On most street vehicles, a pound or two in either direction doesn't matter but consistency L/R on each axle is always important.

I have a Joe's pyrometer for tire temps, and it was one of the tools that told us something was up with my fancy longacre gage. And the pyrometer double checked with the tire guys stuff.

I have an Accutire bourdon tube dial gauge that I dropped. After that it read 2 psi when the pressure was 0. I opened it up and saw that the linkage between the bourdon tube and the dial needle appeared to be designed to be adjusted by bending a link. I adjusted it to read 0 at 0 and "calibrated" it by comparing it to a couple of other gauges. All were in agreement within about 1 psi. (Edited from previous post.)

https://www.consumerreports.org/cro/tire-pressure-gauges/buying-guide/index.htm

Typo - it was supposed to read 1 psi.

Ah. Rubbin's racin'. And racin' guys spend I would hope more than $70 on a tire gauge. It seems to me if you're going for tenths of a pound, then you are limiting yourself right off the bat to digital pressure gauges that have been tested. I mean it would seem logical to not reach for the old school free O'Reily's stick tire gauge and then be disappointed/ shocked.

Just tested 3 of mine. I was not pleased with the results, but like many here have said, a man with more than one is never sure....

Maybe I should buy another, so I can become confused?

I hope that if you've got 3 or more, that you have a majority that agree, ie, 2:1 or something like that. Then you at least stand a better chance of the 2 being right or closer to right.

Nope, hence my disappointment, and 2 of the instruments are fairly expensive so I was expecting that they would be within a small percentage.



http://forums.pelicanparts.com/uploa...1561233907.jpg

Hence my issues with inflate-gate. They used an uncalibrated car type electric pump in a heated bathroom.

To reiterate,-
I was quite shocked and surprised as my old stand-by which was over 30 bucks back in the day and the other five gauges could find no agreement.
None.
It may, in fact, be right..but compared to what when I get the new gauge?
Will I now have seven gauges that have dysentery derivative dysfunctional psychopathic skill set?
(sort of like those that came up here from the bowls to add their two cents of drool)
There seems to be just no way of calibrating without a 5000.00 dollar machine.
Something so simple sometimes just is not.

If I could find three or four that read close to the same perhaps they would be right...but that is just betting on an average and not a sure thing.

True. That's usually good enough for me, but then I've apparently been lucky enough to get several that seemed pretty close.

Yeah, it certainly doesn't seem like an easy thing to fix if you want to get something calibrated.

Did you change your avatar? It seems different to me.

I think the sun makes very, very little difference. Most of the heat in the tires comes from the deformation of the tire as it rolls down the road. Assuming you're going in a straight line on a good road with a relatively symmetric load side to side on the tires, they'll gain pressure pretty equally.

Gauge accuracy is usually 2-3% of full scale. A 100psi gauge would have 2-3 psi of error.

This was fun for me in my previous life. I invented a oilfield completion system that opened based on pressure down hole. Here are the variables... the accuracy of the gauge on the pressure truck they use to open these, the density of the fluid in the wellbore (is it fresh water, brine, KCl water, etc).

Regardless, this system has 30% market share in North America and even higher in Russia and other parts of the world...

Exactly, ya' big ol' spanner!!! :)

Don't forget elevation changes. A curve like Turn 8, 8A and 9 at Laguna Seca can cause your tires to change psi and hence throw you off the gawdarn track!!

Where would one get a pressure gauge calibrated? When I worked in the lab our load cells and torque wrenched were sent out to calibration every few months and before and after every big test program, but we never used air pressure gauges.

Tire vendors at the track often have one set up for teams to use. In everyday life, I have no idea.

.

Tire Rack also sells the Intercomp digital tire gauge that is supposedly calibrated and tested. Maybe Intercomp would test and re-calibrate it's gauges if they're sent back in?

To sum it all up-compared the new to the old-I threw 4 away.
It is not scientific-law of averages.
I now have three that read the same.

I have 2 sets of CIS gauges, both purchased at the same time (they sent me 2 by mistake and told me to keep it). at higher pressures they DO NOT measure the same psi.

I have thought about the same with a tire pressure gauge since I just bought a nice one to go racing with.

I figure its all relative. that is, if you determine 20psi is what you need for cold pressure, then as long as you ONLY use that gauge, you will never know or care if it is accurate or not. you just need it to be consistent.

It doesn't matter if they are digital or analog, you will need to calibrate them against a known standard.

I flatten all four tires...get a zero reading first on all....digital or analog. Tires must be cold to ensure accuracy....YMMV.

How do you calibrate a gauge?

If yer not setting race tire pressure....just check a new one with your four tires. I want a consistent reading....say at 35 PSI....the actual accuracy of the #...ball park close is OK enough...for me.

Calibrating is when you can dial it in to be correct.

I can use the super computer between my ears and get the same result...as long as it is condistent....

Calibrate me now....or calibrate me later :)

Most good gauges have screws for changing/adjusting the zero and span. Cheap ones will not.

I'm screwed ;)

Don't remember the tire-gauge brand but the dial says Ashcroft on it.
It is very accurate!
My mechanic gave it to me when i started autocross. Told me accurate tire pressures are very important.

Someone needs to do an R&R sudy....

Like this one ??
:D

http://forums.pelicanparts.com/uploa...1562605206.jpg

There’s a couple of ways of calibrating them . Most common being Dead weight , or a calibrated by pumping against a calibrated “base gauge “ or calibrated transducer and fluke etc
Never put my tire gauge on a deadweight , but calibrated against a crystal when new and it was dead on .
Edit : it’s a long acre btw

http://forums.pelicanparts.com/uploa...1562605206.jpg

You would have to go back to first principles. Get a Tube with a piston in it - like a tire pump. Calculate the area of the piston, say it’s 2 square inches. Connect your gauge to the hose, put weights on the handle 100 lb would give you an accurate 50 psi.

IIRC, NIST uses manometry for this range of pressures.

Here is a scientific instrument house:
https://www.coleparmer.com/p/nist-traceable-pressure-gauges/59678

I dunno what the engineers use. But I do know you can git as deep as ya wanna with this...

And all this science I don't understand .
It's just my job five days a week .