TPMS Accuracy

TPMS Accuracy

I purchased a Martins Industries MHA-100 automatic tire inflator accurate to +/- 0.3 PSI. The cold tires were inflated to 45 PSI, the recommended pressure, but the TPMS indicates 46 PSI on the driver's display, and can show as high as 49 PSI after about a half hour of 60 mph driving on a 50 degree day. Does this sound normal?

Bighorn | March 16, 2019


barrykmd | March 16, 2019

I second the motion from the gentleman from Wyoming.

hammer @OR-US | March 16, 2019

And the motion is carried.

murphyS90D | March 16, 2019

Rule of thumb:

For each 10° F change in ambient temperature the tire pressure will change 1 psi. | March 16, 2019

And when driving fast, the tires heat up too. That's one reason the tire pressure (when filling them) should be measured when cold (i.e. not driven in the last hour or so).

barrykmd | March 16, 2019

Another rule of thumb - as elevation changes, the TPMS becomes inaccurate because it has no external reference. A mile above sea level it reads 3 psi low (if calibration was done at that elevation).

sr.smr | March 16, 2019

Thanks guys!

NKYTA | March 16, 2019

There isn’t really anything to add from response post one, nor what a search on the forums might reveal, or a search on google.

But it is nice that in these trying times, owner outreach still exist with details.

Shall we talk about rivets now? ;-)

kerryglittle | March 24, 2019

@NKYTA Steering bolts might be the new rivets. I don't know where Tesla gets their parts made but how long can it possibly take to get simple bolts made???? Been waiting since last year to get mine checked or replaced. Not to mention air bags.

murphyS90D | March 24, 2019

My steering bolts and air bag were replaced in my garage last Friday by a mobile technician. It took him about an hour and 5 minutes. I never got a notice that either were available, I had to request the appointment.

The steering bolts in my 2013 Ford Fusion Energi were replaced about two years ago for the same reason.

hammer @OR-US | March 24, 2019

@kerry, Steering bolts have available for a long time. Mine were replaced on both my S's last summer. Have you made a service appointment in the last six months?

BarryQ | March 24, 2019


barrykmd | March 24, 2019

kerry - both my steering bolts and airbag were replaced last week.

kerryglittle | March 24, 2019

Hi guys. Living in Canada usually you are at the bottom of the list. I just got a mail about the air bag replacement last month and the bolts many months ago. They said in the mail that they both weren't available but they would contact me when they are. My car is still in winter storage until next month so not in a rush. If they don't contact me by then I will do a follow up.

hammer @OR-US | March 24, 2019

Kerry, they dont notify when the parts are in, they just do the replacement when the car is in for work.

NKYTA | March 24, 2019

Tire pressures usually show up on my 2012 MS after 1/10th of a mile. Elon seems to like that demarcation.

Similar to our 3.

As long as you aren’t Navigating somewhere.

kerryglittle | March 25, 2019

Thanks hammer. I didn't know that. Guess they shouldn't have said that in their mail then. I hate to bug people and assume ( wrongly) that people are doing their job and say they will notify me when parts are in that thats what would take place. The bolts should be fine because my car hasn't ever been in salt or snow. But you never know. | March 25, 2019

@NKYTA - I think that's true of most TPMS systems. The sensors go to low power mode, and only check if the tire is moving every few minutes or so (Not sure of the time). I suspect some car's software (not Tesla), shows the prior reading before the car was turned off as a fake, until a new reading is sent. Sounds like you have a retrofit to the new TPMS if you're seeing pressures - nice!