PSA: Time to Pump Up Your Tires!

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David Towle

Well-Known Member
I assume everyone here is concerned with fuel (gas/electric) economy. Autumn is the time, due to falling temperatures, when you must regularly add air to your tires (preferably first thing in the morning when tires are coldest). In fact I go above the recommended level a few PSI this time of year to make sure I don't fall behind.

For those interested, this is due to the Ideal Gas Law, PV=nRT. The only letters on this you need to know is P on one side of the equation and T on the other, meaning that when temperature goes down pressure goes down. Air is not an ideal gas but its not far off either.

Where I live the total difference from summer to winter is about 6 psi so its not minor.
 
Will the TPMS system tell me when it's needed, or should I check on my own?
(Today it's a balmy mid 60's, but last week we dropped into the 30's, no TPMS warning yet.)
 
The TPMS system does not actually monitor tire pressures, it only looks at tire rotational speed and will alert you when one is different enough from the others.
If all tires are at relatively the same pressure (even if too low) the Clarity assumes nothing is wrong. This type of system uses existing sensors (ABS/Stability Control) instead of a device in/on the wheel itself that transmits pressure readings.
 
Now we have a feature that is more useless than the Eco Score.

I check pressure monthly, but will now put the valve stem mounted TPMS sensors on the Clarity, that we use on the vehicle that we tow behind the motorhome. We’ll never use both cars at the same time and it is a 2 minute swap out. Maybe Honda should have called Jeep 5 years ago to learn about this advanced technology.
 
I bought one of these a year ago. Happy driver. I've already added air this fall. Also the car's TPMS system has gone on alert when there was no problem. Just did the recalibrate routine.
 
DucRider said:
The TPMS system does not actually monitor tire pressures, it only looks at tire rotational speed and will alert you when one is different enough from the others.
If all tires are at relatively the same pressure (even if too low) the Clarity assumes nothing is wrong. This type of system uses existing sensors (ABS/Stability Control) instead of a device in/on the wheel itself that transmits pressure readings.
Click to expand...
Not only that, but I think it takes a big difference for the low pressure to show up. Yes it is close to useless, but this doesn't matter to me as I'm an old fashioned manual pressure monitor.
 
David in TN said:
... TPMS works on rotational difference between the tires.
Click to expand...

Not in any modern system. Pressure and temperature are read directly and
transmitted to the car's pickups. As much as manufacturers tried to do TPMS
via wheel-speed sensors and clever software, they eventually admitted
defeat and the NHTSA mandated direct read.

However, there's this ...

_H*
 
hobbit said:
Not in any modern system. Pressure and temperature are read directly and
transmitted to the car's pickups. As much as manufacturers tried to do TPMS
via wheel-speed sensors and clever software, they eventually admitted
defeat and the NHTSA mandated direct read.

However, there's this ...

_H*
Click to expand...
My solution is a whole lot easier than this!
 
David Towle said:
I assume everyone here is concerned with fuel (gas/electric) economy. Autumn is the time, due to falling temperatures, when you must regularly add air to your tires (preferably first thing in the morning when tires are coldest). In fact I go above the recommended level a few PSI this time of year to make sure I don't fall behind.

For those interested, this is due to the Ideal Gas Law, PV=nRT. The only letters on this you need to know is P on one side of the equation and T on the other, meaning that when temperature goes down pressure goes down. Air is not an ideal gas but its not far off either.

Where I live the total difference from summer to winter is about 6 psi so its not minor.
Click to expand...

Good advice. I think it also recommended to recalibrate the TPMS after adjusting tire pressure.
 
I'm another fan of the add-on valve cap TPMS system. These things are cheap, like $20. I bought one on Ebay that has the small solar panel on it. Stick the monitor on the dash to the left of the steering wheel and under the windshield enough to keep it charged with daylight. Never needs power from USB. Automatic shut off at night and turns on based on sound of the door opening (I think that's what seems to activate it anyway). Anyway, had mine about 6 months now and no issues whatsoever...
It is similar to this one...
https://www.ebay.com/itm/Wireless-S...toring-System-4-External-Sensors/372836527061
 
hobbit said:
Not in any modern system. Pressure and temperature are read directly and transmitted to the car's pickups. As much as manufacturers tried to do TPMS via wheel-speed sensors and clever software, they eventually admitted defeat and the NHTSA mandated direct read.
Click to expand...
The Clarity actually does check each wheel's speed to see if any tires have inconsistent dimensions. That's why the calibration procedure is required.
From page 32 of the Clarity Plug-In Hybrid Owners Manual:

upload_2019-11-11_21-53-43.webp
 
Last edited:
hobbit said:
Not in any modern system. Pressure and temperature are read directly and
transmitted to the car's pickups. As much as manufacturers tried to do TPMS
via wheel-speed sensors and clever software, they eventually admitted
defeat and the NHTSA mandated direct read.



However, there's this ...

_H*
Click to expand...

A few folks here have posted that Honda uses the rotation method. And Honda put out a video explaining it.

It definitely is not a “modern” system.
 
Groves Cooke said:
Honda knows about it. I had individual tire pressure read outs on my last TLX. Also had a good rear cross alert on that car.
Click to expand...

Don't forget - Clarity was pretty much designed in 2014/15 - and has all of Honda's latest tech from that date...
 
Jeez, thanks for the replies. I came from a 2007 Tacoma and Prius Prime, both had actual tire pressure monitors in the tires. I guess the upside is that I don;t have to replace the monitors when they break in about 8 to 10 years.
 
Kerbe said:
Don't forget - Clarity was pretty much designed in 2014/15 - and has all of Honda's latest tech from that date...
Click to expand...

That may be true, but we’re talking about a TPMS that actually measures tire pressure and shows it on a display for the driver. This technology was available and used on Honda/Acura vehicles (and other manufacturers) prior to 2014/15. It’s a pretty simple add-on.

My car was built in May of 2019.
 
Landshark said:
That may be true, but we’re talking about a TPMS that actually measures tire pressure and shows it on a display for the driver. This technology was available and used on Honda/Acura vehicles (and other manufacturers) prior to 2014/15. It’s a pretty simple add-on.

My car was built in May of 2019.
Click to expand...

The TPMS in my 2010 Fit - and also in my 2016 VW Golf - required me to balance the pressure in all four tires and then only reported when one or more of them dropped below a certain percent. Those systems did not indicate which tire or how much of a drop in pressure occurred. It the Fit, one of the in-tire sensors went bad, disabling the whole system. My point about Honda tech in Clarity was that the vehicle was a test-bed for many different engineering ideas - like the aluminum body panels and the GFC bumper beam - and, maybe, some engineer thought this would be a new and exciting way to gauge tire pressure.
 
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