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Tire Pressure Gauge Readings

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Jul 12, 2015, 12:41 AM

Post #1 of 9 (3102 views)
Tire Pressure Gauge Readings Sign In

Hi. I'm trying to put an accurate amount of air in my tires. Here's my dilemma. I repeatedly tried EIGHT gauges. I had a long pencil gauge read 22, and a round gauge read 32. We can toss those gauges out. That leaves 6. I had 3 gauges read 29, coincidentally all of the round dial variety. The other 3 gauges read 27...2 mini pencil gauges, and the pencil gauge attached to the free air compressor at the gas station. So my dilemma is...which 3 gauges are accurate, and which 3 are 2 pounds off? Quite frustrating, indeed. While we're at it, does anyone know of a dependably accurate gauge on the market? Thanks so much...

Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 12, 2015, 3:40 AM

Post #2 of 9 (3087 views)
Re: Tire Pressure Gauge Readings Sign In

Love this question and IMO totally valid. Wish I could give you a one brand answer for what to trust for accuracy but an attempt would be ones I've purchased in blister packs at NAPA have been the closest so far but for a long time now.

Yup - those ones for a buck at the counter are frequently WAY off and it does matter. So, what I've done and still room for error is when my compressor (two screw in gauges on the thing) cuts off and fill a portable air can till they are equal - my portable can with gauge too has a tire valve like fill port also and check it while at what compressor said then mark that pencil type or other gauge as "OK" with a Sharpie marker. Probably going to put a date on it now as well.

After so much use or abuse being dropped, checking air with a tire full of "Flat Fix, Slime, Calcium Chloride (used for weight on some tires) or other) have to wonder what it does to the dang things.

It's going to matter that you get a nice spit free reading on tire valve and I do each twice on larger tires that should read the same. Keep in mind low volume things, bike tires, air shocks can be such low volume that just checking lets some air out vs larger items.

When you get ONE known good one mark it as your best and probably don' use that one except for testing other gauges! Valid point and many are dangerously off. Own tons, one or more in each vehicle and assorted types. I just bet the screw in ones are closest and use those as the standard.

This is another buyer beware thing. Same crap with antifreeze testers BTW also!
When time for new ones I'll buy several and mark bad ones BAD and take those back hoping they wont be resold!



Jul 12, 2015, 8:15 AM

Post #3 of 9 (3078 views)
Re: Tire Pressure Gauge Readings Sign In

Thanks for the reply, Tom. Very nice of you to help the auto store determine which of their anti-freeze testers are bad. In a perfect world, someone in the supply chain would have already done that.

Yes, I'm in the process now of trying to determine which 3 of my 6 gauges are correct. I would have been inclined to think that the 3 round dial gauges, which were much more expensive, would be the accurate 3. But the 2 cheap pencil gauges match the pencil gauge on the free air compressor at the gas station, so my search is still on.

I have never purchased a screw-on type gauge, so I guess the next one that I purchase will be that type. I suppose in the meantime I can try going to one of those auto parts stores that have free checks for things. Maybe they can check my pressure with a couple different gauges that they deem to be accurate. I will give that a try.

Thanks for your valuable input!

(This post was edited by joezapp on Jul 12, 2015, 11:16 AM)

Hammer Time
Ultimate Carjunky / Moderator
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Jul 12, 2015, 8:41 AM

Post #4 of 9 (3077 views)
Re: Tire Pressure Gauge Readings Sign In

Inexpensive gauges are rarely accurate at all. You'll even be lucky to get the same gauge to give you the same reading twice in a row. I've gone through this for years and the only way I resolved it is a bought an $80 digital gauge that reads in 1/2 pound increments.

The one thing you want to make sure of when you do this is you always check them before the car has been driven and with approximately the same ambient temp. Pressure readings will vary dramatically with temp changes and the only reliable time to check is before the vehicle has been driven that day and when it's parked out of the sun.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

(This post was edited by Hammer Time on Jul 12, 2015, 8:42 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 12, 2015, 9:42 AM

Post #5 of 9 (3073 views)
Re: Tire Pressure Gauge Readings Sign In

This stuff w inaccuracy is totally irritating. It does matter more than ever. Some to many vehicles use exacting pressures front or rears - the spare and so on. I also deal with WET filled 2/3rds so they make gauges just for that if you like parting with $10 for pencil gauge.
Sorry to sound ticked but am. Antifreeze! OMG - you have to know that. Thank you PRESTONE by name brand (tester) you suk! bought several knowing they'd not all agree and didn't. Measured exact 50/50 and want to see exactly -34 not 10F off either way or lots more off.

Arggh! Price should buy you quality and accuracy but isn't necessarily the sure bet. I default to many agreeing one after the other with the same conditions.
What most folks don't know and add it to your trivia to win a Coke at a bar.

How many pounds/PSI does plain air go up per ea. 10 degrees Fahrenheit of temperature? A. ONE - PSI for each 10F up or down. You notice this most when first cold snap comes thru the dash tires pressure warning go nuts. Tires about all say check when cold and that's why as well.

I'm ticked as this is expected to be a DIY thing and they do that to the stuff! Arrrrrrrrrrr!



Jul 12, 2015, 11:33 AM

Post #6 of 9 (3065 views)
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Yes Tom, agreed. And that first sudden cold snap is when it's most important. But it's also important on a hot summer day before a long drive, as you don't want to overfill due to an inaccurate reading and then have a blowout.

Hammer Time, excellent advice for those who don't know indeed. Check the pressure on undriven tires that are out of the sun.

I hate the thought of having to spend $80 on an accurate gauge, but we'll also pay in the long run with tires not reaching their full life expectancy with bad readings, so I may just have to invest in one like yours. The digital aspect is nice also, although I'm certainly not convinced that digital necessarily means accurate. Quality will still matter I'm sure. And it may just take an $80 investment to get that.

Ultimate Carjunky / Moderator
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Jul 12, 2015, 11:45 AM

Post #7 of 9 (3064 views)
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I'd venture to say a digital tire pressure gauge is going to be the most accurate as long as it is calibrated correctly. Does your vehicle have TPMS and displays tire pressures?

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Jul 12, 2015, 11:48 AM

Post #8 of 9 (3062 views)
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Hi. Thanks for the reply. Unfortunately, my car does not, but I would have to agree that a properly calibrated digital gauge would be ideal.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 12, 2015, 2:09 PM

Post #9 of 9 (3057 views)
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Beat on this once more: Digital isn't always the answer as things that require a battery have a habit of failing just when you need it and don't have another - luck. Just in and don't do car stuff much anymore but sooooo flipping hot took a shot at an A/C check and charge up on a stored Benzo. Air over pavement was 140F (digital thermo) and a digital scale I left in the sun dammit went all nuts being too hot that yet another new battery solved.

IDK - someone gave me a digital tire gauge in a fake leather case. It suks. Takes 3 tries (that exact one) to get any reading as the tip is lousy and spits air out while trying. Can't win.

First test on A/C was a home-made gauge by me to read static pressure with a tire gauge (just hours ago now) such that with an unknown system that might have been full of goo for all I know would only wreck a tire gauge. It read 5 PSI, is empty for A/C just for that info how to proceed with said, an unknown system. Didn't want to wreck VERY costly A/C stuff on one reading.

Back to the topic. YOU are supposed to know it's hot for a tire that it's on and or in the sun as a factor. If driven a lot tires warm up on their own and or pick up road temps. You still want to believe what you buy is telling what you want and asked for a brand and I can't name one that always right the first time, did mention NAPA as they sell them untouched in a package so at least they haven't be played with by anyone or probably sustain being dropped in the package? No clue who makes them whatsoever - not marked,

Have a great day - Tom

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