Air Pressure Gauge

[SilvrT]

This subject has been discussed before but thought I'd just bring it up once again.

 

After installing my new 130/90 front tire, the scoot felt like it was riding on a flat or almost flat rear tire. Pressure on the front was 36lbs and rear was 46lbs (according to my gauge).

 

I dropped the rear pressure to 42lbs and it seemed to help a lot.

 

While out riding yesterday, I was noticing the same "wishy-washy" feeling again...like every little "high-low" irregularity in the road surface, one tire would want to pull in one direction while the other pulled opposite.

 

I decided to buy a digital tire pressure gauge. Checked the tires and they were at 33.5 front and 37.5 rear. Checked again with the old gauge and it showed 36 front, 42 rear.

 

Fired up the compressor and increased the air pressure according to the new gauge. Not sure of the results yet as I didn't get a chance to take another ride. Will update results after Saturday's run.

 

So, just as an update/reminder .... guys, don't rely on your fav old tire gauge (I'd had mine for at least 10 years...it was one of those round dial with a release kind).

[Squeeze]

Whatever Gauge you use, i'd recommend to cross check it with a calibrated Gauge. Here, all Gas Stations have to have the Pressure Gauge calibrated each Year. The Administration checks this while chekcing the Pumps and eventually put heavy Fines out, if you "forgot" to have the Pressure Gauge Calibration done.

[SilvrT]

I dropped the rear pressure to 42lbs and it seemed to help a lot.

 

 

I forgot to mention, at that time I was riding 2-up but yesterday I was solo.

[LilBeaver]

Just because it is digital doesn't mean it is good, unless you also check the tolerances of the gauges.

 

For example the "Slime" gauges that are sold (with a range of 0-160psi) have a tolerance of +/- 3 PSI () with a resolution of .1 PSI (). Which, for a motorcycle (in my opinion) is totally unacceptable and completely less than useless.

 

For clarity, if your tire was inflated to 40 PSI and you had this particular gauge, slime certifies that the reading with be anywhere from 37 to 43 PSI.

 

Rick, I'd double check your packaging (if you still have it), instruction manual or maybe even the gauge itself, as a decent digital gauge would have that listed on it.

 

Hopefully yours is much better than that

 

I have been amazed at how much of a difference 1 or 2 PSI makes in the tires.

 

 

- As Squeeze suggested, checking against an actual calibrated gauge (if you can find one) is always a good idea.

[SilvrT]

I checked the package and couldn't find anything specific to "slime certification" ...???

 

What it does say is 5 - 99 psi and has a built-in re-calibration.

 

I'll look at the package again tonight when I get home.

 

My main point of this is simply "don't trust you old gauge to be accurate" ... not that any new gauge, including a digital one will be.

 

here is the product I bought...

 

http://canadiantire.ca/AST/browse/4/Auto/1/TiresRims/TireGaugesMonitors/PRDOVR~0095517P/Motorcycle%252BDigital%252BTire%252BGauge.jsp

Edited March 18, 2010 by SilvrT

[LilBeaver]

I checked the package and couldn't find anything specific to "slime certification" ...???

 

What it does say is 5 - 99 psi and has a built-in re-calibration.

 

I'll look at the package again tonight when I get home.

 

My main point of this is simply "don't trust you old gauge to be accurate" ... not that any new gauge, including a digital one will be.

 

here is the product I bought...

 

http://canadiantire.ca/AST/browse/4/Auto/1/TiresRims/TireGaugesMonitors/PRDOVR~0095517P/Motorcycle%252BDigital%252BTire%252BGauge.jsp

 

 

These are pretty good . I had one of these (actually, it is still in my tool box) for about 10years or so, and just last year the little rubber seal on the inside of the end dried up so it doesn't seal on the valve stem anymore -- which, incidentally, is why I was looking for a new gauge.

 

That website claims +/- 0.5 PSI. Which is what the claim on my old accutire gauge was as well. I sure wish I could find one of those down here.

 

With respect to the "slime certification", I don't know if you have the product up there or not, but 'slime' is a company that puts out one of those 'tire sealant' kits that is the goop you put in the tire after you've run something over that is supposed to get you to the next service station.

 

I understood the main goal of your post and couldn't agree more.

I re-read my response and realize that it could have been misinterpreted. I was merely looking to help point out something to look for when one selects a new gauge and to not be given a false sense of security by seeing the digital display. Lots of people would see the fact that a gauge or meter reads to say the 0.1 place - and assume that because it reads that means it is accurate to there as well. I guess I see this A LOT with my students... And I get pretty easily discuted with products that have the potential to be great, then you flip it over and read the fine print and see that type of rating, despite the price tag and the front that claims it is the 'most accurate in its class' or whatever the wording was.

 

Anyways, I didn't mean to hijack anything, steer away from your original point or whatever, just wanted to help make sure people were aware of that fact before hopping into something that won't do what they expect it to (and may or may not realize it).

 

[SilvrT]

Anyways, I didn't mean to hijack anything, steer away from your original point or whatever, just wanted to help make sure people were aware of that fact before hopping into something that won't do what they expect it to (and may or may not realize it).

 

 

no need for apologies my friend... your input is always welcome and generally very informative. was no hijacking that I could see.

[1BigDog]

36 lbs on a front tire seems kinda low anyway.

[SilvrT]

36 lbs on a front tire seems kinda low anyway.

 

36 front & 41 rear is factory spec

[Squeeze]

Not to complicate the Accuracy Thing, but each and every Measuring Device has Tolerance and this Tolerance is measured in PERCENT to the End of Scale Value. That's important, because if you measure Values at the lower End of the Scale the Accuracy goes South pretty quick.

 

So if this Gauge is rated +/- 0.5 psi it's really +/- 0.5 Percent in Relation to the Scale End Value of 99 psi.

 

On a digital Device comes a second Value on Top of that which is one Digit. If the Gauge shows 99.9 psi at the End of the Scale, the last Digit is 0.1 psi. If it shows 99 psi, the last Digit is one psi !

 

So, depending what Value is shown on the Display, the real Accuracy is +/- 0.5 psi plus 0.1 psi = +/- 0.6 psi OR it's +/- 0.5 psi plus +/- 1.0 psi = +/- 1.5 psi.

This means measuring in mid Scale Range at actual 42 psi will result in a displayed Value of 41.4 to 42.6 psi. Or, if there's not Digit behing the Decimal, the Display will show between 40.5 and 43.5 psi.

 

 

As you see, if you measure at the lower End of the Scale i.E. at real 10 psi, the typical Variance is much less accurat than one would expect with only seeing the +/- 0.5 psi Rating.

[SilvrT]

Not to complicate the Accuracy Thing, but each and every Measuring Device has Tolerance and this Tolerance is measured in PERCENT to the End of Scale Value. That's important, because if you measure Values at the lower End of the Scale the Accuracy goes South pretty quick.

 

So if this Gauge is rated +/- 0.5 psi it's really +/- 0.5 Percent in Relation to the Scale End Value of 99 psi.

 

On a digital Device comes a second Value on Top of that which is one Digit. If the Gauge shows 99.9 psi at the End of the Scale, the last Digit is 0.1 psi. If it shows 99 psi, the last Digit is one psi !

 

So, depending what Value is shown on the Display, the real Accuracy is +/- 0.5 psi plus 0.1 psi = +/- 0.6 psi OR it's +/- 0.5 psi plus +/- 1.0 psi = +/- 1.5 psi.

This means measuring in mid Scale Range at actual 42 psi will result in a displayed Value of 41.4 to 42.6 psi. Or, if there's not Digit behing the Decimal, the Display will show between 40.5 and 43.5 psi.

 

 

As you see, if you measure at the lower End of the Scale i.E. at real 10 psi, the typical Variance is much less accurat than one would expect with only seeing the +/- 0.5 psi Rating.

 

Great!! that's it then... I'm trashin this piece-a-junk I bought! :rotf:

[Squeeze]

Great!! that's it then... I'm trashin this piece-a-junk I bought! :rotf:

 

 

No need to trash it right now, just find a calibrated Gauge, and cross check the Pressure your usually operating your Gauge. If it's one or two psi off, you'll see this and operate with the Result.

 

Since LilBeaver brought the Accuracy Thing up, i thought, i put an half Hour of my Life into typing the above Post ...

 

 

 

 

and you just type Trash and be done with it .... :stickpoke::stickpoke:

 

 

 

 

 

:crackup::crackup:

[LilBeaver]

Not to complicate the Accuracy Thing, but each and every Measuring Device has Tolerance and this Tolerance is measured in PERCENT to the End of Scale Value. That's important, because if you measure Values at the lower End of the Scale the Accuracy goes South pretty quick.

 

So if this Gauge is rated +/- 0.5 psi it's really +/- 0.5 Percent in Relation to the Scale End Value of 99 psi.

 

On a digital Device comes a second Value on Top of that which is one Digit. If the Gauge shows 99.9 psi at the End of the Scale, the last Digit is 0.1 psi. If it shows 99 psi, the last Digit is one psi !

 

So, depending what Value is shown on the Display, the real Accuracy is +/- 0.5 psi plus 0.1 psi = +/- 0.6 psi OR it's +/- 0.5 psi plus +/- 1.0 psi = +/- 1.5 psi.

This means measuring in mid Scale Range at actual 42 psi will result in a displayed Value of 41.4 to 42.6 psi. Or, if there's not Digit behing the Decimal, the Display will show between 40.5 and 43.5 psi.

 

 

As you see, if you measure at the lower End of the Scale i.E. at real 10 psi, the typical Variance is much less accurat than one would expect with only seeing the +/- 0.5 psi Rating.

 

 

I looked up what the manufacture claims and the manufacture claims an accuracy of +/- .5% +/- 0.1 PSI. So whoever typed up the website for Canadian tire was not as complete as they should have been.

 

However, there realistically is not enough information available to know how the company determined this particular accuracy number.

 

Really what an end user ought to care about is the precision of the device (provided the end user have a trusted standard measure to compare it to and create their own correction curves to appropriately interpret the reading from the instrument). That is, the ability for the device to reproduce the same reading, time and time again. THEN, one could concern themselves with how close these repeated readings are to the actual accepted value (which is what is known as accuracy). What this particular 'accutire' gauge does is 'calibrates' itself when you put it on the valve stem to turn it on (by pressing it on then taking it off and letting the display show 0.0) then put it back on and the internal electronics compare the differences in the 'readings' to spit out a final reading. So, what really matters is the internal circuitry and how it was programed and what it was 'tuned' for.

 

Squeeze: I am going to have to disagree with you on this. The 'accuracy' that the company reports does not necessarily mean that the value they come up with is the value at the top of the devices range (as you described). That is, in fact, ONE way to report a devices accuracy; but there is no way for us to know what method the company used to produce this particular value for the accuracy of this device. It could simply be an average of many values that were measured over the entire range of the device; or it could be the absolute minimum accuracy that was found in the testing process. Fact is, without more documentation (or testing), we simply cannot know.

 

All of this really boils down to: in order to be conclusive one way or the other, we would just have to find some way to test it against a trusted standard or crack one open and take a look at the internal electronics (which I might do, for kicks, since mine no longer seals enough to get a decent reading).

 

And what really matters to you, SilverT, is that it works well enough to give you the ride that you feel you should have when being inflated to the indicated value.

[LilBeaver]

Great!! that's it then... I'm trashin this piece-a-junk I bought! :rotf:

 

No need to trash it right now, just find a calibrated Gauge, and cross check the Pressure your usually operating your Gauge. If it's one or two psi off, you'll see this and operate with the Result. ...

 

 

-- Unless you are comfortable with the possibility that you could be ~1 PSI off. Then you can just suck it up and deal with it

 

If you worry about it too much, you'll have to also consider how much the pressure changes for the little bit of air that comes out when you put the gauge on and off, not to mention any deviations in the surface and internal tempurature of the tire at the time of testing, as well as ambient air pressure and humidity. For example if you check your tires in your garage that is shaded and cool then roll your bike outside and let it bake in the sun for a while, you are likely to get two [statistically] significantly different readings. By statistically significant I simply mean that you are beyond say 2 or 3 error bars from the accepted tolerance of the meter used to make the measurement to begin with.... I suppose I will stop... For now

Edited March 19, 2010 by LilBeaver
Punctuation and Sepliing

[LilBeaver]

...

 

Since LilBeaver brought the Accuracy Thing up, i thought, i put an half Hour of my Life into typing the above Post ...

....

 

 

By the way, I know that I do appreciate the time and effort that you must put into typing your posts out in English. You provide a lot of great information to our community!!

[Scooter Bob]

36 front & 41 rear is factory spec

 

Is that your RSV owners manual, or the tire sidewall spec? (I don't have my bike handy to check the manual or the avons on it)

 

You put on something other than standard equipment tire (not that there's anything wrong with that).

 

That different width tire could very well require a different pressure to hold up the weight of the bike and provide the proper stiffness to hold up in the corners and such.

 

Just an unrelated to the gauge thought, Scooter Bob

[SilvrT]

Is that your RSV owners manual, or the tire sidewall spec? (I don't have my bike handy to check the manual or the avons on it)

 

You put on something other than standard equipment tire (not that there's anything wrong with that).

 

That different width tire could very well require a different pressure to hold up the weight of the bike and provide the proper stiffness to hold up in the corners and such.

 

Just an unrelated to the gauge thought, Scooter Bob

 

The tire on the rear is stock Dunlop D404 and the spec is from the owner's manual

 

The front tire is a Bridgestone Spitfire S11 130/90-16 and the max pressure for it is 41lbs.

 

Good point you make ... won't get to check out the pressure changes until Saturday.

[Squeeze]

....

 

Squeeze: I am going to have to disagree with you on this. The 'accuracy' that the company reports does not necessarily mean that the value they come up with is the value at the top of the devices range (as you described). That is, in fact, ONE way to report a devices accuracy; but there is no way for us to know what method the company used to produce this particular value for the accuracy of this device. It could simply be an average of many values that were measured over the entire range of the device; or it could be the absolute minimum accuracy that was found in the testing process. Fact is, without more documentation (or testing), we simply cannot know.

 

All of this really boils down to: in order to be conclusive one way or the other, we would just have to find some way to test it against a trusted standard or crack one open and take a look at the internal electronics (which I might do, for kicks, since mine no longer seals enough to get a decent reading).

 

And what really matters to you, SilverT, is that it works well enough to give you the ride that you feel you should have when being inflated to the indicated value.

 

First off, thank you for your Kind Words in the other Posting.

 

I certainly have no Problem with a Disagreement, and to be honest, i didn't get too deep into "new Measuring Methods" and i didn't keep too deep Track in change of Things the last 20 Years. But anyway, to my Knowledge, the Law of Physics haven't changed much in these Matter since.

 

It doesn't matter much what the Seller or the Manufacturer claims and if they describe the Accuracy of their Device right or in a wrong Way or wrong Words. I figure the average Buyer won't care too much about these deep Specifics anyway. This is not a Hi-Tech Device, it's just what it is.

 

What i said doesn't apply specific to this Pressure Gauge alone, it goes for all Measuring Devices for any Kind of Dimensional Unit. Voltage, Current, Temperature, Pressure, Lenght, you name it. There's not one Way or two or even more, there's only that, the Laws of Physics. All analog Devices have it's Class specific Error and the Digitals will have the same class specific Error plus the "last Digit Problem". Not to mention the added Problems of an active Device, such as a Battery powered Device which needs a Kind of Power to do the Job, i.e. Values probably vary with the Battery Voltage.

 

In the End, it doesn't matter too much for the User, his Device may have an out of bound Error or not at the Value he trying to quantify, as long as he wants to compare his Values with other one's Values he needs to be sure he and the other Part measure the with the same Error Margin. Everybody can compare his uncalibrated Values with a calibrated Value and knows the Variance at the given Value. Doesn't matter if the given Value is at the End of the Scale Range or not.

 

Measuring Things like Voltage on the Bike only for myself doesn't care for any Error at all, as long as i use allways the same Device. The Problem will start to occur if i use three different Gauges and get three different Values. Then, it's somewhat important to know how to rate the Error Margins. Or, even more, if i try to compare my Values with other Folks Values like "you should see 13.4 Volts DC or more there" ... That's why Mankind invented Standards and got very deep into this Measurement Stuff ....

[OldBear]

I'd always figured the gauges we buy are somewhat "inaccurate" at best, so I stick with ONE gauge. Start with the factory recommended pressures, and then "play" with different pressures 'till I get what works with the bike in question. Once you've got that reading, as long as you stay with the same gauge you should be ok. Just my 2 cents..

[LilBeaver]

First and foremost: :doh: )

 

 

... but each and every Measuring Device has Tolerance and this Tolerance is measured in PERCENT to the End of Scale Value. That's important, because if you measure Values at the lower End of the Scale the Accuracy goes South pretty quick.

...

So if this Gauge is rated +/- 0.5 psi it's really +/- 0.5 Percent in Relation to the Scale End Value of 99 psi.

...

 

So, after your last post I re-read your original post (quoted above) and thought about it some more and I realized that I had grossly misinterpreted a few of your phrases which, for someone who does error analysis on a daily basis (like me), I immediately over-complicated what it is you were saying.

As far as the last digit 'problem' we both basically ended up saying the same thing.

 

The issue I had was simply with my interpretation of what you had written. I guess I've been doing error analysis too long or something but your "End of scale value" and your later mention of the "99.9" vs "99" is what threw me off. I managed to interpret your comments as to say that the accuracy, quoted by the manufacture, was measured at the extremes of the devices range (which is 5PSI to 99 PSI). When you really were actually simply talking about what is DISPLAYED by the device it self. )

 

 

So, depending what Value is shown on the Display, the real Accuracy is +/- 0.5 psi plus 0.1 psi = +/- 0.6 psi...

This means measuring in mid Scale Range at actual 42 psi will result in a displayed Value of 41.4 to 42.6 psi.

...

 

...

For this meter, the above is correct.

 

 

First off, thank you for your Kind Words in the other Posting.

 

I certainly have no Problem with a Disagreement, and to be honest, i didn't get too deep into "new Measuring Methods" and i didn't keep too deep Track in change of Things the last 20 Years. But anyway, to my Knowledge, the Law of Physics haven't changed much in these Matter since.

 

It doesn't matter much what the Seller or the Manufacturer claims and if they describe the Accuracy of their Device right or in a wrong Way or wrong Words. I figure the average Buyer won't care too much about these deep Specifics anyway. This is not a Hi-Tech Device, it's just what it is.

 

What i said doesn't apply specific to this Pressure Gauge alone, it goes for all Measuring Devices for any Kind of Dimensional Unit. Voltage, Current, Temperature, Pressure, Lenght, you name it. There's not one Way or two or even more, there's only that, the Laws of Physics. All analog Devices have it's Class specific Error and the Digitals will have the same class specific Error plus the "last Digit Problem". Not to mention the added Problems of an active Device, such as a Battery powered Device which needs a Kind of Power to do the Job, i.e. Values probably vary with the Battery Voltage.

 

In the End, it doesn't matter too much for the User, his Device may have an out of bound Error or not at the Value he trying to quantify, as long as he wants to compare his Values with other one's Values he needs to be sure he and the other Part measure the with the same Error Margin. Everybody can compare his uncalibrated Values with a calibrated Value and knows the Variance at the given Value. Doesn't matter if the given Value is at the End of the Scale Range or not.

 

Measuring Things like Voltage on the Bike only for myself doesn't care for any Error at all, as long as i use allways the same Device. The Problem will start to occur if i use three different Gauges and get three different Values. Then, it's somewhat important to know how to rate the Error Margins. Or, even more, if i try to compare my Values with other Folks Values like "you should see 13.4 Volts DC or more there" ... That's why Mankind invented Standards and got very deep into this Measurement Stuff ....

 

Thanks for the clarification. As mentioned above, the issue with significant digits IS what you were referring to, and I mis-interpreted your comments as a discussion of how the 'accuracy' of the device was determined.

Edited March 19, 2010 by LilBeaver
Fixed the quote box

[SilvrT]

I gotta admit guys ... I never imagined in my wildest dreams that my initial post would evolve into such a deep, technical discussion which, while entertaining and educational, is waaayyyyyyy over this old computer tekkie's head and for all intents and purposes, a lot more info than I was looking for LOL ... but hey... it's ALL GOOD

[RandyR]

I've always hoped (not calibration tested) that a 50psi gauge would be more accurate than a 100psi gauge. Thats speculation on my part. But my theory anyway..

[Wanderer]

These are pretty good . I sure wish I could find one of those down here.

 

 

Here it is. [ame=http://www.amazon.com/Accutire-MS-4710B-Motorcycle-Digital-Gauge/dp/B000YQQZCW]Amazon.com: Accutire MS-4710B Motorcycle 5-99 PSI Digital Tire Gauge: Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31yUr0fLSHL.@@AMEPARAM@@31yUr0fLSHL[/ame]

[LilBeaver]

I've always hoped (not calibration tested) that a 50psi gauge would be more accurate than a 100psi gauge. Thats speculation on my part. But my theory anyway..

 

All other things being equal (and this IS a rather rash assumption) the 'same' gauge that reads 0-50PSI vs the gauge that reads 0-150PSI , the one with the smaller range is more likely to be more accurate than the one with the larger range.

 

If you think about this in terms of a 'stick' gauge - where you put the end of the gauge on the valve and the stick pops out of the bottom with a reading on it, one can see very clearly that if you have hash marks every 5 PSI (like on a 0-100PSI gauge) vs. hash marks every 1 or 2 PSI (like on a lower range gauge, ie. 0-50) it is clear to see that the one with the finer resolution (on the stick) is, in fact, more likely to be more sensitive to finer differences in air pressure (ie. more accurate/offer a higher resolution).

 

With the digital gauges, it is a little more difficult to make this type of comparison, because the display (as squeeze and I have discussed) may or may not be representative of what the unit is actually capable of doing. But, on the same level, would be reasonable to assume that your 10-20 dollar gauge with the smaller range has a much better chance of being more accurate than the 10-20 dollar gauge on the shelf next to it with a range of 0-160.

 

 

Here it is. Amazon.com: Accutire MS-4710B Motorcycle 5-99 PSI Digital Tire Gauge: Automotive

 

Thanks!!! Yup yup, last night I found this too... I've got 2 on the way

[SilvrT]

Here it is. Amazon.com: Accutire MS-4710B Motorcycle 5-99 PSI Digital Tire Gauge: Automotive

 

That looks identical to the one I bought at Canadian Tire ...I didn't look at the brand but suspect it's the same.