PDX991

Probably a stupid question but my TPMS menu says my tires are about 6 - 8 lbs higher than what my gauge says. Is there a way to calibrate them?

I had this problem on my Boxster too.

Thundertub

Probably a stupid response, but have you tried other tire gauges to see what they read?


I want to add that my TPMS readouts are all over the place until the tire temperatures warm up and settle. Then they match my quality tire gauge. I do know that you should not use the TPMS readouts when the car has been sitting. Even says so in the owners manual.

Your tires will rise many psi while they are warming up. That is totally normal. It used to be that you would expect them to rise only a couple psi. But I find mine jumping 4-6 psi between cold (relative - I live in Florida) and warm (in the noon-day sun after a bit of a drive). Yet, they seem to be fine once things have stabilized. I always have my TPMS screen up so, I watch the tire pressures change during all sorts of unusual situations.

Larry Cable

you *might* try changing the settling from summer to winter wheels/tyres and back again ... that's about it... I'd also check your gauge to see its accurate

Jabs1542

I use a Longacre gage and found my TPMS to be within 1 psi under all conditions, cold, hot, and very hot (track).

Try to borrow a good gage from a friend or an auto parts store. If you can consistently prove the TPMS to be way off then go to the dealer.

TPMS saved my butt at Mid Ohio when I picked up a key (yes, a car key that punctured my tire) at speed on the track. This is a good system to have properly calibrated

BradB

+1 I find it very accurate as well. I keep the TPMS MFD in view when I run on the track. It helps me monitor pressures as the temps rise.

StormRune

Another vote for the problem being your gauge, especially since you saw the same discrepancy on your previous car. It would be unlikely for all 4 tire sensors to have the same error of that magnitude if it was the sensors, especially across two cars.

Like Jabs, I also have a LongAcre liquid-filled gauge (0-60 range one that has a valve you use to equalize to the atmosphere for the best possible reading) and have gotten a virtually identical readout between the gauge and all 4 of the cars I've had with TPMS, including after the TPMS batteries aged-out on one of them and was replaced with OEM sensors for a total of 5 sets of comparisons.

Jabs1542

Track Tip: Go into your MFD and disable all the BS screens. I keep the Vehicle Gage's and the TPMS active. That way I can pull the stalk and check back and forth between the two screens while on the straights.

LexVan

My digital tire gauge and TPMS are within 1 PSI of each other.

Thundertub

So here is some trivia about your TPMS system.
The entire TPMS software and hardware system was designed, engineered, and built using the metric system. All of the digital calculations are still being done in metric equivalents and then mathematically rounded up or down to the next closest whole number in PSI.
1.0 BAR is equal to 14.504 PSI. Thus 1/10th of a bar equals 1.4504 psi.
If you watch your TPMS gauge carefully, you will notice you never see 31, 37, 41, 43, 47.
This is because internally, these numbers are being "skipped" because the next multiple of 1/10 of a bar is higher than the next "PSI".

For example, your left front tire reads 36 PSI, and your right tire reads 38 PSI. In reality, they might only be a fraction of a PSI apart but not enough to roll the software to the next 1/10 of a BAR and then displays as the nearest whole number.

I believe that metric displays only read to the 1/10 of a bar - i.e. 2.7, 2.8 etc. That means they are only reading every 1.45 psi difference. Unless you are a track racing person, apparently anything less is unimportant for daily driving.

Scottish Pete

The tire pressure monitoring system (TPMS) compensates for temperature. When my tires are still cool after a few minutes driving to stabilize it will show they are all -0- pounds off and okay. After driving in 100 degree heat for an hour or so on the freeway the tire pressures shown will have risen 4 pounds or so yet the TPMS still shows they are -0- pounds off and okay. Probably uses the outside temperature gauge on the car.

jsaviano

I use a Joe's racing gauge, and it agrees very closely to the TPMS.

StormRune

That's a great analysis! Thanks for posting that.

Good point about the built-in temperature compensation. Higher-end direct TPMS systems like ours often include the temperature sensor within the TPMS device itself. The temperature info gets transmitted along with the pressure. You can find a few mentions of this online, here is a page on the Bridgestone site that mentions it: http://www.bridgestonetire.com/tread...how-tpms-works

I certainly like that feature on our cars since it takes the guessing out of setting the tire pressure using the TPMS delta readout.