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Old 12-18-2008, 02:56 AM
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Default Tire Gauges - Which is the most accurate

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 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

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
DCH

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
DCH


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.
DCH
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Last edited by Glen; 12-18-2008 at 10:41 AM.
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Old 12-18-2008, 08:44 AM
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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.
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Old 12-19-2008, 07:51 PM
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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'!
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Old 12-19-2008, 10:12 PM
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How about the difference in accuracy between a pen style vs a dial gauge? Which have you found has better repeatability of those two?
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2001 4Runner SR5 Auto - Armorology Front Bumper, Warn M8000, 1/2" Technora line, - Toytec coilovers - OME 851s w/Bilsteins - Yokohama Geolandar MT+ 305/70R16 - F&R ARB lockers - Stubbs HD-SKO Sliders - Engel 15 Freezer - Low profile cargo - Laptop mount - Thule roof basket - Viper 5900 remote start - Cobra 8WSXTII CB Radio - Stainless 304 rear bumper and tire carrier w/chainsaw mount.
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Old 12-19-2008, 10:33 PM
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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

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2001 4Runner SR5 Auto - Armorology Front Bumper, Warn M8000, 1/2" Technora line, - Toytec coilovers - OME 851s w/Bilsteins - Yokohama Geolandar MT+ 305/70R16 - F&R ARB lockers - Stubbs HD-SKO Sliders - Engel 15 Freezer - Low profile cargo - Laptop mount - Thule roof basket - Viper 5900 remote start - Cobra 8WSXTII CB Radio - Stainless 304 rear bumper and tire carrier w/chainsaw mount.
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Old 12-19-2008, 10:51 PM
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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.
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Old 12-19-2008, 11:10 PM
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Quote:
Originally Posted by Glen View Post
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.
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Old 12-21-2008, 08:45 AM
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Quote:
Originally Posted by Glen View Post
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 plus shipping. ...
DCH
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.
http://4crawler.com/4x4/ForSale/4air.shtml

Pretty durn schlick:
http://www.4x4wire.com/reviews/2air/
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Old 12-21-2008, 07:09 PM
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Quote:
Originally Posted by Red_Chili View Post
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.

We can do our own comparison readings between the Accutire guage and the Steelman inflator. Should be interesting.
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2001 4Runner SR5 Auto - Armorology Front Bumper, Warn M8000, 1/2" Technora line, - Toytec coilovers - OME 851s w/Bilsteins - Yokohama Geolandar MT+ 305/70R16 - F&R ARB lockers - Stubbs HD-SKO Sliders - Engel 15 Freezer - Low profile cargo - Laptop mount - Thule roof basket - Viper 5900 remote start - Cobra 8WSXTII CB Radio - Stainless 304 rear bumper and tire carrier w/chainsaw mount.
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Old 12-21-2008, 07:59 PM
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Glen
You are such a gadget guy!

We have 3 dial gauges and they are real close.
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