Pressure Gauge Calibration

[BradHend]

Hi folks, just wanted to remind everyone to not do what I did and maybe save yourself a major hassle on the highway.   
I purchased a $100.00 dial type Snap-On tire pressure gauge last year and before leaving for holidays today, I checked and corrected all tires to 110PSI as I usually do. 
After driving for around 6 hours I unfortunately blew my passenger side inside dual tire on the 401 highway in Ontario.  
Not too much damage thanfully, it broke one of the body panel clips but that’s about it.  East fix.  Guy behind me got blasted with some debris and he did pull over ahead of me to check his car over, but in the end neither of us could see any damage and he said it’s a rental anyways so all good and carried on his way. Ha.
I called every truck repair shop, mobile repair service and only one person had a tire in stock that would fit, but they were closing in 49 minutes when I called them. 
I limped the coach over to them, and he changed my tire.  
Out of curiosity, I checked the tire pressure when he was all done with my Snap-On pressure guage and it was only reading 90PSI. I asked him why so low, and he said it’s a cold tire and I only fill them up to 100PSI if they’re cold.  Fair enough I said, but my guage says it’s only at 90PSI. He looked at me weird, grabbed my guage and tried it.  Sure enough he read 90 as well.  He went and got his guage and it was reading 100 on the money.  We took both gauges into his shop and compared to their calibrated shop air system and sure enough, my Snap-On was reading 10PSI under actual. 
I immediately went out and checked all my tires that were now warm and were set at what I thought was 110 PSI this morning.  Most were now at 120, a couple crept up to 125.  I over inflated my tires and as a result blew a 5 year old drive tire.  
So, long and short, check your gauges against a known pressure.  Such an avoidable situation and I could have just easily confirmed at home with my shop air.  Don’t always assume I guess, even with the brand names.  Lesson learned the hard way. 

[tmw188]

Curious you didn’t say whether you had a tpms to check them against? 

[BradHend]

Do not have a TPMS. 

[Tom Cherry]

10 hours ago, BradHend said:

Hi folks, just wanted to remind everyone to not do what I did and maybe save yourself a major hassle on the highway.   
I purchased a $100.00 dial type Snap-On tire pressure gauge last year and before leaving for holidays today, I checked and corrected all tires to 110PSI as I usually do. 
After driving for around 6 hours I unfortunately blew my passenger side inside dual tire on the 401 highway in Ontario.  
Not too much damage thanfully, it broke one of the body panel clips but that’s about it.  East fix.  Guy behind me got blasted with some debris and he did pull over ahead of me to check his car over, but in the end neither of us could see any damage and he said it’s a rental anyways so all good and carried on his way. Ha.
I called every truck repair shop, mobile repair service and only one person had a tire in stock that would fit, but they were closing in 49 minutes when I called them. 
I limped the coach over to them, and he changed my tire.  
Out of curiosity, I checked the tire pressure when he was all done with my Snap-On pressure guage and it was only reading 90PSI. I asked him why so low, and he said it’s a cold tire and I only fill them up to 100PSI if they’re cold.  Fair enough I said, but my guage says it’s only at 90PSI. He looked at me weird, grabbed my guage and tried it.  Sure enough he read 90 as well.  He went and got his guage and it was reading 100 on the money.  We took both gauges into his shop and compared to their calibrated shop air system and sure enough, my Snap-On was reading 10PSI under actual. 
I immediately went out and checked all my tires that were now warm and were set at what I thought was 110 PSI this morning.  Most were now at 120, a couple crept up to 125.  I over inflated my tires and as a result blew a 5 year old drive tire.  
So, long and short, check your gauges against a known pressure.  Such an avoidable situation and I could have just easily confirmed at home with my shop air.  Don’t always assume I guess, even with the brand names.  Lesson learned the hard way. 

EV or Horse and Buggy.  Sort of depends on what you need and such.

I have a "Trucker's" mechanical Gauge that I bought in 2006 when I had my first MH, a Winnie.  In 2009, I bought the Camelot NEW.  In 2010, I put on the Pressure Pro TPMS.  The sensors on that system were maybe 3 PSI "HIGHER" than what my Silver Flute read.  Fast Forward to maybe 2017. I upgraded to the NEW Pressure Pro and replaced all the sensors and the display.  That is 10 TIRES that I monitor.  THEN, the PP reads exactly the same as the NAPA gauge.

MY TAKEAWAY.  I use the NAPA gauge, COLD in the AM, to make any adjustments.  That is the PROPER time and procedure...  THEN, I turn on the system and let the 3 minutes elapse while all the sensors are "Checking In".  The NAPA gauge is accurate...  OK, I might miss by a pound as the scale is calibrated in 2 pound increments.

BUT, I KNOW that the sensors are OK and I don't use the NAPA gauge as a hammer or tent peg spike...it stays in the front center console drawer...and easy to grab.

I have a background in Lab and Gauge and Quality control...as well as in process engineering and such. I don't have all the GOODIES or lab equipment that I once had access to.  BUT, I often compare the NAPA gauge to the "SLIME" mechanical gauges that I keep in each car.  AND, I often DO compare each vehicles (3) TPMS readings.  All are GM.  All are serviced by the same dealer.  He has a Nitrogen Generator.  It deflates and reinflates the tires and tests the nitrogen content and keeps bleeding off and replenishing until it above 90% (my memory).  I have watched and talked to Tech using it. It has 4 hoses.  You can set each wheel or use one value.

SO, I go home...not ALWAYS, but sometimes use the Car's Slime Gauge.  Each of them are within a pound. These are the ANTIQUATED Round dial analytical. I find they are built like a tank.  Then, I will occassionally use the NAPA to compare.  SO, my NAPA gauge works in the 30's range...as well as the 100's.  I also use a Slime for my utility trailer tires which are 60 PSI. NAPA says same.

Just my comments...  I am very dubious of even HIGH QUALITY digital items....and Snap On should be GOOD....but a digital device has circuit boards and such...and can not take the abuse of my Silver Flute.

Call me BUGGY whip. I watch the DIGITAL on the cars and MH...but also check with the Silver Flute...and it get "correlated" at the lower end against my Slimes...

[cbr046]

Curious what brand tires did you have?

Sorry about the "adventure"

- bob

[BradHend]

Bob, I run all Michelin. Steer and drive 

[jacwjames]

4 hours ago, BradHend said:

Do not have a TPMS. 

I didn't use a TPMS on my Class C

But as soon as I got the DP I bought a TPMS, it doesn't move without it communicating with tires and the tires show good pressure.  I run 105 in my front tires and 95 in my rear. 

[BradHend]

I will likely be investing in a TPMS.  And all new rear tires now.  Don’t wanna deal with that again as I was lucky and could have been much worse.  Steers I just replaced last year so they are good. 
 

[Jetjockey]

The pleasure of a good Tpms is there are very accurate and you check tire pressures before you drive while in your drivers seat. Alarms can also be set to warn  of pressure issues. Checking tires with a gauge can eventually cause the valve seat to leak. I have truck shops that will not routinely pressure check tires for that reason. It is great peace of mind to see tire pressures while traveling down the road. 

[dl_racing427]

I tried a digital tire gauge, once.  It read different every time I used it.  I couldn't trust it, and threw it out.

I have several high quality dial type tire gauges from Longacre Racing and I think G-Force, in 30, 60, 100psi, and a 220psi from Amazon.  I also have one of the cheap imported dial types in each car.
I've found the old stick types to be less than accurate, but all my dial types check pretty close, within a couple psi.
I built a leakdown tester with high quality NoShok liquid filled gauges that I use to test gauges and pressure sensors.
 

[96 EVO]

27 minutes ago, dl_racing427 said:

 
I've found the old stick types to be less than accurate, but all my dial types check pretty close, within a couple psi.
 

Yeah, I've retired all my old 'stick' style, in favor of a dial gauge I put together!

[jacwjames]

I have both a dial and digital gauge.  On the coach I'll fill the tires to the desired pressure + 2 psi.  I use a TST507 TPMS.  I'll screw the sensor onto the tires and then check pressures using the display on the TPMS.  Since I'll loose a little air screwing the sensor on I may be at the desired pressure, if not I'll unscrew the sensor and let it bleed out a little air until I'm at the right pressure. 

Only issue I've had is when I set the pressures in +80F temps in TN and travel north.  On really cold mornings the pressure may drop to below the low limit and the alarms starts to blare, not fun.   If I know I'm going to be in cold weather for awhile I'll redo the tire pressures up knowing that I may have to drop pressures when I get to higher  temps.  

I also carry a thermo gun, occasionally I'll pull it out and temp all my hubs & tires looking for any outliers that are higher then the rest.  I'm looking for any signs of failure, high temp on one wheel may indicate a problem.  Taking advantage of some of the newer technologies is a no brainer.

 

[dl_racing427]

18 hours ago, jacwjames said:

I have both a dial and digital gauge.  On the coach I'll fill the tires to the desired pressure + 2 psi.  I use a TST507 TPMS.  I'll screw the sensor onto the tires and then check pressures using the display on the TPMS.  Since I'll loose a little air screwing the sensor on I may be at the desired pressure, if not I'll unscrew the sensor and let it bleed out a little air until I'm at the right pressure. 

Only issue I've had is when I set the pressures in +80F temps in TN and travel north.  On really cold mornings the pressure may drop to below the low limit and the alarms starts to blare, not fun.   If I know I'm going to be in cold weather for awhile I'll redo the tire pressures up knowing that I may have to drop pressures when I get to higher  temps.  

I also carry a thermo gun, occasionally I'll pull it out and temp all my hubs & tires looking for any outliers that are higher then the rest.  I'm looking for any signs of failure, high temp on one wheel may indicate a problem.  Taking advantage of some of the newer technologies is a no brainer.

 

There's no need to adjust tire pressures down due to hot weather.
The lower the initial pressure, the more pressure rise you get when the tires are in operation.
You can always set the pressure in cold weather, note the pressure when it's warm, and use that as your cold pressure in summer.
A few psi above the ideal pressure will not cause a problem, but a few psi too low can cause excessive heat in the tire, which is what eventually causes failure.