Onboard air compressor inaccurate or tpms?

[peyang]

Wondering if anyone else had issue when using onboard air compressor to pump tires, I set to 50 psi and pumped up all tires, they read +7 to +9 higher onboard, dash says I’m running from 57 to 59psi, seems like a big difference, wondering which system is correct…

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[LeDiable]

I haven't used the onboard compressor, but comparing the TPMS to a digital pressure gauge the TPMS seemed to read high. Been awhile since I compared them though, maybe it was the other way around. I can try again tomorrow and report back what I find.

 

[teartags]

Wondering if anyone else had issue when using onboard air compressor to pump tires, I set to 50 psi and pumped up all tires, they read +7 to +9 higher onboard, dash says I’m running from 57 to 59psi, seems like a big difference, wondering which system is correct…

I can tell you that the "set pressure" on the compressor doesn't work too well on bike tires. Granted it's pretty low pressure (22ish PSI) and it's getting routed through a skinny presta valve, but it can vary easily 5 PSI on my quick trial run. I'm gonna try to dial it in better soon, but I don't have hi hopes.

 

[ohseedee]

I've seen inconsistencies but not as bad as yours. Typically, mine are in the opposite direction as I'll set the compressor to 48, but then the tpms reads ~46. I assume your tpms readings are right after you fill up? When I drive and air heats up I'll see a previous 48 go as high as 52.

I did have a strange tpms issue the other day. Was driving had got a low-pressure alert on one of the wheels. I looked and showed ~47, then after a minute the warning went away.

 

[Oldsmobile_Mike]

Only used it once, but the onboard compressor seemed to be off by 2 lbs. Set it to 48, independent digital gauge and TPMS both reported 50. Imo not a huge difference, but I'd be worried if it was 7-9 off like some of the other folks...

 

[sub]

I have been using a dewalt cordless air compressor on my Rivian's tires. If I set it to 48.5 and press go the TMPS sensors will end up all reading 48.0.

If my TPMS sensors are off, the compressor's sensor is off by pretty much exactly the same amount.

 

[Golfer04]

I have been using a dewalt cordless air compressor on my Rivian's tires. If I set it to 48.5 and press go the TMPS sensors will end up all reading 48.0.

If my TPMS sensors are off, the compressor's sensor is off by pretty much exactly the same amount.

I had a similar issue. Set compressor to 48psi and filled tires. Gage in the cabin says 52. Checked with a digital pressure gage and said 48. Trusting the digital.

 

[Marchin_MTB]

They are both wrong. The TPMS reads low while the compressor is high, both by about 2-3psi. When I asked service about this they told me that it’s a know issue.

 

[SANZC02]

I always use a quality gauge when I check mine.

TPMS is really just a warning system, good to know how it normally reads but I would not rely on the value to be that accurate.

Air compressors can get you close but unless the gauge s at the end where the tire is depending on the temperature of the hose the values will be inconsistent.

 

[UnsungZero_OldTimeAdMan]

Neither are pin-point accurate or grossly inaccurate. Neither are lab grade instruments. Both are adequately accurate for safety. Point? Don’t get OCD over it. They both provide a good enough general purpose guide. If you want though… see this thread for more info.

 

[Foobar]

Make sure you set the target before each tire. I assumed it retained the setting after the first tire and ended up over inflating the remaining three.

 

[NDIrish]

Wondering if anyone else had issue when using onboard air compressor to pump tires, I set to 50 psi and pumped up all tires, they read +7 to +9 higher onboard, dash says I’m running from 57 to 59psi, seems like a big difference, wondering which system is correct…

Compressor for sure is inaccurate... I set 5-7 psi below where I want... TPMS seems to compare to my manual gauges much closer and onboard compressor overshoots and has wide variation

You are not alone

 

[peyang]

Thanks all, good tips & nice to know I’m not the only one

 

[S.Mueller]

I used my onboard compressor for the first time this week and set it to 48psi for each tire. After the compressor shut off it was reading 52-55psi, on the compressor gauge. Ive put in a ticket for it and since I have a mobile service appointment scheduled for 12/13 they’ve added it to be checked then. Will update the findings after that happens.

 

[Tr4ckD4ys]

I set the compressor to 53 psi and my TPMS reads 51 cold, which I believe is off by about -2psi, so my actual cold pressure is probably ~49psi

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