I wonder how accurate the TPMS display is supposed to be ... Mine invariably shows 1psi lower than my gauges (and I have several that all agree with each other).

I've taken the position that if I have more than one gauge that all read the same, I will trust them before I will the TPMS. Not that 1psi is terribly critical, but when you're talking 30psi as specified in the manual, you're looking at 29 on TPMS, and a little cold snap can light up the warning light. Nevertheless, I want to run 30.

Anyone know if the TPMS is somehow scientifically accurate, or is it a close ballpark kind of thing? Any way to adjust the TPMS readout?

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1 psi is pretty close.

 

Well, it's a 3.33% error. The analog gauges I have seem to be a good bit less than 1% "off" from each other, and they're not high-dollar precision instruments by any means.

But that's part of my question, I guess - is the TPMS calibrated to any significant degree of accuracy, or is it intended to be "just close"?

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3.33% is a pretty small deviation. The manual states that the pressures should be checked manually at least once a month. I've found the TPMS readings to be pretty close to the tire gauge readings. Is 1 psi really that big a deal? Maybe you should be filling your tires with nitrogen if 1 psi is that important.

 

I just recently checked mine with a digital gauge and it was spot on with the TPMS.

 

I just adjusted my pressures for the colder weather a few days ago. The cold tire pressure via TPMS was right on what I got with my analog gauge except in one tire, in which it was 1 psi lower.

 

I checked my tires with a gauge just last night. All were all 2-3 PSI low so I pulled out the compressor and brought them to where they should be. Started the car, gave the TPMS a couple of seconds to register and they were spot on with my gauge.

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It is almost impossible to get the readings to be the same on your tire gauge and on the TPMS as you are talking about apples and oranges. The problem is with the gauge and not the TPMS. The condition you are measuring with the guage is different than the condition in the tire. The TPMS is correct and that is what you should go by.

 

BTW, if you measure your tire pressure in a 70 degree garage and it is going to be 40 outside you should inflate the tires to 35/32 for proper pressure when outside using the 1 psi for each 10 degrees of drop of temperature. Warning: You should never inflate the tires beyond 39 psi regardless of the temperature.

 

Here is the explanation from Acura about the difference from the May 2006 TSB: http://www.in.honda.com/Rjanisis/pubs/SN/B060500.PDF

 

Thanks, Rex - that's interesting. I assumed the pressure the TPMS displayed was the difference between "inside" and "outside" pressure, just like the gauge. I'm at about 650 ft. altitude here in North Texas, so that might account for the 1 psi difference I see.

HOWEVER ... I have to wonder if your advice to go by the TPMS is correct. I don't think tire mfr's issue pressure recommendations based on mean absolute, but rather the differential between atmospheric and internal pressures. I'd therefore tend to stick to my usual belief that a really good tire gauge is what I should be using. After all, If I go by my TPMS, I'd be running comparative "gauge pressures" of 29 psi when the TPMS says 30, and I just don't like seeing gauge pressures below 30.

But thanks for clearing that up.

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