Some tire shops have a calibrated gauge that you can use to verify the accuracy of your own gauge. One of our local Les Schwab tire stores has such a gauge (along with dated calibration sticker) and, if asked really nice, will let you check your gauge. That said, I bought the same gauge that Gaijin mentions above, and it was within .5 PSI (Schwab's dial gauge had small increments, so that's about as close as I could see) - so I'm happy.
Some discrepancies between tire gauges and TPMS - What's the best gauge to use?
- Thread starter brasskey
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Here are the result of the test. I only tested 3 of the tires as the 4th was unnecessary. The test was done in my garage after the car sat for 10 hours. I didn't wait until morning when it would be cooler as this test was about consistency, not whether the cold pressure was spot on 42. After testing the 3 tires I immediately drove around the block (didn't even need to go that far) until the TPMS registered.
Tire Intercomp Rhino (Analog) ARB Inflator "Nozzle" (Analog) TPMS
LR 42.3 43 42.5 40
RR 42.5 43 42.5 40
LF 42.1 42.5 42 40
Bottom line
Also, TPMS is doing its job - warning me when I get below a certain threshold. This happens when I air down off road. Seems to kick in about 30PSI (according to its determination of 30 PSI which is actually about 32-33 PSI on my gauges.)
Tire Intercomp Rhino (Analog) ARB Inflator "Nozzle" (Analog) TPMS
LR 42.3 43 42.5 40
RR 42.5 43 42.5 40
LF 42.1 42.5 42 40
Bottom line
- My other, cheaper gauges were very close to the Intercomp. I trust the Intercomp but the marginal differences were not significant for my application.
- I don't need a $299 gauge. What I have is close enough. I will attempt to return it.
- TPMS is consistently 20-2.5 PSI lower than the other gauges.
- I will trust the other gauges and assume TPMS is always low - on my LC.
Also, TPMS is doing its job - warning me when I get below a certain threshold. This happens when I air down off road. Seems to kick in about 30PSI (according to its determination of 30 PSI which is actually about 32-33 PSI on my gauges.)
gaijin
GOLD Star
Thanks for reporting back.
Just out of curiosity, with the OEM Toyota TPMS sensors it is not necessary to drive to activate them - just turning the ignition ON will populate the display of the tire pressures. If you have to drive to activate yours, do you have aftermarket TPMS sensors?
TIA
As far as I know these are the OEM versions. I certainly haven’t changed them since I bought it. And as far as I remember they have always behaved this way. I don’t normally switch to the TPMS screen to watch them when I first drive away. But it only takes about 50 yds of driving. This is the 2016 model LC. TPMS shows all five tires. But I can also check the next time I am in the Toyota shop and see if Discount Tire switched them up on me. I can’t imagine they would do it without asking.
If rotation were a criteria for activating the sensors, wouldn't the spare never report pressure?
gaijin
GOLD Star
That's correct. That's why it is not necessary to drive to see the reported tire pressures with the Toyota TPMS sensors.
So I was wrong. And not wrong. 
It is not necessary for the tires/wheels to rotate to activate the TPMS on my 2016 LC. It just takes 30-60 secs and usually I am already moving by then so I thought it was the movement that made it active. I suspect it is just the system getting around to doing the wireless sync or something. I checked this by setting the MID to the TPMS display right after turning on the ignition. Then I waited. Nav system starts up, phone connects and soon after the TPMS starts displaying the PSI data.
That said, it is still 2-3 PSI below the Intercomp and each of the other gauges I have. I may have the Toyota guys take a look at this the next time i bring it in but for now I am going to assume that TPMS reads 2-3 PSI low and to trust my gauges if they are consistently 2-3 PSI higher than the TPMS.
It is not necessary for the tires/wheels to rotate to activate the TPMS on my 2016 LC. It just takes 30-60 secs and usually I am already moving by then so I thought it was the movement that made it active. I suspect it is just the system getting around to doing the wireless sync or something. I checked this by setting the MID to the TPMS display right after turning on the ignition. Then I waited. Nav system starts up, phone connects and soon after the TPMS starts displaying the PSI data.
That said, it is still 2-3 PSI below the Intercomp and each of the other gauges I have. I may have the Toyota guys take a look at this the next time i bring it in but for now I am going to assume that TPMS reads 2-3 PSI low and to trust my gauges if they are consistently 2-3 PSI higher than the TPMS.
Funny, I have had the same issue on both of our LXs here in Denver. They are both about 2-3 psi off from every gauge I have ever put on them. At first I also thought it was the gauges but after trying so many I just assume its the tpms and fill accordingly with the delta in mind.
I still wonder if there is some truth to the Discount Tire story that some systems haven't been calibrated or re-calibrated for elevation. But then my gauges that I buy on Amazon or wherever are properly calibrated? Maybe the TPMS is calibrated for elevation and the other gauges aren't?
Which begs the question. Does higher elevation generally mean you may need to add air or to remove air? If I set my tires at 42PSI at sea level, will they read 42PSI at 10,000'? (Assuming "cold" and all that.) Is my TPMS reading at 39 when my gauges read 42 mean that the TPMS is telling me to put more air in my tires when at 6,000'?
Theoretically air is less dense the higher you go. If you start with 40 psi as sea level you will be down at our elevation and would need to add more air. The calibration thing could be a possibility but you would think Toyota would have taken that into account. I know on my forced induction cars some of the electronic boost gauges do read high by a few PSI due to the elevation. Some can be re-calibrated but not all. After years of messing with them I just use analog gauges now as they always read correctly.
- Thread starter
- #31
Thank you @Dan Higgins for the analysis with the newer gauge. Guess I’ll stick to just having the gauges being a little off compared to TPMS.
