Was going to bring the psi to the recommended 42 today and was surprised to see the reading was much lower than what the car says, is there a way to reset now that I put the air in?
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psi reading on my tires is not accurate, car says they are 37-38 psi, I connected my compressor to it and it says 33.5 psi
- Thread starter gottagofast
- Start date
Why do you trust the compressor reading more than the car? I'd try another tire gauge or two before assigning blame.
rpiotro
Active Member
So? That doesn't mean it is accurate. The sensors on the car are not precision devices, but I highly doubt they are off that far. Spend a little money for an accurate gauge. Something like this;
Amazon.com: Astro Pneumatic Tool 3018 3.5" Digital Tire Inflator with Hose : Automotive
A high end professional compressor with a pressure gauge calibrated by an independent third party lab? Or a disposable piece of junk $15 compressor from Wal Mart?
In my experience (2 Teslas, 2 sets of wheels/tires/TPMS sensors, so 16 TPMS sensors total) the Tesla TPMS tire pressure readings are spot-on.
I think it's the compressor nozzle. If you the compressor type that screws in nozzle, I think that's a little bit better. If you have the compressor nozzle that pushes in with a latch, it probably is sensitive to how much you push onto the valve stem before closing the latch. This probably will affect the reading on the sensor.
zoomer0056
Active Member
The car does not give a range 37 to 38 as the thread title suggests. It either says 37 or it says 38. So far only two sources have been used, the car and a compressor. A dedicated PSI reader can also be used. It is doubtful that any reading is 100% accurate and highly likely that 10 readings from 10 devices will show 10 different readings. Unless it's way off as compared to your compressor, use the car reading as the definitive value. Adjust your use of the compressor to get the reading you want from the car. That's what I do. I use the reading of almost 44 on my compressor to get 42 in the car's reading.
Edit: my bad. The title relates to the reading of all four tires, each one either being 37 or 38.
Edit: my bad. The title relates to the reading of all four tires, each one either being 37 or 38.
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TPMS sensors are on the whole consistent and pretty accurate. Within +/- 1PSI at most from a lot of testing I've done.
So as above trust the car's numbers if you don't have a decent gauge or have done some sort of calibration or comparison against a known good guage.
So as above trust the car's numbers if you don't have a decent gauge or have done some sort of calibration or comparison against a known good guage.
EVRider-FL
Active Member
The PSI reading in the car is not real time unless you’re driving. Whatever you’re seeing is from your last drive, so that’s one possible reason for the discrepancy.
fholbert
Active Member
Harbor Freight? Did the compressor cost more than a TPMS sensor?
Four different TPMS sensors conflict with one air compressor. Why do you have confidence in the air compressor?
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Looks like the compressor or car is off by 4 psi, compressor said I put in 40 psi car says the tires are 44, so next time I’ll put in 38
It’s one of those portable ones you can plug into an outlet, I like them for road emergencies I can fill up anywhere I am, $50
That's what I do when topping off with my $15 Wal Mart compressor (I keep one in each car).
Good point - it will show "2 hours ago" or something like that if the sensors are asleep. They do stay awake for a few minutes after you stop; I can often double check my readings through the front window as a fill up each tire.
I've got a $100 (without battery) Milwaukee compressor and it's a good 2-3PSI out most of the time.
The gauge on a compressor is just a guide. You use it to put air in just above the pressure you want and then use a separate quality gauge to set the pressure.
The gauge on a compressor is just a guide. You use it to put air in just above the pressure you want and then use a separate quality gauge to set the pressure.
Since I over filled these tires a little at 44 psi when the recommend is 42 I’m not going to blow a tire going down the interstate or anything am I?
fholbert
Active Member
The sidewalls will list a max load @ max pressure. Probably @ 51PSI cold, so you're fine.
Tire pressures are spec'ed and measured cold (after several hours of rest). Best to measure in the morning, or a cloudy day, They will warm due to friction while driving or sitting in the afternoon sun, with a resulting increase in pressure. Do not bleed off this increase in pressure, or you will be underinflated. 51PSI cold means they are designed to handle more than that when hot.
See:
and:
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