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'18 Outback 2.5i Touring. 1960 MGA 1600
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Discussion Starter #1
The pressures shown on my '18's instrument panel are all one pound lower than my gauge. I wonder which is correct. Anybody else observe this?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,491 Posts
neither are high quality scientific instruments.

1 psi seems pretty close to one another,.... = :smile2: + :smile2:
 
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Super Moderator
2008 OB Limited 2.5i, Portland OR USA
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6,759 Posts
Even high quality gauges are good to only about +/-2% of full scale (+/-1.2 PSI for a 60 PSI gauge). TPMS sensors, in contrast to gauges, are value-engineered to catch issues with inflation, not act as a precision measuring instrument, as @eagleeye noted. You're expecting way too much out of them.

More info here on gauge accuracy: GAUGE ACCURACY - Winters Instruments
 

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Premium Member
2018 Outback 3.6R Limited; 2" LP Aventure lift, LPA skid plates and small bumper guard, diff breather relocation, subframe skids; Motegi MR118 17x8et32 wheels; Yakima LoadWarrior with extension; ARB
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318 Posts
Like ^^ said, 1psi is not something I'd worry about. At that point, I'd pick one or the other to set pressures to.
 

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2018 Legacy 36R
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301 Posts
One pound is really very close. Remember the pressure will increase as you drive. Also if the sun is hitting one side the pressures on that side may be a pound or two higher.
 

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Super Moderator
2008 OB Limited 2.5i, Portland OR USA
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6,759 Posts
Like ^^ said, 1psi is not something I'd worry about. At that point, I'd pick one or the other to set pressures to.
OP said he was setting it with a gauge and noted that the gauge read differently than the TPMS system. In this case, I'd trust the gauge and ignore that the TPMS sensors were reading differently.

People tend to confuse accuracy with resolution whenever numerical data is presented. In this case, the resolution of the TPMS sensors well exceeds their accuracy.
 

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Premium Member
2018 Outback 3.6R Limited; 2" LP Aventure lift, LPA skid plates and small bumper guard, diff breather relocation, subframe skids; Motegi MR118 17x8et32 wheels; Yakima LoadWarrior with extension; ARB
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318 Posts
Yep, I tend to side with my tire gauge too, and just use the TPMS to notate a difference in pressures (or a change).
 
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