Onboard air compressor inaccurate or tpms?

[UnsungZero_OldTimeAdMan]

The key is consistency, i.e. go by the same tool/gauge as much as you can. Too many variables involved to influence measurement results. So reduce inconsistency by sticking with 1 constant. A few psi difference might irk your OCD tendencies, if you have it, but not going to make much difference in normal driving. Even while driving or parked (with partial exposure to sunlight) you will see the same or worse psi delta at each tire. In general, regardless of what car it is, always good to keep a good quality gauge, with release valve, so you have a consistent way to measure, verify or fine tune pressures to a ballpark equilibrium.

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[cwintermeyer]

I recently tried my R1S compressor for the first time. I used it with a MORRFlate quad hose kit to air up the 20" Pirellis after off-roading in Moab. When the compressor shut off at a 50 psi target the MORRFlate digital gauge read 53 psi. When I got back on the road the first TPMS reading was 50 psi for all four tires.

 

[CharonPDX]

TPMS reads a little high but has high accuracy - it's reliably 1-2 PSI high all around; but the compressor is *MASSIVELY* inaccurate/variable. I set it to 50 PSI, inflated all four tires after airing down for some sand driving, and once TPMS re-calibrated, my four tires were between 45 and 55 PSI.

 

[WilcoFan]

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 had the same issue once Chicago got cold. TPMS said my tires were at 40 and needed to be increased to 48 psi. I went to the compressor and targeted 48 and nothing happened. Then realized that the compressor was reading them to be at 48 psi already. Called Rivian and they said to check with a 3rd instrument, and that showed that the TPMS was the correct one. I had a service appointment set up already for another minor issue and so added that onto he ticket.

The service center said this is a common problem. They fixed the compressor and now it works correctly and agrees with the TPMS.

 

[Riv_Ian]

My air compressor used to be dead on; now it’s 7-9 psi high. I measure with a digital air pressure gauge and deflate to get to 48 psi. TPMS matches digital gauge closely.

 

[Singletracker]

My TPMS typically runs about 2 lbs. below what my digital gauge shows. Don’t know about the compressor, but that is not something I would ever depend on for accurate readings. It will pump air and get you close, but I don’t think it’s reasonable to expect much more. For accurate readings, check tire pressure with a proper digital gauge.

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