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Kind of dumb question - leaving car sitting and tires deflate ...

jonquiljo

Supporting Member
Sep 26, 2019
1,062
496
SF Bay Area - Marin
I am high-risk for COVID, so my life is a bit incarcerated these days. I barely get out of the house to do anything and my Model 3 sits on a charge more time than not. But this isn't about me.

I noticed when I was driving (in San Francisco) the other day (unique occurrence) that my car was feeling kind of "mushy." I called up tire pressure on the screen and saw that the tire pressures were down in the 37-38 psi range - and they had been 44-45 psi 6 months ago. I do get out to drive, but not often and not far. It hasn't been too cold here and certainly not on the day I was driving.

All the tires had deflated. I checked them with a good tire gauge (warm and cold) -- and the TPMS readings were correct. I guess I've never had a car sit barely used this long to see this occur. Is this normal and to be expected?

I used a tire pump and brought them back to 44 psi (warm). They seem to hold the pressure fine. Thoughts? Thanks.
 

jeremymc7

Active Member
Feb 3, 2013
1,296
577
U.S.
As above normal.

I’m actually in same state as you, literally and figuratively.

At a minimum move the car forward or back a couple feet once every week or two. You ideally don’t want the car sitting for months with the tires in the same spot. Best yet but the heater and heated seats on put on a favorite song and go for a 5 min drive.

Good for both the car AND you to get out of the house.
 

KenC

Active Member
Sep 4, 2018
3,488
3,174
Maine
1pound lost a month, should be normal. The sportier, and lower profile your tires, the more you should move them so they don’t flat spot.
 
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Uncle Paul

Well-Known Member
Nov 1, 2013
6,249
6,762
Canyon Lake,CA
totally normal. Good that you are keeping an eye on it.
Pumping them back up was exactly the right thing to do.
Mechanical items do not like to sit idle.
Good to drive it from time to time. Kind of an exercise program for your car.
 

freeAgent

Member
Oct 29, 2020
127
102
SoCal
May help to have 100% nitrogen in the tires. That was the rage 15 years ago - big marketing push with car dealers.

I think that has been debunked. Regular air is mostly nitrogen already (almost 80%) and most of the rest is Oxygen. Oxygen molecules are slightly smaller than nitrogen, but I don't think it's a big enough difference to have a significant impact on the rate at which they can escape a tire.
 

DopeGhoti

Active Member
Aug 28, 2019
1,223
1,376
Phoenix, AZ
You will generally already have roughly 80% diatomic Nitrogen in your car's tires. Going out of your way to inflate the tires with pure diatomic Nitrogen is not worth your time Even if diatomic Oxygen (most of the other appx. 20%) had a significantly different rate of thermal expansion, it would not be signigificant enough to warrant the time and effort to purify the gas mix in your tires. It's much simpler to just check the tire pressure monthly (or indeed more frequently using the MFD's display of tire pressure readings) and top-off as needed.

Note that the Model 3 suggest 42 PSI but this is a cold air pressure- if you're driving somewhere to get the tire pressure checked and filled you'll want to go a bit higher.
 

jonquiljo

Supporting Member
Sep 26, 2019
1,062
496
SF Bay Area - Marin
As above normal.

I’m actually in same state as you, literally and figuratively.

At a minimum move the car forward or back a couple feet once every week or two. You ideally don’t want the car sitting for months with the tires in the same spot. Best yet but the heater and heated seats on put on a favorite song and go for a 5 min drive.

Good for both the car AND you to get out of the house.

Thanks. Sorry you have a similar “problem” to mine.

Anyway, I do get out weekly - sometimes 2 or 3 times a week. It just tends to be for short distances (2-3 miles each). That’s why I was so surprised to see tire pressure drop so much - especially on 18” tires.

I’m assuming the weight of the car makes the problem worse - a smaller car that weighs 4000 lbs is not typical.

Well thanks everyone, I will keep an eye on it more closely. I do know from this that the TPMS sensors are pretty accurate.

Funny, my connecting my “Tesla” portable air pump to my single lighter socket, I seem to have blown the circuit for it. Nothing will work when plugged into the console. I had to finish the job by plugging into another car. Is there a fuse or breaker for the lighter socket in the console? Thanks.
 

holmgang

Active Member
Sep 9, 2019
1,287
1,290
eu
It's not only the fact that ambient temperature is lower, but if you measured early into a drive vs deeper into a drive with much larger loads on the tires that could account for a few PSI as well
 

EmOne

Member
Mar 28, 2020
214
154
Chicago
Thanks. Sorry you have a similar “problem” to mine.

Anyway, I do get out weekly - sometimes 2 or 3 times a week. It just tends to be for short distances (2-3 miles each). That’s why I was so surprised to see tire pressure drop so much - especially on 18” tires.

I’m assuming the weight of the car makes the problem worse - a smaller car that weighs 4000 lbs is not typical.

Well thanks everyone, I will keep an eye on it more closely. I do know from this that the TPMS sensors are pretty accurate.

Funny, my connecting my “Tesla” portable air pump to my single lighter socket, I seem to have blown the circuit for it. Nothing will work when plugged into the console. I had to finish the job by plugging into another car. Is there a fuse or breaker for the lighter socket in the console? Thanks.
Weak physics here. Weight of car has nothing to do with it at a given pressure as a first order effect; due to greater curvature/stretch of the tire with heavier weight, might have second order effect on rate of leakage. Tire size not clearly a big player, though with larger surface area, 18" tire would have more surface area and leak faster all other things being equal (they aren't, of course!). Driving certainly would not slow the rate, just prevents the aforementioned flat spotting. Probably slightly increase the rate due to pumping effect leading to transitory higher pressures...Bottom line, your experience normal, you just looked less often!
 

qingshan

18 lr rwd fsd
Apr 19, 2020
276
126
Pomona Valley
1pound lost a month, should be normal. The sportier, and lower profile your tires, the more you should move them so they don’t flat spot.

The temperature when he noticed it also is an issue. I was driving last winter and my car, not the Tesla, alerted me - just a temp v pressure thing. Was it some guy named after hot water? ;)
 

jonquiljo

Supporting Member
Sep 26, 2019
1,062
496
SF Bay Area - Marin
Weak physics here. Weight of car has nothing to do with it at a given pressure as a first order effect; due to greater curvature/stretch of the tire with heavier weight, might have second order effect on rate of leakage. Tire size not clearly a big player, though with larger surface area, 18" tire would have more surface area and leak faster all other things being equal (they aren't, of course!). Driving certainly would not slow the rate, just prevents the aforementioned flat spotting. Probably slightly increase the rate due to pumping effect leading to transitory higher pressures...Bottom line, your experience normal, you just looked less often!
Yes ... I guess I am used to having a car serviced 2-3 times a year - even new. My Model 3 is coming up on a year old and never been to a shop. TPMS is helpful when you have a problem. I do wonder, however, why the temp dropped from 44-5 to 37-8 and I got no TPMS alerts.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,184
9,041
Riverside Co. CA
Yes ... I guess I am used to having a car serviced 2-3 times a year - even new. My Model 3 is coming up on a year old and never been to a shop. TPMS is helpful when you have a problem. I do wonder, however, why the temp dropped from 44-5 to 37-8 and I got no TPMS alerts.

Pretty much every winter (even in CA) if you havent put air in your tires by then, you would need to. If you had your cars serviced a couple times a year for various things, one thing a car dealer will always do is check the air in your tires. That could be why you never really noticed it before.. assuming you drove cars with built in TPMS before which I believe you mentioned you did.

Not trying to pile on by any stretch, just mentioning why you might not have noticed it previously. Note, if you ever take your car to a tesla service center, they also will fill the tires every time they check the car for something.... even installing a spoiler, or two (or 4).

Have personal experience with that one.
 
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animorph

Active Member
Apr 1, 2016
2,133
1,529
Scottsdale, AZ
As has been said, 6 months and a temperature drop will do it every time.

My experience has been that our X, which can sit unused for long periods, loses tire pressure more slowly than our 3 which is our daily driver. So I think if you had been driving, the pressure drop would have been worse.
 

Nickage87

Member
Nov 28, 2019
113
33
USA
I added air once in my lexus in 5 years. Tesla is one year old and I got low pressure alert on the screen. I think it is because tires are lower and hold much more pressure, meaning more dense air will be affected by temperature alot.
 

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