Tire Pressure Question

slasher016

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#1
So yesterday my TPMS went off telling me my tire pressures were low. Interestingly as I drove it varied between one and three tires that needed pressure. Perfectly normal, the temperature was in the 90s for weeks and dropped into the 60s the past two or three days. No problem. They were reading anywhere between 35-37 on the in screen card. I added pressure to all four tires bringing them all to around 41 on my (probably not very accurate) gauge.

When I get back in my car this morning and drive a bit, all four say they're 38 -- I wanted them 39 so I still need to put a little air in them, but that's not the issue. Even though all four are reading the same the front passenger side tire is still throwing a low tire pressure warning. I assume that even though they all read 38 they're actually fractionally different which is all fine and everything, but the warnings turned off yesterday (after I had driven awhile) once they all hit 37. Today at 38 the one is still going off. Anyone experience this or have any thoughts?
 

tencate

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#2
Mine went off the other day too, the cold morning temps showed one tire at 37 or 38 psi, I forget now. I added a bit of air to them all and all has been well now.
 

slasher016

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#3
Mine went off the other day too, the cold morning temps showed one tire at 37 or 38 psi, I forget now. I added a bit of air to them all and all has been well now.
Ok sounds like maybe I'm still just a bit below the threshold. Hopefully adding another lb of pressure on each will kick it off. Still odd that sometimes it reports an issue at 38 and sometimes it doesn't even at 37.
 

Ed Woodrick

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#4
So yesterday my TPMS went off telling me my tire pressures were low. Interestingly as I drove it varied between one and three tires that needed pressure. Perfectly normal, the temperature was in the 90s for weeks and dropped into the 60s the past two or three days. No problem. They were reading anywhere between 35-37 on the in screen card. I added pressure to all four tires bringing them all to around 41 on my (probably not very accurate) gauge.

When I get back in my car this morning and drive a bit, all four say they're 38 -- I wanted them 39 so I still need to put a little air in them, but that's not the issue. Even though all four are reading the same the front passenger side tire is still throwing a low tire pressure warning. I assume that even though they all read 38 they're actually fractionally different which is all fine and everything, but the warnings turned off yesterday (after I had driven awhile) once they all hit 37. Today at 38 the one is still going off. Anyone experience this or have any thoughts?
I hear two impacting issues in your story
  1. (after I had driven awhile) is not the cold pressure
  2. all four say they're 38 -- I wanted them 39 - are both less than the recommended 45 psi., if you stay low, you risk setting off the alarms.
 

John

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#5
Once the tire pressure warning is triggered, you have to drive your car for over 10 minutes faster than 15 mph for it to clear after you fix the pressure (or the tire warms up).
 

slasher016

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#6
I hear two impacting issues in your story
  1. (after I had driven awhile) is not the cold pressure
  2. all four say they're 38 -- I wanted them 39 - are both less than the recommended 45 psi., if you stay low, you risk setting off the alarms.
Actually Musk has said that 39 is what you should run if you want better ride quality, and that's also what the service center had them set at originally.

EDIT: Here's the tweet:
"
 

slasher016

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#7
Once the tire pressure warning is triggered, you have to drive your car for over 10 minutes faster than 15 mph for it to clear after you fix the pressure (or the tire warms up).
Yeah... I think in the end that was the problem. My short commute to work (~3 miles) just didn't trigger it to turn off. When I took it out to lunch and back it went off and stayed off. So I'll know for next time.
 

Sumiguchi

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#9
I've never had a car with tire pressure sensors before and the cold snap and general fluctuation of temperature is killing me. It really sucks to have to put air in the tires when it's -30C!

Does using Nitrogen make a difference?
 

TheMagician

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#10
I've never had a car with tire pressure sensors before and the cold snap and general fluctuation of temperature is killing me. It really sucks to have to put air in the tires when it's -30C!

Does using Nitrogen make a difference?
Never seen any tests conducted at that low a temp (why do you live there :) ) but in general, no, nitrogen doesn’t have any effect on pressure increase/decrease. There might be some benefit on how long the tire holds a given pressure but even that claim is somewhat dubious. Easy enough to prove it to yourself though, put nitrogen in 2 tires (one front, one rear) and leave good old air in the other two.

With the screen you can monitor real time pressures (and please let me know if I’m wrong). Like I used to say at work, “I show up every day and find out I’m not as smart as I thought I was the day before”.
 
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#12
I’m running lower pressure now, had to replace rears at around 20k miles and wear pattern showed quite overinflated. Also hadn’t rotated with front.
 

TheMagician

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#13
I’m running lower pressure now, had to replace rears at around 20k miles and wear pattern showed quite overinflated. Also hadn’t rotated with front.
You said a lot while saying so little :). What pressure were you running in the rears when they showed over inflation and what are you running now? Most people run the same pressure in all 4 tires. You’re not the first to report replacing tires at 20k. Would be helpful if we knew rwd vs awd. Some people claim rotating is overrated but I’m still a big believer, especially with rwd. I had noticeable wear at 6K with rwd. Car is just too much fun.
 
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#14
RWD
Not sure what pressure exactly, but had to press up when it got colder to stay above 40psi the tpms wants. Don’t remember seeing above 45 psi ever.

Trying to stick around 38psi when tires are warm now, and monitor more often. Almost 1k miles on new tires so too soon to tell.

May get worse efficiency at these pressures, but there’s also cost with needing 1300$ tire change early. I’d like to do some efficiency tests with tire pressure sometime. Even double energy use would not be worth going through tires twice as fast.
 
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#16
why didn't you rotate them in that 20k?
Maintenance?? Who needs maintenance!

Was planning to just replace rear separately from front. Fronts were also bad due to bad alignment after playing around with suspension and not realigning.

From now on get free rotation from the shop that replaced the tires :)
 

Swoop

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#17
I'm unsure about the Model 3, but in our other cars, the tire pressure monitor system triggered from a set differential between the tires, not a pre-set min pressure. So if they were all at 30psi at the same time, they wouldn't go off. If one was 25psi and the others were 35psi, they would trigger a low pressure warning.
 

TheMagician

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#18
RWD
Not sure what pressure exactly, but had to press up when it got colder to stay above 40psi the tpms wants. Don’t remember seeing above 45 psi ever.

Trying to stick around 38psi when tires are warm now, and monitor more often. Almost 1k miles on new tires so too soon to tell.

May get worse efficiency at these pressures, but there’s also cost with needing 1300$ tire change early. I’d like to do some efficiency tests with tire pressure sometime. Even double energy use would not be worth going through tires twice as fast.

Not going to tell you what to do but sounds like it was more likely alignment/lack of rotation issues than overinflation. If you’re at 38 warm, that’s roughly 35 cold which, for this car, is a little low. I’d at least run 40 cold on all 4 corners. We have people here that are running 50 psi! I run 42 cold and, with almost 10K miles, my tires are wearing great (I rotated at 6500). I have 19” Continentials and at this rate, should get 25-30K miles.
 

slasher016

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#19
I'm unsure about the Model 3, but in our other cars, the tire pressure monitor system triggered from a set differential between the tires, not a pre-set min pressure. So if they were all at 30psi at the same time, they wouldn't go off. If one was 25psi and the others were 35psi, they would trigger a low pressure warning.
That's not the way the Tesla one works. I've had mine all the same and it went off.