Air pressure gauge comparison

[Twinsig]

From 2005, interesting.

 

www.mcnews.com/.../200511gauges.pdf

[Guest Kakugo]

I had a number of gauges in my life.

The best one by far was a Michelin-branded unit made by Eurodainu, an Italian manufacturer specializing in precision industrial gauges. Incredibly accurate, needed very little in way of adjustment over time and served with distinction for many years until an accidental drop put an end to it.

Next I had a gauge made by a local pneumatic supplier using high end parts. Very, very expensive and very, very inaccurate. Quarreled with them for quite a while because of it.

Now I use a cheap digital gauge I bought at a local car parts store. Very, very accurate, solar powered, can be easily read and can switch between psi, kPa, bar and kg/cm2 at the push of a button. Only problem is it automatically turns off after one minute...

 

 

[12R12RT]

Might be just me and my computer (though I tried in both IE and Chrome) but that link takes me to the main MCN page, not to an article on air pressure gauges.

 

edit: I found this link:

http://www.mcnews.com/mcn/technical/200511gauges.pdf

 

Tom

[Peter Parts]

Funny thing, the most important factor (after form factor) is variation in readings (AKA standard deviation, range, inter-quartile range, or any number of other possible meaningful stats that the MCN Excel spreadsheet computes with no effort on MCNs part), not accuracy.

 

Accuracy means nearly zilch. You go for a ride and decide what reading on your little gauge feels right. Doesn't matter what Pirelli thinks. Doesn't matter much if your gauge is a bit high or low. No other way to do it, unless you trust all the air pumps at all the gas stations.

 

You want the gauge to be repeatable, consistent and stable.

 

Another wrong comment is about checking your pressure before each ride. If you did that, you'd need to restore the air lost during the check every second ride.

 

Not sure it is correct to oil a pencil gauge. Don't know if they rely on known friction wet or dry?

 

Valuable to have that kind of consumer testing. But a fine line between reliable testing and too-quick-and-dirty with just two tries at each of three settings (which wasn't reported anyway). Better would have been six tries at 36 psi.

 

Ben

[na1g]

I suspect (without any empirical evidence) that there is some sample variability, especially in the lower-cost gauges. For the MCN test (2005, so it's pretty old info) to be of real value, they needed to test more than one of each model.

 

My garage gauge is an old Brookstone analog dial unit that has remained accurate. On the bike I carry a digital that was a freebie from an AMA membership renewal, and I also use a no-name pencil gauge that came in the tool kit of a 1993 Kawasaki Concours. All three gauges match within .5-psi. I also had a nice NAPA pencil gauge that also matched but I dropped it into a port-a-potty and decided not to retrieve it.

 

Checking your tire pressures frequently is probably more important than absolute accuracy, at least for road riders.

 

pete

[12R12RT]

...

Not sure it is correct to oil a pencil gauge. Don't know if they rely on known friction wet or dry?...

 

No, they contain a small piston backed by a spring. Air pressure against the piston moves the indicator out, opposed by the spring.

 

Tom

[Peter Parts]

...

Not sure it is correct to oil a pencil gauge. Don't know if they rely on known friction wet or dry?...

 

No, they contain a small piston backed by a spring. Air pressure against the piston moves the indicator out, opposed by the spring.

 

Tom

 

... and some I have operate on momentum with no spring. Dunno if that is old or contemporary design but obviously vastly easier to use a momentum type than my springy kind because the springy kind lose their reading the instant you lift the pencil gauge from the tire to your eyeballs, a key undesirable feature of a bike gauge.

 

Another aspect missing from the MSN evaluation is a human-factors issue that might be called "readability" or resolution. With some pencil gauges, the continuum from say 36.0 to 38.0 might be less than one-eighth of an inch. Not useful when you are lining up a reading with the but-end of the pencil.

 

B.

[Selden]

I have used digital pressure gauges for the past decade or so, and I have never observed a variation of more than 0.5 psi among any of them. But, as Peter writes, the most important thing is finding the pressure that is right for you and your bike, and having a device whose behavior is predictable. The only problem I have ever had with a digital gauge was accidentally switching it from PSI to BAR, and wondering where all the air had gone in less than 24 hours....

[12R12RT]

I'm only familiar with this type of pencil gauge.

 

http://auto.howstuffworks.com/pressure-gauge3.htm

 

The animated gif is incorrect; in the third sequence the piston would be forced back to it's original position by the spring.

 

Have you a similar reference for one that works on momentum?

 

Tom

[SAAB93driver]

I like the Accu-gage with the chuck and the deflator button. But it isn't very compact.

 

http://www.ghmeiser.com/specialtydial.htm

 

 

[elkroeger]

I like how a few of those $2 pen type gauges actually rate pretty well in the article.

 

Real men, however, don't need anything more sophisticated than a greasy old Tire Buddy.

[elkroeger]

I don't understand the "momentum" type either.

 

The best I can figure out, is that it's a regular spring loaded pen type gauge, only the sliding indicator part is not directly connected to the piston. So you can remove it from the valve and the thing doesn't immediately slide back into the housing - thus allowing you to read it at your leisure. I thought pretty much all of them worked like that. But that doesn't really have anything to do with momentum, as far as I can tell. Someone enlighten me.

[12R12RT]

...Real men, however, don't need anything more sophisticated than a greasy old Tire Buddy.

 

I take it, then, that I can carry one of those clipped to the RT and explain that "no, it's not a weapon, it's for checking my tires". That thing's more useful than a 6-cell MagLite.

 

Ima get me one...

 

Tom

[Peter Parts]

I don't understand the "momentum" type either.

 

The best I can figure out, is that it's a regular spring loaded pen type gauge, only the sliding indicator part is not directly connected to the piston. So you can remove it from the valve and the thing doesn't immediately slide back into the housing - thus allowing you to read it at your leisure. I thought pretty much all of them worked like that. But that doesn't really have anything to do with momentum, as far as I can tell. Someone enlighten me.

 

So we have Tom Schmitz who doesn't believe a "momentum" pencil gauge exists and Elkroeger who thinks pretty much all of them work like that (or something like that). At least Elkroeger didn't challenge Tom Schmitz to provide a "reference" to prove they don't exist, like the challenge Tom Schmitz posted.

 

The distance that the measure-rod pops out of the pencil shell is determined by the mechanical whatzis of the system. And that is why oiling the measure-rod will influence the reading. I can't imagine it is a trustworthy way to make a gauge, but then I say the same thing about a monumentally disfunctional design like the Paralever.

 

Ben

[12R12RT]

Ben -

 

I think you misunderstood me.

 

That was not meant as a challenge, but rather a request for information about something I have no knowledge of. I'd like to learn about it.

 

You've been riding for nearly as long as I've been breathing, so there's no doubt in my mind you've seen, heard, done, and know stuff I can't hope to. It was in that spirit that I posed the question.

 

Tom

[elkroeger]

Hmmm...

 

Yeah, I didn't get any challenge or angst out of Tom's post. Seemed like an average request for more info.

 

I am still curious about it, at any rate.

[tallman]

I like how a few of those $2 pen type gauges actually rate pretty well in the article.

 

Real men, however, don't need anything more sophisticated than a greasy old Tire Buddy.

 

 

Real men use a remarkably similar device.

WW I trench club

it checks soundness and has an instant deflate accessory.

[Malthound]

On a personal note, with my first bike (an ST1100) and when I was just learning about this sort of thing, after blowing though a set of tires in under half the mileage I would have expected I checked the pressure with two pen gauges from my toolbox against the one I carried on the bike and found a 4 pound variance between them. Even worse, I checked it against the gauge on my compressor hose (the classic gas station kind) and found that to be over 6 pounds off the average of the other three. I bought an analog gauge with a thumb bleeder and checked it against a friend's high-dollar digital and found it to be dead-on. Not sure what any of this says, but I tend to agree with the previous advice that settling on one gauge and referencing it against the bike's performance, rather than focusing on the exact accuracy might be a good general practice.

[12R12RT]

Here's an odd thing.

 

My go-to gauge (I've probably got a dozen of various kinds and quality around the house) is a really cheap pencil type that was a marketing give-away for GMAC Mortgage. The thing has always been dead right.

 

I thought it had gone bad, as it was reading four pounds low compared to what my TPMS said, so I checked it again. It was the TPMS that was off. I simply made the mental adjustment when looking at the TPMS read-out.

 

I recently had new tires installed. After the tires were installed the TPMS is now dead right!

 

I don't understand how or why that would be, but surmise that perhaps the things may have sort of re-booted after seeing zero pressure during the tire change.

 

The tire guy's response to my question "How accurate are TPMS?" was "I have no @#$%^&* idea. I pay no attention to them. I just use the same pencil gauge until I lose it or some rat bastard steals it."

 

Tom

[Paul Mihalka]

TPM's main job is not to give a tire pressure reading but to warn you for a impending problem.

[12R12RT]

Agreed, Paul, but the interesting point is how they went from being off by 10% to being right on. They've stayed that way, too.

 

Tom

[SAAB93driver]

TPMS on my Saab 9-5 puts pressure numbers for each tire on a display. It went haywire once giving false readings. I "reset" it using a procedure in the manual - basically tell the car you are restting, then let out air of each tire in a prescribed order till horn beeps and it has been dead on ever sense.

 

Long story short, maybe that is why your TPMS is reading accurately now after replacing tires.

[dirtrider]

Here's an odd thing.

 

My go-to gauge (I've probably got a dozen of various kinds and quality around the house) is a really cheap pencil type that was a marketing give-away for GMAC Mortgage. The thing has always been dead right.

 

I thought it had gone bad, as it was reading four pounds low compared to what my TPMS said, so I checked it again. It was the TPMS that was off. I simply made the mental adjustment when looking at the TPMS read-out.

 

I recently had new tires installed. After the tires were installed the TPMS is now dead right!

 

I don't understand how or why that would be, but surmise that perhaps the things may have sort of re-booted after seeing zero pressure during the tire change.

 

---

 

 

Afternoon Tom

 

It is sometimes difficulty to use a hand held tire pressure gauge to directly compare TPMS air pressure to a stand alone handheld gauge.

 

There many types of OEM TPMS systems--

 

Some (most) TPMS also monitor temperature & show CORRECTED tire pressure based on the air temperature inside the tire. A lot of those systems use 20°c (68°f) as the base pressure vs temperature. That means the only time a handheld tire gauge could directly compare to the vehicles TPMS readings would be at 20°c (68°f).

Without this system drivers would be required to know the air temperature inside the tires to know if the pressure they are seeing on the dash readout is correct for the situation.

 

Depending on the TPMS type-- some only give real time pressures after the vehicle is moving to save the battery life in the wheel sensors (most have non replaceable batteries) . When sitting still they only send an update signal every few hours or (long period intervals). Others shut down completely & only come alive when a transmitter near each wheel tells the sensor to start transmitting at key on.

 

There are also people induced reading issues-- like some drivers (or service facilities) that rotate their tires then don't do a sensor relearn after the rotation to tell the TPMS that the L/F is now on the R/R, etc. The system still appears to work as there is a tire pressure showing on the dash read out but the tire position vs pressure is incorrect.

 

[12R12RT]

dirtrider -

 

Thanks for that information.

 

My pressure checks/settings are always done cold, and the noted differences were when cold. It's impressive how hot tires can get!

 

The mental was always when underway, as in "OK, the TPMS says they're at 38, so that really means 42, so all is well".

 

Tom

[Peter Parts]

Due to circumstances beyond my control (I am referring to the weather), I am obliged (by my wife) to spend time in Florida.

 

As much as I'd like to fly to Toronto tonight to enjoy the -20F evening breeze, put the trickle charger on my machine for a few hours, and assemble my collection of rusty pencil gauges from the Salvation Army store, today is my charming wife's birthday and I can't make it.

 

But as soon as the opportunity arises, I will respond to Tom's and Elkroeder's interest (as well as my own) to take any "stick out non-spring" pencil gauge to be X-rayed, MRI, fMRI, DNA, and destructively tested by way of re-engineering in order to gain insight into the secrets of its fabrication and any Cabala incantations inscribed inside the case.

 

.... unless somebody who knows a lot more about it than I ever will posts the secrets and saves me the trip home.

 

I like this thread: we all agree that it is repeatability and ergos that matter, not absolute accuracy. Yup, you stick with one gauge; and you rely on a well-calibrated backside as the reference standard in case you change gauges.

 

Ben

[NCStephen]

Here are my two cents worth on this.

 

I was starting to get a bit anal about gauges and accuracy. So I went from cheap pencils to more expensive ones and then I figured nirvana and went digital.

 

What I found was that at odd times, perhaps when hot in the saddlebag the digital would read things that where not there. Sometimes after reading it would show 13 lbs when disconnected. The pressures then would change and I would have to do multiple readings. I got another and the same anomaly would show up from time to time. So taking a reading on the front twice would tend to lower the psi 0.5 and I might do it 4 times before I was satisfied.

 

So what I realize I am looking for is a confirmation that the tire is within a set familiar range. On cold days I use a lower pressure. On hot days perhaps a higher one. Load and ride style for the day also come into play (a sporty day verses a loaded up slab day). What I am looking for based upon my experience is that the tire will warm enough to gain 10% more psi than when cold. Experiential then I have learned that I want a harder or softer tire for the day based upon that desire. The gauge then I really want is to just give me the same markings for the same pressure over time (if it is always 2 lbs high or 2 lbs low I learn what that gauge consistently reads for the tire temps desire). For this I depend upon using the same basic good quality pencil gauge. It packs easier, is more convenient to get to the front stem around the rotors and seems more trustworthy over time and I get my reading easier with less air loss.

 

So the digital gauges are in a drawer somewhere, each bike has a pencil gauge stuck in an easy to retrieve location.

 

I haven't had any experience with TPM on any of the bikes or cars yet.

 

NCS