2012 Jeep Wrangler Sport: Which Tire Pressure Gauge is Correct?
January 10, 2013
It was cold, and the tire pressures had recently been dropped on purpose for some light off-roading. It was therefore understandable that the TPMS light had winked on, but I still needed to check and make sure one of them wasn't leaking.
The Wrangler's TPMS system is of the dumb variety, in that it doesn't display the actual pressures on the dash like some others. So I grabbed a tire pressure gauge out of my toolbox.
None of them were lower than any of the others, so I wasn't facing any sort of leak. For fun I decided to grab a couple of other gauges I had lying around.
As you can see, three out of three tire pressure gauges don't agree. Can you guess which one was correct?
The most accurate answer is "I still don't know." None of these have been calibrated using a master gauge. The accuracy of the civilian tire pressure gauges we typically buy is based largely on trust, and as you can see there's little to put one's faith in here.
According to Price is Right rules, the well-worn dial gauge and its reading of 22.5 psi is the closest without going over.
If none are calibrated, how do I know that my beat-up analog gauge is correct?
Well, because a couple months back I reset the trigger point of the Wrangler's TPMS system myself using something called an AEV Procal. This very cool device is meant — among other things — for off-roaders who have fit oversized tires to their Jeeps. Our huge BFGs have much more load capacity than the skinny originals, so we feel safe running them at 28 psi. We certainly feel less discomfort at that pressure.
TPMS systems are typically set 20-25 percent lower than the recommended running pressure so they don't issue too many false alarms, so with that in mind I reset the system to trigger at 23 psi with the AEV Procal.
Since the TPMS light only just winked on before I did this, the analog gauge's reading of 22.5 psi is right on the money and the two fancy-pants digital gauges are out to varying degrees of lunch.
Which makes me wonder: How can you possibly trust any tire pressure gauge you might buy? One of these has a 4.5 psi error. Buy a good one, I suppose. An analog one with a bleed button meant for racers.
Still, this all seems unnecessary when you consider that each of our Jeep's tire assemblies has an accurate tire pressure gauge built right it. It's a pity Jeep didn't see fit to display those pressures right on the dash so we don't have to struggle with something so simple.
Dan Edmunds, Director of Vehicle Testing @ 24, 654 miles