Battery gauges, have dead batteries every time I reach for one... (not that often)...
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I have found the mechanical ones with a square readout tube, to be more consistent than the kind with a flat tube...
... but,.. don't be overly concerned anyway.... air pressure is not that exact ... it changes minute by minute, as tires heat and cool, and barometric pressure and elevation changes...
...a few pounds either way, don't mean... diddly...
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