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Discussion Starter #1
I bought my Bolt back in mid-December 2017. I had never checked the tire pressure, other than glancing at it on the car's display, which reads it from the built-in tire gauges in each wheel. I was giving my baby Bolt a bath a couple of days ago, and I figured it would be a good idea to check the tire pressure with a decent gauge. All four tires were overinflated: about 42 psi, versus the door sticker's recommended pressure of 38 psi. So I dropped the pressure to 38 psi. Don't trust your car's TPMS (tire pressure monitoring system). I'm hoping the reduced pressure will help the braking and cornering, but it will also likely reduce my mileage slightly.
 

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I bought my Bolt back in mid-December 2017. I had never checked the tire pressure, other than glancing at it on the car's display, which reads it from the built-in tire gauges in each wheel. I was giving my baby Bolt a bath a couple of days ago, and I figured it would be a good idea to check the tire pressure with a decent gauge. All four tires were overinflated: about 42 psi, versus the door sticker's recommended pressure of 38 psi. So I dropped the pressure to 38 psi. Don't trust your car's TPMS (tire pressure monitoring system). I'm hoping the reduced pressure will help the braking and cornering, but it will also likely reduce my mileage slightly.
Ours were at 38 psi when we got it. Have been set to 40 or higher cold ever sense.
 

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If you had driven the car within a couple hours of checking the pressure, then they were filled correctly and now your tires are under-inflated. Tire pressure is to be read cold, meaning the car hasn't been in the sun, and hasn't been driven in several hours.

42 PSI isn't over-inflated regardless. I'd probably run 45 PSI if I had the Bolt unless the harsh ride finally got to me.
 

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If you had driven the car within a couple hours of checking the pressure, then they were filled correctly and now your tires are under-inflated. Tire pressure is to be read cold, meaning the car hasn't been in the sun, and hasn't been driven in several hours.

42 PSI isn't over-inflated regardless. I'd probably run 45 PSI if I had the Bolt unless the harsh ride finally got to me.
Yes, to checking cold after sitting overnight.

No, any two tire gauges and the TPMS will usually result in three different readings. It's difficult to get hold a gauge on the stem exactly the same way twice and without releasing any air so doing.

Yes, 42 PSI is 10.5% over-inflated in relation to the 38 PSI recommended.

No, 42 PSI is not dangerous or hazardous to the tire; only to the passenger's spinal columns.

jack vines
 

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Discussion Starter #5
Yes, I checked the tires cold: the car had not been driven in over 12 hours. Air temperature was in the mid-70s F: unseasonably warm here in California.
 

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Yes, I checked the tires cold: the car had not been driven in over 12 hours. Air temperature was in the mid-70s F: unseasonably warm here in California.
Every 10*F variation in air temp is worth roughly 1 psi (depending on size of tire and other factors). So if the outside temps were 75*F when you took the measurements, and normal temps are 55*F, you're going to drop 2psi when temps return to "normal".

Within a reasonable range, it's just a trade off between characteristics such as comfort/range/traction/wear life.
 

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My TPMS readings are within 1 PSI of the readings I get from my Meiser tire gauge, and all four TPMS readings are within 1 PSI of one another.

If you’re getting readings that are off by 4 PSI you either have a bad tire pressure gauge or four bad TPMS sensors.

I would suspect it’s the gauge.
 

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Discussion Starter #8
It may also be related to the calibration of the sensors. In any case, a good tire gauge should be the most trustworthy.
 

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My TPMS readings are within 1 PSI of the readings I get from my Meiser tire gauge, and all four TPMS readings are within 1 PSI of one another.

If you’re getting readings that are off by 4 PSI you either have a bad tire pressure gauge or four bad TPMS sensors.

I would suspect it’s the gauge.
Agree. I've only had a few cars with TPMS, but they've all been more accurate than the average tire gauge and the average tire gauge user.

Now, if someone would just solve the problem of why the sync keeps getting lost.

jack vines
 

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If the car is in the sun and it's hitting the tires on one side or the other, you readings are junk.
I also think the gauge is junk and the TPMS system is accurate. Comparing the TPMS to a gauge
is useless. Pick one and use it. I trust my TPMS system 100% and believe it to be more accurate
than 99% of China made junk gauges. YMMV!
 

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If you all dont want to spend money on a decent water filled gauge, they are worth it. I have two. Dans Garage from Amazon, great made in america gauge, I also have a QuickCar water filled. Both are accurate and calibrated.

Now, if you really dont want to spend money, just go buy a cheap pencil gauge. Those will most likely be much more accurate than any cheap digital or analog junk gauge.
 
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