A lesson in tire Air Pressure.

Markee
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Markee
Edited Date/Time 1/12/2015 3:30pm
Its been about two years since I got back into riding (MX) after about 10 years. Setting up my bike 2 years ago for my first ride at the track, last check on the bike was my tire pressure. I bought a dial gauge from advance auto that releases air from the tire through a push button relief, figured it would be more accurate than my on board gauge on the hand pump.

Fast forward 2 years.....

Indicator light in the truck notified me that my tires needed air from the drop in temperature from the first cold night this fall. Air up the tires use my trusty dial relief air gauge and air first tire to 40psi. Walk around to see what on truck onboard pressure read...

Wait a minute.. 49psi? My heart sunk, has my gauge lied to me for two years on a highly sensitive application like moto tire pressure??

Fast forward 1 week. Bought a motion pro oil filled 0-30psi accurate with in .1 of a psi. First check mx front tire with old gauge, 13psi.. Checked with the motion pro gauge, 21psi!!!

For 2 years i've been ice skating, pushing the front.. blaming it on a lack of talent/age/tire etc..

Back at the track with the correct pressure and I'm having to learn my bike all over, night and day.

Moral of the story? We assume or at least I did that a gauge is a gauge. Its not, check your gauge against a quality unit. Also when buying a gauge get one where half the max psi is where you would need your most accurate readings. I highly recommend the motion pro.

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FGR01
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FGR01 1/8/2015 7:07am
1/8/2015 7:07am
Totally agree on all points.

But 21 psi, man ??? You can feel a 21psi tire with your hand and immediately know it is too much.
Markee
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Markee 1/8/2015 7:15am
1/8/2015 7:15am
FGR01 wrote:
Totally agree on all points.

But 21 psi, man ??? You can feel a 21psi tire with your hand and immediately know it is too much.
Yeah, but I've never been in a habit of pushing on a MX tire, always used a gauge.
TF212
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TF212 1/8/2015 7:34am
1/8/2015 7:34am
I would argue that the built in pressure sensors in your vehicles are just as inaccurate as cheapo pressure gauges. They are there to give you a warm fuzzy but definitely shouldn't be used to get a precise measurement.
Skerby
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Skerby 1/8/2015 11:43am
1/8/2015 11:43am
Your new gauge is has a precision of .1 PSI, that says nothing about accuracy.

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Matt Fisher
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Matt Fisher 1/8/2015 12:52pm
1/8/2015 12:52pm
Skerby wrote:
Your new gauge is has a precision of .1 PSI, that says nothing about accuracy.
It's a heck of a lot better that what he had! Laughing
smoothies862
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smoothies862 1/8/2015 7:09pm
1/8/2015 7:09pm
Skerby wrote:
Your new gauge is has a precision of .1 PSI, that says nothing about accuracy.
so do what?
Sprew
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Sprew 1/11/2015 12:25pm
1/11/2015 12:25pm
Skerby wrote:
Your new gauge is has a precision of .1 PSI, that says nothing about accuracy.
The OP indicated the accuracy was .1, not precision/discrimination. The post has been edited. I assume he was provided this information from the manufacturer and not a result of independent testing (haha). A quick look at the gage pictured indicates discriminations of 1.0 psi. A visit to motion pro's website provides their only claim of accuracy is 1.5 percent of the maximum gage reading. With a 60psi gage, the accuracy is +/- .9psi. Almost a pound. They offer a 30 & 15 psi gage that would deliver .45 & .225 accuracy respectively. Many people have become increasingly demanding of pneumatic gagging, especially with the advent of air suspension. One problem is the loss of air volume required for the testing process. The gage offered by motion pro is a little pricey, but probably the best choice for the normal Joe.

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