Thread: TPMS problem
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Old 01-07-2009, 09:52 AM   #4
Norm Peterson
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2008 Ford Mustang
 
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Join Date: Feb 2007
Vehicle: 2008 GT Premium
Location: Delaware Twp, NJ
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Something isn't right. The system is not supposed to go off until the pressure in one or more tires is a few psi less than the door sticker inflation number. No real tech, but I don't think many people have their TPMS go off even if they're 4 or 5 psi low. The TPMS standard mentions "25% below" as the maximum amount low before the TPMS must alert you.

How accurate is the gauge that you were using? Service station air towers were notoriously inaccurate, and I doubt that the newer machines that you have to pay to use are any better (if they're even as good). Even the gauges you buy for yourself vary a bit. I've got three, not counting the ones you read the numbers off the little stick that gets pushed out. Two of those agree within about half a psi most of the time, and the third consistently reads a couple psi higher.

Those 34 and 36 psi numbers may not apply to your tires. I think the 16" base tires may require 35 psi (MVMS document), while the OE 17" and 18" tires only need 32. Maybe somebody who has the 16"-ers or a factory service manual handy (or maybe even an owner's manual) can verify this. Point being that whatever pressure somebody else needs may not be what you need.


Norm
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