Need advices: PSI is all over the place on first day of snow in my area.

[ThisIsMask]

So today is first snow day in my area and dashboard prompts my front left tire was 37 while all other 3 are 38. I did a quick stop at gas station to pump the front left tire to be consistent with others. It was a painful experience to match PSI so it stopped at 39 for front left tire (rest are 38).

Later in the day, the other tires are yelling (see attachment).

What is your recommendation how to match tire PSI? And does it mean owner needs to adjust PSI when seasons change?

Mine is MX 2020 LRP, 22" Onyx Wheel. Thanks much

 

[Les236]

Yes, you should have to change the pressure from season to season. I am in Northern MA and when the temp first fell below freezing I received a warning. I always use a pump with a gauge and pressurize them all to the same level. If I am not at home, I just make sure to use the same tool to fill each on, and always while cold.

That said, my MX has 20" wheels and my door decal says to fill them to 45 PSI, and when they get below 40 psi I think the warning comes on. are you sure you are filling them to the correct PSI?

On a recent road trip after some time on the highway mine had all increased close to 50PSI but all were still within 1 PSI of each other.

 

[brkaus]

Fill all to same amount first thing in the morning (minimizing drive distance/ speed on the way) using a guage.

 

[scottf200]

So today is first snow day in my area and dashboard prompts my front left tire was 37 while all other 3 are 38. I did a quick stop at gas station to pump the front left tire to be consistent with others. It was a painful experience to match PSI so it stopped at 39 for front left tire (rest are 38).

Later in the day, the other tires are yelling (see attachment).

What is your recommendation how to match tire PSI? And does it mean owner needs to adjust PSI when seasons change?

Mine is MX 2020 LRP, 22" Onyx Wheel. Thanks much

This is oddly a really good YT video on the subject. I was surprised I learn a thing or two from it.

How to put air in tires​

 

[mxnym]

You should check the tire and loading information sticker in your door jamb. I believe mine says 42 PSI, but someone else has indicated theirs says 45 PSI. The manufacturer recommendation varies depending on many factors, so that sticker is the place to look unless you're running an aftermarket setup that necessitates deviating from there. Note that sticker indictaes what the pressure should be when the tires are cold (not winter cold, but unwarmed from driving, since heat generated when driving can temporarily increase the pressure).

 

[tbart75]

This thing is great for tire pressure adjustments and to ensure all 4 are set at the same amount. The pump turns off when you hit the set pressure. Slower than most air pumps but super handy.

https://www.amazon.com/dp/B094DMH7ZM?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[EbS-P]

The X is heavy I run 48psi summer 45 winter. Temperature makes a big difference in tire pressure. I try to measure in the morning before I drive (very far). 1-2 psi variation based on the morning temps is probably to be expected.

 

[ThisIsMask]

Thanks folks. All good info, here is the tricky part I encountered last night when trying get this PSI balanced.

Sticker on the door suggests 42 PSI when cold but per guidelines I researched (and even at pump station recommendation) if tires are hot, +4 PSI. So, I decided to top the tires to 45 PSI, because I just got off the freeway after around 12 miles driving with expectation these should go down a bit when cold in the morning. However, this morning they stay the same at 45 PSI in garage. So, I think when I thought the tires are hot, they are not.

Question would be how would you determine if tires are hot or not when pumping? (I know it's nitpick but maybe interesting to discuss)

 

[brkaus]

I’ve heard it’s about 30-45 min of highway driving to get to steady state temp.

 

[scottf200]

However, this morning they stay the same at 45 PSI in garage. So, I think when I thought the tires are hot, they are not.

To be extra clear you are actually driving it a minute and not just checking the PSIs in the morning right?
You need to drive the car a minute for the TPMS sensors to be measured. They "sleep" when they are not moving. Some cars show -- for the PSI and some show the *last* PSI read (ie. last time it was drove the night before or whatever).

 

[ngng]

So today is first snow day in my area and dashboard prompts my front left tire was 37 while all other 3 are 38. I did a quick stop at gas station to pump the front left tire to be consistent with others. It was a painful experience to match PSI so it stopped at 39 for front left tire (rest are 38).

Later in the day, the other tires are yelling (see attachment).

What is your recommendation how to match tire PSI? And does it mean owner needs to adjust PSI when seasons change?

Mine is MX 2020 LRP, 22" Onyx Wheel. Thanks much

1psi per 10 degrees F is the rule of thumb. This usually means you'll need to make monthly changes. If you're adding air after you've been driving more than a few miles keep in mind your tires will be 2-3PSI higher.

 

[ThisIsMask]

To be extra clear you are actually driving it a minute and not just checking the PSIs in the morning right?
You need to drive the car a minute for the TPMS sensors to be measured. They "sleep" when they are not moving. Some cars show -- for the PSI and some show the *last* PSI read (ie. last time it was drove the night before or whatever).

That is correct, PSI only shows up after driving out of the driveway. I removed that details as I think it shouldn't impact temperature much yet.

 

[ngng]

That is correct, PSI only shows up after driving out of the driveway. I removed that details as I think it shouldn't impact temperature much yet.

Also remember that the TPMS is generally accurate but they can be off +/- a few PSI. You'd have to look up the tech sheet for the actual sensor. Their primary use is to detect a leak or drastically low tire pressure. If you really want to know what your tire pressure is you need to purchase a tire gauge. Even a cheapo one is good enough for this.,

 

[DCGOO]

1psi per 10 degrees F is the rule of thumb. This usually means you'll need to make monthly changes. If you're adding air after you've been driving more than a few miles keep in mind your tires will be 2-3PSI higher.

Ambient temperature is the most impactful factor. I've found that after driving 80 mph for hours had little impact on the tire pressure. But if the outside temp at 70ºF drops to 30ºF, it can drop your tire pressure 5 lb or more. It drives me nuts when Tesla reduces the pressure if the car is in for service in the winter. Because it is 70º inside the Service Center. Even if I tell them "Don't reduce the air in my tires," It is often ignored.

 

[ngng]

Ambient temperature is the most impactful factor. I've found that after driving 80 mph for hours had little impact on the tire pressure. But if the outside temp at 70ºF drops to 30ºF, it can drop your tire pressure 5 lb or more. It drives me nuts when Tesla reduces the pressure if the car is in for service in the winter. Because it is 70º inside the Service Center. Even if I tell them "Don't reduce the air in my tires," It is often ignored.

Agreed. If you are targeting a mid-range PSI like mid-40s even if you're a little high you can bleed the tires down later. My biggest pet peeve is when I tell dealers NOT to wash my car and then they do me a favor and take it through their automatic car wash