# Inaccurate Tire Pressure Gauge Readings



## MiWolverine (Jun 15, 2009)

I have different readings from 3 separate tire pressure gauges. 2 Accu-Gage and my floor pump. I pumped up my tires (27.5 x 2.8") to 20psi (according to my floor pump) and took readings from the other 2 gauges. One (0-30psi Accu-Gage) reads 14psi, and the other Accu-Gauge (0-60psi) reads 17psi.

I have no idea which gauge is correct. I am compelled to believe that my cheap floor pump has the accurate reading. I bought the Accu-Gages because they came highly recommended. Can these be recalibrated somehow? If not, does anyone have a recommendation for one that is actually accurate? Though, it would be my luck that I would get the inaccurate gauge.


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## slomtbr (Oct 9, 2010)

Consistency is more important than accuracy. Stick to one gauge and find its pressure reading that suits your needs.


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## MiWolverine (Jun 15, 2009)

slomtbr said:


> Consistency is more important than accuracy. Stick to one gauge and find its pressure reading that suits your needs.


While I agree with this, the problem is choosing the most accurate gauge of the 3. I think I will just use my floor pump. The other two are consistent, but I feel they aren't the most accurate.


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## 127.0.0.1 (Nov 19, 2013)

accu-gauge is wicked accurate BUT simply dropping one can send it out of whack
it has a small brass arm that can be adjusted [or which can get bent from abuse]

I had one shipped that was abused in shipping and it arrived all screwed up
----
bottom line is...digital is probably 'most likely' to be accurate

stick with one gauge, get used to it's readings and how your ride goes, then it doesn't
matter if the gauge is exactly accurate... as long as the readings are repeatable it will let you set tires to your prefs


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## MiWolverine (Jun 15, 2009)

127.0.0.1 said:


> accu-gauge is wicked accurate BUT simply dropping one can send it out of whack
> it has a small brass arm that can be adjusted [or which can get bent from abuse]
> 
> I had one shipped that was abused in shipping and it arrived all screwed up
> ...


The most inaccurate gauge (0-30psi) is brand new. It may have gotten messed up during shipping, though.


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## RonSonic (Jan 8, 2005)

Accu-Gage is lifetime warranted. If those don't agree and the error is greater than the spec sheet allows then send one back. Or both with a note saying one of them is off. 

I had to ship mine back once and it was quick and painless.


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## MiWolverine (Jun 15, 2009)

I contacted the seller of the 30psi one I recently purchased and they are sending out a new one. I know they have a lifetime warranty, but the cost of sending it in and paying for return shipping equals the cost of a new one. Though, it would be properly calibrated.


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## MikeDee (Nov 17, 2004)

slomtbr said:


> Consistency is more important than accuracy. Stick to one gauge and find its pressure reading that suits your needs.


Yes, precision is what you want, not accuracy. Pressures are rather arbitrary anyway and should be arrived at through trial and error or experimentation (think suspension air pressure and tire pressure). That's why I use the same pump for my suspension pressure even though I have a couple.


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## MiWolverine (Jun 15, 2009)

MikeDee said:


> Yes, precision is what you want, not accuracy. Pressures are rather arbitrary anyway and should be arrived at through trial and error or experimentation (think suspension air pressure and tire pressure). That's why I use the same pump for my suspension pressure even though I have a couple.


I acknowledged this above. However, I would still like to KNOW for sure what pressure I am truly running.

I received the replacement gauge and it was just as bad as the first. I inflated the tires to 20psi, according to my floor pump, and the gauges read 13-14psi. The tires feel quite firm when squeezing them, like a tire that is inflated to 20psi. So, what I am going to do is send one off to have it calibrated and go from there.


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## alexbn921 (Mar 31, 2009)

If you absolutely must know the PSI in your tires then you need to pay for a good a gauge. Consistency is far more important than actual pressure. I have one of these as my master gauge that all others are tested against. 
Longacre Magnum Tire Pressure Gauge 52001


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## MiWolverine (Jun 15, 2009)

alexbn921 said:


> If you absolutely must know the PSI in your tires then you need to pay for a good a gauge. Consistency is far more important than actual pressure. I have one of these as my master gauge that all others are tested against.
> Longacre Magnum Tire Pressure Gauge 52001


lol, I thought I was getting a good gauge in the Meiser. It came highly recommended by many. However, I am not desperate enough to shell out $80 for a gauge.


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## alexbn921 (Mar 31, 2009)

MiWolverine said:


> lol, I thought I was getting a good gauge in the Meiser. It came highly recommended by many. However, I am not desperate enough to shell out $80 for a gauge.


I'm sure the gauge you bought will be consistent. Sucks that it is messed up. I bought my gauge when I was racing AutoX and 1 psi was the difference between winning and loosing. Have had it for 15 years and will probably have it for another 15+.


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## MSU Alum (Aug 8, 2009)

I bought several digital gauges for the (adult) kids. They all read the same. I've seen a lot of variance in floor pumps and find it very hard to believe that is the most accurate of your gauges.
But slomtbr is right. Determine a pressure that works for you and use the same gauge all the time to reproduce that pressure.


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## MiWolverine (Jun 15, 2009)

MSU Alum said:


> I bought several digital gauges for the (adult) kids. They all read the same. I've seen a lot of variance in floor pumps and find it very hard to believe that is the most accurate of your gauges.
> But slomtbr is right. Determine a pressure that works for you and use the same gauge all the time to reproduce that pressure.


As do I. However, based on the firmness of the tires at various pressures, I am inclined to believe the floor pump over the other gauges. At 14psi , according to the accu-gages, a tire should have a spongy feel to it when squeezed, yet the tires were quite firm. This leads to my assumption that the accu-gages are incorrect. I'm not saying my floor pump is spot on, but I am going to go by that gauge over the others.


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## Harold (Dec 23, 2003)

MiWolverine said:


> As do I. However, based on the firmness of the tires at various pressures, I am inclined to believe the floor pump over the other gauges. At 14psi , according to the accu-gages, a tire should have a spongy feel to it when squeezed, yet the tires were quite firm. This leads to my assumption that the accu-gages are incorrect. I'm not saying my floor pump is spot on, but I am going to go by that gauge over the others.


What makes you think the tire should feel spongy? That's an awful technical term with a lot of calibration behind it, eh?

Your pressure range is right in the middle (sweet spot) of the 0-30 psi meiser. I'd be most inclined to believe that one is most accurate. Besides, as the volume of a tire increases, the way that pressure feels in the hand changes. So a lower pressure feels firmer. On my 26x3.8 tires, 20psi is pretty much rock hard. 15psi is still super firm. 10psi is getting around "hardpack" pressure. I usually ride about 8psi or so for chunky stuff, but there's still enough firmness there to avoid rim strikes. Of course, change tire casings and what you thought about pressures on the previous tires will change. You have to reset your expectations. A firmer casing will require yet lower pressure. A more flexible/supple casing will require higher pressure to achieve the same feel.

So, we come to this. Get your tires at a pressure that FEELS right for where you ride and the way you like to ride. Measure with whichever gauge you want. Then use that gauge all the time to get a repeatable result. At less than 20psi, no floor pump I have is any good. The resolution is insufficient to get within 5psi of desired. Less than 10psi doesn't even move either pump's needle. That's why I have a Meiser gauge. I can reasonably adjust to 0.5psi increments, which makes a difference on high volume tires.


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## MiWolverine (Jun 15, 2009)

Harold said:


> What makes you think the tire should feel spongy? That's an awful technical term with a lot of calibration behind it, eh?
> 
> Your pressure range is right in the middle (sweet spot) of the 0-30 psi meiser. I'd be most inclined to believe that one is most accurate. Besides, as the volume of a tire increases, the way that pressure feels in the hand changes. So a lower pressure feels firmer. On my 26x3.8 tires, 20psi is pretty much rock hard. 15psi is still super firm. 10psi is getting around "hardpack" pressure. I usually ride about 8psi or so for chunky stuff, but there's still enough firmness there to avoid rim strikes. Of course, change tire casings and what you thought about pressures on the previous tires will change. You have to reset your expectations. A firmer casing will require yet lower pressure. A more flexible/supple casing will require higher pressure to achieve the same feel.
> 
> So, we come to this. Get your tires at a pressure that FEELS right for where you ride and the way you like to ride. Measure with whichever gauge you want. Then use that gauge all the time to get a repeatable result. At less than 20psi, no floor pump I have is any good. The resolution is insufficient to get within 5psi of desired. Less than 10psi doesn't even move either pump's needle. That's why I have a Meiser gauge. I can reasonably adjust to 0.5psi increments, which makes a difference on high volume tires.


Here's what I have according to my floor pump: 18 rear, 16 front on 27.5 x 2.8 Nobby Nics and they have a some squish (like that technical term?) to them when squeezed. Now, if I went by the accu-gage, it reads 12 rear and 10 front. Nope, no way in hell that is right. At that pressure, under my fat ass, I would be hitting rim quite often. Soooooooooooo, I'll go with what my cheap, purchased from Chainlove (miss that website), many years old, floor pump reads. That is, until I get something I know is correct, or send the accu-gage in to be calibrated.


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## Harold (Dec 23, 2003)

MiWolverine said:


> Here's what I have according to my floor pump: 18 rear, 16 front on 27.5 x 2.8 Nobby Nics and they have a some squish (like that technical term?) to them when squeezed. Now, if I went by the accu-gage, it reads 12 rear and 10 front. Nope, no way in hell that is right. At that pressure, under my fat ass, I would be hitting rim quite often. Soooooooooooo, I'll go with what my cheap, purchased from Chainlove (miss that website), many years old, floor pump reads. That is, until I get something I know is correct, or send the accu-gage in to be calibrated.


Does it matter which one is "right"?
Pics of your gauges? Which has the better resolution?


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## Brodino (Sep 15, 2008)

MiWolverine said:


> Here's what I have according to my floor pump: 18 rear, 16 front on 27.5 x 2.8 Nobby Nics and they have a some squish (like that technical term?) to them when squeezed. Now, if I went by the accu-gage, it reads 12 rear and 10 front. Nope, no way in hell that is right. At that pressure, under my fat ass, I would be hitting rim quite often. Soooooooooooo, I'll go with what my cheap, purchased from Chainlove (miss that website), many years old, floor pump reads. That is, until I get something I know is correct, or send the accu-gage in to be calibrated.


I agree. Your floor pump is probably closer to accurate. Sometimes I will use my floor pump to top off my motorbike tires and when I go to adjust them using my digital gauge, it is within 2lbs. I have had that pump for years.


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## MiWolverine (Jun 15, 2009)

Harold said:


> Does it matter which one is "right"?
> Pics of your gauges? Which has the better resolution?


Really, it would only be for reference. Though, it would be nice to have a gauge that is accurate. I mean, that is their primary purpose, right? It sucks to still have to guess even after purchasing a device that is designed to take the guesswork out of it. Kind of like a torque wrench. Imagine if all torque wrenches were off roughly 30%. There would be some pretty crappily assembled items throughout the world.


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## 127.0.0.1 (Nov 19, 2013)

MiWolverine said:


> lol, I thought I was getting a good gauge in the Meiser. It came highly recommended by many. However, I am not desperate enough to shell out $80 for a gauge.


it is a good gauge, but it ain't designed for Amazon warehouse handling and Ace Ventura shipping. it's fragile bendy brass bits inside.


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## wschruba (Apr 13, 2012)

Look, whether or not you want to believe it, floor pumps (of the usual 0-120/50 variety) just aren't accurate in the ranges you are concerned with. It is customary to not trust a gauge in the upper/lower 10%, even if the accuracy is +/-1% (hence the reason most floor pumps read higher than 120 psi, the average pressure for a 700x23mm tire). As far as mechanical tire gauges go, the Meiser is about as good as they get before you start buying gas purged/fluid filled hardware.

You, however, are discovering something about calibration: when given a range of pressures you are looking for, choose the narrowest measuring device, not the widest...the chances of it being wrong are much lower. _Technically_, a 0-150nm torque wrench will read out at 5nm, but the reality is very different. It is definitely not strange to get different readings from a 0-150, 0-60, and 0-30PSI gauges.


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## 127.0.0.1 (Nov 19, 2013)

the only tire pressure gauge I really need


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## customfab (Jun 8, 2008)

MiWolverine said:


> Here's what I have according to my floor pump: 18 rear, 16 front on 27.5 x 2.8 Nobby Nics and they have a some squish (like that technical term?) to them when squeezed. Now, if I went by the accu-gage, it reads 12 rear and 10 front. Nope, no way in hell that is right. At that pressure, under my fat ass, I would be hitting rim quite often. Soooooooooooo, I'll go with what my cheap, purchased from Chainlove (miss that website), many years old, floor pump reads. That is, until I get something I know is correct, or send the accu-gage in to be calibrated.


Everybody is trying to tell you that the number is just that, a number. Every time I've switched pumps I wind up adjusting my pressure to the pump. It's also worth noting that the accuracy of the gauge is relative to it's range. So while they may all be +/-2%, that range is a lot bigger on a gauge that tops out at 200 psi than it is on a gauge that only goes to 30. If you want an absolute number then you need a certified gauge, they are expensive and fragile.

https://www.mcmaster.com/#4026k29/=1brmjij

If a $150 gauge isn't in your budget, just go ride your bike nobody is going to think less of you.


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