TPMS readings compared with manual readings

[bipock]

Had my new-to-me tires put on Friday with my TPMS sensors transferred over. Tech told me he filled them to 38PSI per the door. TPMS showed them to be 40-41. Rode around all weekend and paid attention to the readings and took some random readings, both hot and cold, and found that the TPMS system was almost always 3-4 lbs. higher than the gauge reading.

Manually took the tire pressure down this morning to 35 PSI on all four tires after letting it sit all night using the gauge. Noticed they were measuring 40 when I first started driving and eventually dropped down to 38 after 20-30 seconds or so.

Anyone else notice this difference? Do you just make a mental note that the sensors are "x" lbs higher to make sure your pressure is consistent or is there something wrong there? Or do you ignore the TPMS readings?

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[Reinen]

There is an old saying, a person with a tire gauge always knows their tire pressure. A person with two gauges is never quite sure.

Tire pressure gauge discrepancy has been a thing as long as tires have been around. Can't say which one is off slightly but keep in mind that TPMS is read with 4 sensors while your manual readings are read with one.

 

[GATORB8]

It's hard to identify which tool (TPMS, Pressure guage) is correctly calibrated and what tolerance is.

IIRC, tolerance is based off full scale, so in my example I have a Jaco FlowPro 100 PSI guage with a +/- 2% tolerance, so it should be within 2 psi of accurate (2% of 100 PSI). That Jaco reliably reads 2 psi higher than the TPMS at both 15 and 32 psi (my air down/air up PSI respectively). In reality, I have no idea which one is right, but seems that the TPMS can be dead on and the Jaco can be off within tolerance. Note, supposedly dial gauges are more accurate in the center of the range and are closer to max tolerance at the low and high ends of the scale.

I've swapped to a 60 psi gauge since for my new air setup, but haven't had a chance to compare yet. The 60 psi guage is 1.5%+/-, so it should be within 0.9 psi.

 

[Mikester86]

I find the Jeep’s TPMS readings to be about 2 pounds more than my gauge. I adjust accordingly.

 

[srt20]

I only use gauges as a reference or comparison. I dont care if its accurate, just as long as its consistent and repeatable.

If your tires ride right and show proper wear, pass the chalk test, then use that number.

I have pencil gauges in each vehicle for that vehicle. The one for the Jeep reads 28 psi when the TPMS reads 29. Close enough. If I want it softer I lower it however much I want. If I’m freeway driving and want mpg I raise it to 35 on the pencil. That reads 36-37 on the tpms.

If someone were to use a “certified be all end all” gauge on my tires and told me my actual Tire psi was 50psi when my pencil gauge reads 28 psi I would still run my tires off my pencil gauge because that’s what my Jeep likes.

btw I mainly use tpms to keep and eye out for a slow leak in a tire.

 

[Carolina Jeeper]

I have a calibrated tire gauge that reads what my TPMS displays. But it never has matched my cheap dial gauge I carry in my Jeep tool bag.

Those gauges that don't have the ability to be calibrated are going to disagree with almost anything you compare them to.

 

[Jim1964]

QC is almost certainly tighter on OEM TPMS sensors than consumer grade retail tire gauges. I have a whole collection of various gauges in several vehicles and they vary by ten percent or so.

I also have a good calibrated electronic gauge which is within a percent or two of the TPMS sensors on the vehicles I’ve used it on.

 

[roaniecowpony]

All the above concerns led my OCD to drive me to make this. I bought a calibrated gauge and the pieces to make my own tire gages.

The consumer tire gages are all over the place in terms of accuracy.

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