• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

tire pressure gauge accuracy

NutmegCT

Great Pumpkin
Gold
Offline
Over in Other Cars, I posted that my Tire Pressure Monitoring System warning light had come on. Tire pressures were all between 30 and 32 psi. Warning shouldn't have been triggered.

So I wondered about my "slip stick" tire gauge. I took another from the workbench, and lo and behold - it showed 3 pounds under the reading of the first gauge. Took a dial guage, and it showed 3 pounds *above* the reading of the first gauge.

Called my neighbor, who brought his Slime dial gauge, and it showed the tires were all around 26 psi (nowhere near the 30 my first gauge showed). The warning light is triggered when sensors show a tire is 26.5 or less. Using my neighbor's gauge, I upped the pressure until it showed 33 for each tire. Warning light went out.

Heck - I don't even know if neighbor's gauge is accurate!

View attachment 45987

So ... how the heck do we know what tire pressure we've actually got? What tire gauges do you guys use? Have you ever checked for accuracy? Even the gauges on my two air pumps disagree.

grumble grumble

thanks.
Tom M.
 

TR3driver

Great Pumpkin - R.I.P
Offline
You forgot to wonder if the TPMS sensor is accurate ... one of my local tire stores has a poster suggesting they should be replaced every time you replace the tires because they lose accuracy over time.

"Digital" thermometers aren't, really, they just have a digital readout from an analog sensor. If you're talking about an IR thermometer, they are notoriously inaccurate because the reading depends on a surface characteristic known as emissivity. Old aluminum in particular has a very wide range of emissivity; I've seen over 20F variation just by moving where I "shoot" by 1/4" or less.

I wonder, can you even buy liquid mercury any more? Even with mercury, you'd need a 6' column to measure 30 psi with a manometer. Lots easier to just buy a precision gauge. MMC offers gauges with 1/4% accuracy, but they aren't cheap. Wikipedia shows a calibration device that uses calibrated weights on a piston, but I think seal friction would still be an issue there.
 
OP
NutmegCT

NutmegCT

Great Pumpkin
Gold
Offline
Randall - excellent point about the TPMS accuracy. As more cars get TPMS systems, we become more "sensitive" to tire pressure measurement.

Back in the Days of the Ancients, you just used a manual tire gauge to check tire pressure. Perfect for those days, when psi wasn't "monitored" by something you didn't control. There was no Hidden Force behind the curtain, that might conflict with your gauge.

But now, whether or not the TPMS is faulty, you realize you still don't really know what the tire pressure is. You keep changing the psi "until the light goes off".

Some guys ask "what tire psi do you run?" Others answer, and we experiment with inflation vs. ride and control. But we don't really know what the inflation actually is.

There should be a way for us home garage types to verify the *real* tire psi, without an expensive calibration device.

Thanks.
Tom M.
 
Country flag
Offline
A man with two clocks doesn't know what time it is.
I have 5 pressure gauges and the are all a little different. The best thing to do is use only one all the time. If you like the way the drive feels and it tracks well sue that as a guide. Or go to Les Schwab here in Calif. or Costco and compare their reading.
 

George_H

Jedi Warrior
Country flag
Offline
I have yet to find 2 gauges that agree. I have since decided that my old stick type made by schrader in the 40s or 50s is the best.
 

70herald

Luke Skywalker
Country flag
Offline
Wikipedia shows a calibration device that uses calibrated weights on a piston, but I think seal friction would still be an issue there.

Seal friction is a problem, which is why the correct way to use them is to spin the weights. That way the spinning motion breaks the "stickyness" of the seal. But these aren't used for measuring pressure, they are an extremely accurate pressure source. Basically they are just a piston that you place precision weights on them, and they pump up the entire system until the piston lifts up the weights, then as long as the piston is free to travel the weight applied controls the pressure.

I used these in my first engineering job to calibrate very high end (mostly aerospace) pressure sensors. We probably had at least 100 of these systems everything from low pressure using air or N2 up to extremely high pressure hydraulic systems.
 
OP
NutmegCT

NutmegCT

Great Pumpkin
Gold
Offline
Well, I figure that without special equipment, I'll choose the easy way out:

Consumer Reports highest recommendation for a tire gauge goes to ... the envelope please ...

View attachment 46016

(Interesting that of 14 gauges, the two with circular analog dials got the two lowest ratings.)
 

Mickey Richaud

Moderator
Staff member
Gold
Country flag
Online
Well, I figure that without special equipment, I'll choose the easy way out:

Consumer Reports highest recommendation for accuracy in a tire gauge goes to ... the envelope please ...

View attachment 46016

(Interesting that of 14 gauges, the two with circular analog dials got the two lowest ratings.)

Looks good, Tom.

But how do we know their testing equipment is accurate? (Just never ends, does it? :devilgrin:)
 

TR3driver

Great Pumpkin - R.I.P
Offline
Oh c'mon Mick - I always trust what comes out of the Consumer Reports labs ...
I haven't trusted CR since that debacle with the Suzuki Samurai
https://www.aim.org/aim-report/aim-report-a-black-eye-for-consumer-reports/

I also owned one of the cars they rated among the "10 worst in America" and put over 250,000 hard miles on it (including several long trips towing a trailer much larger than it was rated for through the mountains) without ever having the heads off the engine. Not so remarkable today, but it was back then. It would also out-accelerate a US-spec TR6, carry 5 people in adequate comfort, and get 30 mpg on long freeway trips (with the AC running).

Good point about spinning the weights Yisreal. I hadn't thought of that. Of course it just kicks the problem down the road ... how do you know that a 1 kg weight is really 1 kg :D I used to work with scientists that ran around measuring variations in the force of gravity (among other things).
 

PC

Obi Wan
Country flag
Offline
....Good point about spinning the weights Yisreal. I hadn't thought of that. Of course it just kicks the problem down the road ... how do you know that a 1 kg weight is really 1 kg :D I used to work with scientists that ran around measuring variations in the force of gravity (among other things).
Don't laugh. They're important considerations. Weights can be damaged and lose mass or contaminated and gain mass. Dead weight testers need to be calibrated on a regular basis. And yes, you compensate for local gravity to use them.

Kicking it down the road isn't actually a problem. It's just taking its place in a chain of traceability that references a measurement back to primary standards.
 

dklawson

Yoda
Offline
Kicking it down the road isn't actually a problem. It's just taking its place in a chain of traceability that references a measurement back to primary standards.

Agreed. As an end user, you also have to decide with your device "How accurate do I need it to be?".

In my case, I picked up a 1/4%, 60 PSI, surplus gauge which had at one time been provided with traceability. I use it with a "T" fitting to check the calibration of other gauges (both air and oil pressure).

Is my "standard gauge" calibrated? At one time it was... and I will continue to use it to check calibration of other gauges in my service. I use my standard gauge sparingly and will continue to trust that it is within my acceptable window of accuracy. However, until I have its calibration checked by a lab I am just acting on trust.
 

twas_brillig

Jedi Knight
Country flag
Offline
I've got half a dozen or so tire pressure gauges, all with differing readings on the same tire.
The Consumer Reports link above didn't work, but a search came up with "• Two digital Accutire gauges topped the Ratings, the MS-4400B ($10.99) and MS-4021B ($9.99). The heavy-duty dial-type Intercomp 360060 ($55.95) was also very good but is limited to 60 psi.
• The Slime 20048 ($5.99), a dial type, was hard to read, inaccurate when cold, and lost accuracy permanently when dropped onto a concrete floor from a height of 30 inches. " from https://www.consumerreports.org/cro/tire-pressure-gauges/buying-guide
Also ran across this Internet article https://www.superstreetbike.com/all-tire-pressure-gauges-are-accurate-mythbusters
The Michelin MN-12279 advertises that "Gauge accuracy is +/- 1% plus 0.5 PSI ". I figure 1% of 30 psi is .3 psi so they're claiming an accuracy of +/- .8 psi.
Is anyone aware of any other gauges that specify their level of accuracy?
And on a note regards manometers: we've got a VW dune buggy with dual Kadron carbs that apparently require 1.5 to 2.0 psi max fuel pressure. I put a tee into the fuel line downstream of the regulator, did my math, and hung clear plastic tubing off the basketball net and adjusted the regulator until the fuel reached the required measured vertical distance from the carb throat. I remarked on this (with some pride) to another, whose reaction was 'why not use a gauge?' Well, it's because I trust gravity and fuel density. Unfortunately, fresh water gives you 0.433 psi per foot of head so the height of the tubing would be 'significant' and building your own mercury filled manometer is probably a poor idea. Doug
 

twas_brillig

Jedi Knight
Country flag
Offline
I just had a look at the Snap-On Tools site, and all the tire gauges that I looked (pencil type, digital, dial) claimed 1% accuracy. Bothers me that they're all the same (.3 psi at 30 psi; claimed better than the Michelin). Doug
 

PAUL161

Great Pumpkin
Silver
Country flag
Offline
I'm not getting Toms attachments for some reason, no problems elsewhere. ??? PJ
 

PAUL161

Great Pumpkin
Silver
Country flag
Offline
I'm not getting Toms attachments for some reason, no problems elsewhere, coming up as an invalid attachment. ??? PJ
 

TR3driver

Great Pumpkin - R.I.P
Offline
I'm not getting Toms attachments for some reason, no problems elsewhere, coming up as an invalid attachment. ??? PJ
You can try using the link to report it to 'Basil' (our webmaster and all-round Good Guy); but I suspect that CR may have asked to have them removed from this site. They're kind of picky about that.

Here's a link to the original article; but they want you to pay to see the actual test results.
https://www.consumerreports.org/cro/tire-pressure-gauges/buying-guide.htm

(One would hope that their top rated ones would be the most accurate, but that "ease of use" factor could change that. I've noticed that they often don't have the same priorities that I do.)
 

glemon

Yoda
Country flag
Offline
Believe it or not I have about 5 gauges, one digital, none expensive, some very cheap. One day a few years ago I tested them on the same set of wheels, all within a pound or two of each other. Good enough for me. Like engine compression, I don't need absolute accuracy, but do want to inflate all tires (or at least front and rear pairs) to equal pressure. Since I turn both left and right no NASCAR or dirt track "stagger" wanted here.
 
Similar threads
Thread starter Title Forum Replies Date
J MGB Tire pressure for 1980 MGB MG 14
K TR2/3/3A Rear tire pressure when there is an anti roll bar at the front of the car? Triumph 1
K TR2/3/3A Tire pressure and ride comfort? Triumph 9
K TR2/3/3A Optimum Tire pressure for a TR3 daily driver? Triumph 5
madhouse Tire pressure monitoring system [TPMS] for Healey? Austin Healey 0
tahoe healey Tire pressure again Austin Healey 59
NutmegCT T-Series tire pressure? MG 8
NutmegCT TPMS - Tire Pressure Monitoring System Other Cars 9
sundown TR6 TR6 tire pressure Triumph 4
T TR2/3/3A tire pressure Triumph 18
bighealeysource Tire pressure recommendations for tubed tires Austin Healey 4
Nelson Autocross tire pressure?? Spridgets 4
R Glove box tire pressure plate Triumph 5
G Auto cross tire pressure Spridgets 7
Nelson Tire pressure Spridgets 10
1 Tire pressure MG 8
AUSMHLY Correct tire pressure Austin Healey 8
bighealeysource tire pressure with radials Austin Healey 11
D tire pressure question Triumph 8
wkilleffer Good tire pressure for 18570R14 tires on a '74 'B? MG 19
bighealeysource Tire pressure Austin Healey 2
jlaird Tire pressure Spridgets 5
jlaird Lets get serious=tire pressure Spridgets 18
TRclassic3 Tire Pressure Triumph 9
J Tire air pressure Triumph 9
S Tire Pressure and Additives Jaguar 16
A Dumb tire pressure question MG 9
MadRiver Tire pressure? Triumph 8
vping Tire pressure MG 15
C TR2/3/3A TR3A Tire Pressure Triumph 6
Brosky Tire pressure question Triumph 24
P Correct Tire Pressure for 165R15... Austin Healey 2
J tire air pressure MG 6
S TR2/3/3A Tire balance Triumph 14
S TR2/3/3A Anyone cut out the spare tire compartment on a tr3? Triumph 4
T Tire Age Austin Healey 14
R 2500M Inner Fenders - are they the same as a Vixen 2500? (Also Tire Size) TVR 3
Frameman 1949 Tire Options Austin Healey 16
T TR6 TR6 Tire Pressures Triumph 2
NutmegCT Tire pump in reverse? Restoration & Tools 5
prb51 BN6 Wheel/Tire Combo Austin Healey 26
JohnGone Wanted Q: Small Boot, Small Spare Tire? And, Jack needed. MG Classifieds 2
F TR4/4A Tire saver ramp recommendations Triumph 10
D Wanted Austin healey Tire - used Austin Healey Classifieds 4
Bocaray TR2/3/3A Centred Tire Triumph 3
H Wanted Need Spare tire rod BJ8 Austin Healey Classifieds 1
S For Sale Tire for Sale (155SR15) Triumph Classifieds 3
F TR2/3/3A Spare tire cover Triumph 8
S TR2/3/3A spare tire compartment holes for modern license Triumph 8
Mark Bailey Old tire rule? Restoration & Tools 5

Similar threads

Top