TPMS Acting Up

[Resist]

This morning I got a low tire pressure icon for the left front tire. Looking at the pressures on the display it showed all the tires were 36psi with the left front tire number in orange and the others white. As I drove around for several miles nothing changed. When I turned off the car and drove again for several more miles the low tire pressure icon was still on but now all the tire pressure numbers were showing in orange. After a bit the front left tire pressure dropped to 35psi and the others stayed at 36 but the numbers changed to white. The car running the FSD beta and is on firmware 2022.20.18, the next firmware is 2022.20.19 but I can't install it until later today.

I'll see what happens with this new update, hopefully it will straighten it all out. Just a very weird thing that I've never experienced before.

 

[tm1v2]

What size tires are you running? And on what size wheels? (Asking the latter just in case you're using a very stretched or squished fitment.)

In my opinion - and this is an opinion, not a hard fact! - if you're running stock-size 235-245mm width tires then 36psi cold or near-cold is too low. Now I also feel the factory 42 psi cold recommendation is slightly too high, at least with my current 245/45R18 300TW tires, but 36psi cold is too far in the other direction. I've been liking 39psi cold lately.

To me it doesn't sound like you have any leaks but keep monitoring your pressures of course. I'm guessing your tires were filled to something 39-41psi cold when it was warmer out, which is good, and now with the cold, dense fall air that's become 36psi. That's expected, even California has enough seasonal temperature variation that I would expect to top off tires for the winter, and then air them out again for summer, to maintain a consistent pressure range through the year.

As for why the car was calling out 1 specific tire first, then later all 4, I wouldn't worry about that. Just get your pressures right and the car will be fine.

 

[tm1v2]

Also, if you are running 20" wheels with correspondingly short tire sidewalls, like the stock M3P 235/35R20 size, then I highly recommend sticking with the Tesla recommended 42psi cold. 235/35 or even 245/35 is very little sidewall, impacts can reach the rim easily anyways, don't make it worse with lower pressure.

My 39psi cold preference is with 18" wheels and 245/45R18 tires as mentioned. I'd probably be comfortable running 39-40 psi cold on 19" wheels too (assuming a similar outer tire diameter e.g. 245/40R19 on 19x8.5"), though I have not used 19" wheels on this car.

 

[Resist]

Sorry, I forgot to say that I have the 18" tires and completely forgot that the psi was supposed to be 42, of which I normally would run them higher around 50psi. It was very cold this morning (high 30's), when I drove the car after not driving it for a couple weeks and forgot about routinely checking the tire pressures. But all is good now, thanks for the responses.

 

[derotam]

50psi huh, haha. I thought about running that high but I keep mine at 45 cold and they usually go up to 50psi after they warm up.

 

[Resist]

Even though the sidewalls on my 18" tires say 50psi is the max pressure, I know that the actual burst pressure is way higher, so even on hot day they will be fine. So I just right now filled them all up to 50psi cold. I have another vehicle a 2015 Jeep Wrangler that I've had since the end of 2014 and have always filled the tires to 50psi to help with mileage, because it sucks in a Jeep. Never had an issue, even when I took a cross country trip once. I only did this after researching tire burst pressures and was impressed with the safety margins. I also had a 2001 Honda Insight years ago and kept its small tires at 50psi too with no issues. Now granted, you can't overload a vehicle if you run 50psi in the tires and I never do but if I did then I'd lower the pressures. The one trade off is a rougher ride, but I don't mind that because it helps me feel the road.

 

[android04]

Not much weird about the behavior. The TPMS low pressure warning comes on around 37 PSI (looks like it's 36 PSI for you, and can vary depending on your elevation). As for all 4 tires reading the same pressure but showing different colors, that's due to rounding the pressure displayed to you. Some of the pressures might be rounded up and some down from the warning pressure, which might be fractional as well.

 

[father_of_6]

Right, so if the alarm goes off at 35.7 PSI, your tires were dancing around that number. As the air inside the tire heats, it expands and increases pressure or vice-versa.

I agree it all seems normal.

 

[VT_EE]

You can reset the "normal" tire pressure in the service menu. If you have never done this, then the alarm is because your pressure is too low. I had the same symptoms you are describing. I like to ride at 40psi, which means that it would alarm on colder days. The reset TPMS feature resolved my issue.

 

[Resist]

Do people not read all of the thread before posting? Because I figured out the issue at post #4, yet I continued to get responses about it days afterwards.

 

[father_of_6]

Do people not read all of the thread before posting? Because I figured out the issue at post #4, yet I continued to get responses about it days afterwards.

You yourself posted at #6, didn't you read that you solved it at #4 before posting?

It's a dialog. You don't get to tell everyone to shut up because you believe the conversation is over.

Although you say you "figured out the issue", @android04 is the one who described why you experienced the seemingly inconsistent reporting.