srb1194

Hello all,

I recently replaced tires and OEM TPMS sensors. Everything works fine but I'm curious how accurate other's sensors are. Mine seem to be off about 3 psi. For what it's worth the last ones were inaccurate also but they were 10 years old. Any thoughts are appreciated.

Steve

MrMoose

That's more than I'd expect. You sure the gauge you're comparing them to is accurate?

You're not at high altitude, are you? Anything over a few thousand feet they'll start to read more and more low, as they can't correct for local pressure variations.

srb1194

No definitely not high altitude but good point. In regards to the gauge I'm using, all I can say is my Ford truck reads exactly the same as my gauge. I always assumed it was correct until I bought this car. Thanks for your input.

Carreralicious

Mine are off by 2 or 3psi too versus my tire gauge. Same with my Benz SUV though too, so I just live with it.

user 729082021

Ohhhhh. I'm in Denver and mine have always read 6 psi low.

krazykarl

My sensors read low here as well, which forces me to run them higher than the recommended level in order to keep the light off.

user 729082021

You can reset the TPMS so the light stays off at lower pressure readings. Don't ask me how. I feel like I did the same thing 3 times and then it finally stayed off.

wjk_glynn

The pressures reported by my HUF TPMS are very close to those measured by my Longacre temperature compensated tire pressure gauge.



Karl.

Wayne Smith

Mine have always been accurate ... early build 2010 C4S and still operating with the original sensors.

srb1194

Now I'm curious which is correct on mine. Too bad there isn't a calibration method or is there?

MrMoose

I could be wrong, but no calibration method I've been able to find, either in the car or by programming the TPMS sensors themselves.

Seems weird to me given the altitude issue: if you live in someplace like Denver the sensors are going to read consistently 2-3 PSI low. Might be due to safety concerns or something, if they got programmed wrong could be a safety issue.

Jim48

I have a 2006 997 C2S and ordered the TPMS as an option (it became standard the next year). First set of sensors lasted 7 years and have had the new ones since then (now 9 years - probably better batteries). They still work pretty well. Regarding the readings, mine are always low until I have driven for a while. Then they register the pressure I put into the tires. If the temperature is high, then, of course, the pressure reading goes up. I am not at a very high altitude (about 800 feet), but when I drive in the local mountains (2-3,000 feet), I don't get any reduced readings. Every once in a while I won't get a reading or will get a warning that the pressure is too low. I first check all he pressure with a gauge, then if the pressure is okay, I do a reset, drive for a while, and it usually begins working properly again. If it didn't work properly, I guess it would mean I need to replace the sensors - not an inexpensive proposition.

srb1194

My pressures rise too once I've driven a little while but I still believe they are lower than actual pressure. I'm using my truck as a reference and they're spot on so I'm inclined to trust my gauge. I have OEM sensors so I know they're genuine. Confused....

Vape NYC

Mine are about 10PSI off. Maybe I have it set wrong - should it be partial load or full load, winter or summer? (I’m using Continental all season tires which are longer made for the rears- please see my other post about this)

MrMoose

So the actual tire pressure will vary about 1.5 PSI for every 10F. As you drive the tires heat up so the pressure will increase.

If you pull up the pressures in the display by pushing the lever on the left up a few times (on the 987.2, at least - I assume the 997.2 is the same?) that tells you the actual pressures currently in the tires. If you pull up the pressures by going into the TPMS submenu (push forward, select TPM, select Info Pressure...this only works when fully stopped) it'll tell you the difference between your current pressure and the programmed spec. This second menu is corrected from the temperature inside the tire to the spec at 68F, which isn't really made clear.

Example: the spec for a tire is 32 PSI. You fill it to 33 PSI in the garage at 68F. The first menu will read "33" and the second menu will read "+1", because it's 1 PSI over spec.

Now you park the car out in the cold overnight. In the morning it's 48F. If you pull up the pressures, the first menu will now read "30" (3 PSI lower, because the pressure dropped due to the 20F lower temperature) but the second menu should still read "+1" because it is temperature corrected. In theory this lets you do things like fill the tires when they're hot (using the values in the second menu, if it says "-1" then just add 1 PSI to whatever it is). In practice I've found it to be too inaccurate to be useful for anything but emergencies.