not solenoid controlled for an easy touch and automatic stop.

The backlit display can be turned off to conserve battery power but the default mode is on. So every time you use it you have to shut off the display if you don't want to waste the batteries in the daylight.

So while it looks really cool and has a good idea behind it the performance just doesn't hold up for real world use. Kind of a bummer I really wanted to like it.

01-23-2009, 08:11 AM
BTW, Glen, thanks very much for your kind words.

No worries, UB, God seems to have on His project plan a step-by-step rollout of a series of events designed to preserve my hat size.

FWIW, that darn cool pressure gauge is only as good as the batteries. On the snow run, I had discovered at its first attempted use that my center console - full of junk - depressed the button sufficiently to drain the battery despite the auto off feature.

Back to mechanical.

01-23-2009, 09:34 AM
i've found the best guages to be the 2.99 specials you buy at walmart. i've found the worse were any guages you bought at harbor freight.

01-23-2009, 09:56 AM
Interesting, since they come from the same place. :lmao: