Chevy Bolt EV Forum banner
21 - 40 of 44 Posts

·
Premium Member
Joined
·
160 Posts
Discussion Starter · #25 ·
Mine are never accurate. Always read low
Are you sure it couldn't be that your tire gauge is high?
I’m not saying the sensors couldn’t be inaccurate, but tests of off-the-shelf tire pressure gauges which I read somewhere show and it’s not uncommon for some of them to be quite a bit off either.

One reason I might be letting the sensors off the hook is it seems unlikely that all four of them would be miscalibrated and showing low. Just a thought.
 

·
Premium Member
Joined
·
160 Posts
Discussion Starter · #26 ·
TPMS sensors have accelerometers in them and only regularly broadcast pressure data (usually once per minute) when the vehicle is moving faster than 15mph. ….

…..So maybe this is your scenario...

You parked your car with 33 PSI in each tire.
You added 5 PSI to each tire...but you didn't drive the car after that.
You check the Chevrolet app later and it still shows 33 PSI in each tire…..
.
That was exactly right. Drove it and the False 33psi reading was replaced by 41.
 

·
Registered
Joined
·
5,547 Posts
One reason I might be letting the sensors off the hook is it seems unlikely that all four of them would be miscalibrated and showing low. Just a thought.
And @Tarrngtn's Bolt is located in an area over a mile above sea level. My Bolt also reads low because I'm at 3,900 feet ASL. Our tire gauges readings are gauge pressure where the tire sensors are absolute but reported as gauge pressure. So the Bolt's readings are off because the programmers used a calibration/offset of the sensors that is based on the atmospheric pressure at sea level.
 

·
Premium Member
Joined
·
160 Posts
Discussion Starter · #28 ·
.
…..Bought a digital gauge finally because every one I had read differently…
Jeff…
How do you know your digital gauge is any more accurate than your other ones?
Are you saying that it's more consistent … for example that it comes up with the same number three times if you times the same tire three times in a row?
 

·
Registered
Joined
·
28 Posts
Recently, with the cold weather , I had to add about five PSI air to each tire to bring them up to the recommended 38 PSI. *

this morning my Cheviot is consistently reporting front tire is down to 33 psi.
But when I check it with two actual real physical tire pressure gauge is it shows to be about 38..As I expected.

So my questions are:
Has anyone else run into anything like this?
Any explanations?
Any solutions?

If it’s a bad sensor, think Chevy will cover it? ( I’m well within my three-year 36,000 mile warranty.)

Alex
* P.S., It strike me as somewhat surprising that although all four tires were down to 33 psi nothing in the Bolt ever popped up to alert me to that AFAIK. I only noticed it when I deliberately change driver information display to show the tires.
On my 2021…. All tires appear to lose air regularly, according to the sensors at least. Never had a car do this. I’m adding air once a month….. about 5 pounds per tire. One tire loses around 8 per month. Never thought about checking and comparing with a gauge. Great tip, I’ll do this next. If it keeps up it’s going to tire shop soon. These are original tires with 13k miles.
 

·
Registered
Joined
·
6,349 Posts
On my 2021…. All tires appear to lose air regularly, according to the sensors at least. Never had a car do this. I’m adding air once a month….. about 5 pounds per tire. One tire loses around 8 per month. Never thought about checking and comparing with a gauge. Great tip, I’ll do this next. If it keeps up it’s going to tire shop soon. These are original tires with 13k miles.
Seems you turned down the $200 nitrogen dealer add-on. 😉
 

·
Registered
Joined
·
4 Posts
Recently, with the cold weather , I had to add about five PSI air to each tire to bring them up to the recommended 38 PSI. *

this morning my Cheviot is consistently reporting front tire is down to 33 psi.
But when I check it with two actual real physical tire pressure gauge is it shows to be about 38..As I expected.

So my questions are:
Has anyone else run into anything like this?
Any explanations?
Any solutions?

If it’s a bad sensor, think Chevy will cover it? ( I’m well within my three-year 36,000 mile warranty.)

Alex
* P.S., It strike me as somewhat surprising that although all four tires were down to 33 psi nothing in the Bolt ever popped up to alert me to that AFAIK. I only noticed it when I deliberately change driver information display to show the tires.
I am having EXACTLY the same problem now, with the exact readings that you have. No explanations nor solutions, looking like you here on the Forum. Thanks for posting!
 

·
Registered
Joined
·
8 Posts
Public service announcement:

Colder temps mean colder air in your tires, that means lowers their pressures! That whole Ideal Gas Law: PV = nRT. Who was paying attention in high school chemistry? Lol. Warning lights should be coming on, please add air to your tires. Recommended psi is normally posted on the inside of the driver’s door. My wife is a chemist for a major tire company and I work for Summit Racing Equipment. All gauges have a tolerance of accuracy. That general rule of a 10 degree swing in temp, yields between 1-2psi change in pressure. Just make sure your tires are aired up correctly to help with improved range and safety of tires.
 

·
Registered
Joined
·
15 Posts
I recently mounted new wheels and winter tires including new TPMS sensors. Activated the sensors per advice here (thanks) and they are reporting pressure. However they are reading 3psi less than my analog pressure gauge; all are 35 (cold) not 38. The OEMs are typically within 1psi of the tire gauge. Kind of annoyed. Any practical solution available?
 

·
Premium Member
Joined
·
2 Posts
I am also at high altitude (Albuquerque 5,000 to 6,500 at my house).
I do not own a Bolt (yet), but have owned several older Porsches and can speak to their TPMS systems with the hopes my observations may help.

Porsches' TPMS systems measure absolute pressure (i.e as if at sea level). As a result, I always add three psi to each tire to account for the reduced ambient air pressure here in Denver. Also -- Porsche instructs owners to add air when the tires are cold, using an ambient temperature of 68F. If it is colder than 68F in my garage when I add air, I always reduce the air I put in each tire by one (1) psi for every ten degrees of temperature drop. That lets me achieve the desired pressures when the tire temps come back up to 68 degrees. (And increase the pressure if it is warmer than 68F in the morning when I add air in my garage.)

When I get into the car in the morning in the garage, the temp in my garage in the winter is usually in the 40's. As a result, the TPMS system always reports pressures that are under those that are desired at 68F -- but they come back up after driving the car a while.

Another thing I learned is that the recommendation on the inside of my driver's door is for a fully-loaded vehicle with four adults. My Owner's Manual has two pages of recommendations however, which take into account wheel size; tire type (i.e. A/S, summer, winter, etc) and the number of passengers. If I was to solely use the recommendation on the inside of the driver's door, I would experience uneven wear. Most of the wear would be in the center of the tires due to over-inflation.
 

·
Registered
Joined
·
2 Posts
No mystery here - any gas's pressure is directly proportional to temperature (remember PV=nRT from HS physics?). So P=nRT/V. Tire volume can change but it turns out that for small pressure difference it doesn't make much of a contribution The temperature has to be measured in degrees (C or F is irrelevant, just be consistent) from absolute 0. Freezing 32F which is 273.15 above absolute 0, so 20F is 261 farenheit degrees above abs zero and 72 degrees is 313 farenheit degrees above abs zero. If we use 313 as the baseline temperature, the proportion 261/313 = .83 show that the pressure at 20F is only 83% of the pressure at 72F. So if your tire pressure at 72F is 38 psi it will only be .83 x 38 = 31.5 psi at 20F. Don't waste your time getting new sensors!
 

·
Registered
Joined
·
24 Posts
Same experience here.
Since I bought the car, the TPMS has read 4-5 pounds lower than actual pressure as measured by a calibrated tire gauge. I had to buy a new set of tires, with no effect on the readings either way. All TPMS readings while car is driving and has been on the road for a while, so accelerometer not a factor. I simply make a mental adjustment and add air when the tires are a few pounds low as measured by my accurate gauge. The TPMS readings are only annoying when MyChevrolet tells me my tires are low when they aren't in fact low at all. I once asked in this forum if it was possible for the TPMS system to be recalibrated to give correct pressures, and the answer was no.
 
21 - 40 of 44 Posts
Top