Vlke

Hey guys,

Not sure if this is normal but I noticed the tire pressure reading on the dashboard is significantly different than the reading I get from the air pressure gauge of the pump I use at gas stations. For example, the suggested pressure is 220kpa or 32 PSI. When I fill my tires to 32 PSI as per the gauge, the car would indicate that I'm at around 270 kpa. That's about 39 PSI. I've been to different gas stations and they're all showing the same. Is there something off with my TPMS? I also notice the rear left tire pressure is almost a bit lower than the others, about 8kpa or so after bit of driving. Anyone else experience this? Thanks!

spoiler900

Its possible something is wrong. In the owners manual under the TPMS it does say to manually check it with other tools and not to rely on your tpms screen. I would try it a few times and if it keeps turning up with different numbers I would ask the dealer to install new sensors.

RDX-Rick

It should be noted that a 10 kpa change in pressure is equivalent to only 1.45 change in PSI. In other words if you measure in kpa you can notice very small pressure changes.

I purchased a digital gauge that reads in kpa in order to take advantage of the more accurate kpa scale. I set all 4 tires of my RDX to 255 kpa (very close to 37 PSI) and the TPMS readings were all 254-255 kpa. I recently installed my winter tires and wheels with new TPMS sensors, and each of those 4 sensors also read 254-255. So after using 8 different OEM sensors I would say they are very accurate.

So what could be wrong with your readings? It's unlikely you have 4 defective sensors, but then are all the gas stations wrong as well?

I suggest buying a good quality digital gauge that reads in kpa and consider that as gospel ( $26 at Canadian Tire).

Also you need to take your readings early in the morning when the tires are cool, and sunlight has not yet hit the tires. Often when I get into my RDX I notice the tires on the sunny side of the car can be 10 kpa higher than the shady side of the car.

Also after driving for a short time all 4 tires will increase in pressure. The fronts will rise about 10 kpa higher than the rears, which I assume is because of the extra weight they carry, and the extra flexing of the sidewalls due to steering motions.

Vlke

I normally wait a while (4-5 hours or overnight) before driving to a nearby gas station which is about a few mins away to fill up air. I really don't know why the readings are so different. I guess I can buy a digital gauge to check. I went to 3 different gas stations, I filled it up to 32 psi but the car will show at least 270 kpa. To get to 230-235 kpa where I want, I have to drop the pressure back down to about 30psi reading which in reality that's only 207 kpa or so.

I also can't understand why the rear left pressure is always a bit lower than the rest. Unless there's a tiny leak?

RDX-Rick

If it reads the same as the other tires imediately after filling up and only drops afterwards, I think you may have a leak.

You say it drops 8 kpa after a bit of driving. The fact is, that in normal conditions tire pressure should be rising after a bit of driving.

At this point you may have a leak, or a faulty sensor, but if you don't own your own gauge, you can't verify anything by checking them after they have been sitting overnight. You currently need to drive back to the gas station, and you really can't measure pressure with those compressors, all you can do is refill the tire to the pressure set on the pump.

I really recommend the $25 digital gauge from CTC, but if you are on a budget, then the old style pencil gauges are usually fairly accurate. Just make sure it has kpa calibrations so that you can compare the gauge to your dashboard display without pulling out a calculator every time.

CPR

I have a digital 10 year old Sears gauge, that works flawlessly
I check pressure, only in the AM; after adjusting at the gas station, the pressure's always the same;(TPMS, & gauge). Works great on my Goodyear Eagle LS2'S/TLX/SH-AWD/Tech

Vlke

All 4 tires are approximately the same pressure when I'm done. However a few days later I will notice the rear left tire pressure lower than others.

When I drive the car, the pressure of the tires will go up a bit, even the rear left one will go up but the reading is always a bit less than the other tires.

I'll def look into a digital gauge too.

KeithL

I use a motorcycle racing tire guage accurate to 1/2 psi and I set tires to 37psi and TPMS shows 38, I notice same thing in her RDX. I trust the guage as i have used it for a while it it used to match up with my previous edit cars.

Vlke

I guess something like this is fine?

RDX-Rick

Considering the gauge reads to the nearest 1/2 PSI , I would consider that right on for all intents and purposes.

My reason for saying that is from an experiment I did myself.

I once set all my tires to 255 kpa using the gauge. Some of the tires were off by 2-5 kpa according to the TPMS. I slowly bled air from the tires with the highest readings until they all read the same on the TPMS display. Surprisingly the digital gauge still showed 255 kpa in all tires. The reason being that the gauge only reads to the nearest 5 kpa (.7 PSI), while the TPMS can change by 1 kpa at a time.

Mike_TX

The gauges on air supplies at gas stations are notoriously, crazy wrong. They are beat all to hell by everyone and his brother Charlie, and quickly lose any calibration they ever had.

Get a decent gauge and use that instead of funky, abused gauges at gas stations. I have one I bought at Walmart for about $9, and it agrees perfectly with my TPMS. That won't always be the case, and you may end buying more than one before you get an accurate one, but almost any of them will be better than gauges run over, banged against concrete, and flung around at gas stations by people who don't care how they treat them.

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Danny Boy

Is there a way to change the vehicle setting to display PSI instead of Kpa?

I hope that will not change the temperature to read F*.

mapleloaf

I find the Auto Fill alert system in my TLX works great and my pressures are very similar to my hand held. There is always going to be some plus or minus between tires, but if it's minimal, it's usually not an issue.

audioxbliss

My TPMS reads anywhere from 0-3 psi off on any given day. I'm just taking the TPMS readings as more of an "uh oh" warning that something might be wrong rather than trying to use it for accurate pressure measurements.