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jjrbus

FT Myers FL

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Posted: 09/25/22 07:05am Link  |  Quote  |  Print  |  Notify Moderator

EEZ 518C with 4 sensors

I put my Roadtrek in storage for about 2 months and removed the system brought it home.

Sitting in driveway with cold tires, Inflate rear tires to 80 psi and front tires to 55 psi. Monitor is showing 49 and 51 front tires 74 and 76 rear tires. There is no way I am losing that much psi putting the sensors on the stem. I would never call this system 100% accurate but have not seen it this far off before, I also took it for a ride psi raised as expected but still off.

Before you ask, I have a high quality dual foot inflator with oil filled gauge verified with a cheap Slime pressure gauge.

Looked all over the net for what is wrong and see nothing, nothing in the manual either?

wa8yxm

Davison Michigan (East of Flint)

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Posted: 09/25/22 08:00am Link  |  Quote  |  Print  |  Notify Moderator

Ok was that INSTANTly or was that "Next morning".

Both cases.. When you add air to the tires the air is HOTTER than the air you are breathing (Effect of compression. gets hotter) than as you screw on the sensor and move to the display.. The tire cools and pressure goes DOWN.


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jjrbus

FT Myers FL

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Posted: 09/25/22 08:55am Link  |  Quote  |  Print  |  Notify Moderator

Good point, I will have to tinker with this today. Pulled 2 sensors and only one is showing the correct psi on the monitor.

opnspaces

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Posted: 09/25/22 09:10am Link  |  Quote  |  Print  |  Notify Moderator

It seems that if he pressurized all the tires at the same time then all the readings should be the same.

OP how soon after you filled the tires did you you screw the sensors on? I can see possibly letting everything sit for an hour before you screw the sensors on you might have differences due to temperatures. But if you screwed the sensors on right after inflating the tire I would say the sensors are wrong.


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Gdetrailer

PA

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Posted: 09/25/22 11:17am Link  |  Quote  |  Print  |  Notify Moderator

Cold as in you did not "move" the RV from where you parked it the night before?

If so those were the "last known" readings from the night before.

Sensors are designed to "go to sleep" when the wheels top turning after a preset amount of time.

You typically need to drive for 10-20 minutes above 20 MPH to "wake up" the sensors. Once woke up they will report the updated readings to your display.

As far as pressures not being "even", this happens a lot when you have one side exposed to a higher temp as the sun hits it. Even just a little more direct sun on one side can heat the air in the tires on that side enough to give 5 lbs or higher pressure reading.

You almost need to check the pressures when it is overcast, early in morning or later at night or whenever you have less direct sun hitting any of the tires.

wa8yxm

Davison Michigan (East of Flint)

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Posted: 09/25/22 02:30pm Link  |  Quote  |  Print  |  Notify Moderator

opnspaces wrote:

It seems that if he pressurized all the tires at the same time then all the readings should be the same


It does dosen't it
But he did not pressurize them at the same time
he did one, then he did the next, then he did the one after that.

jjrbus

FT Myers FL

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Posted: 09/25/22 03:00pm Link  |  Quote  |  Print  |  Notify Moderator

Tanks for the responses, greatly appreciated.

Color me confused. Van has been sitting since yesterday. PSI is not what I set it too yesterday

I checked pressure all 4 tires with monitor in my hand. Monitor is showing same pressure as tire gauge. I can live with this.

Gdetrailer

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Posted: 09/25/22 03:32pm Link  |  Quote  |  Print  |  Notify Moderator

jjrbus wrote:

Tanks for the responses, greatly appreciated.

Color me confused. Van has been sitting since yesterday. PSI is not what I set it too yesterday

I checked pressure all 4 tires with monitor in my hand. Monitor is showing same pressure as tire gauge. I can live with this.


How Weather can change tire pressure HERE

"You're not imagining things — your tire pressure is shifting with the weather. As seasons change and temperatures fluctuate, you'll likely experience varying levels of PSI.

Why Does Tire Pressure Change?

When air molecules experience cold temperatures, they move slowly and stick closer together — taking up less physical space. In warmer temperatures, air molecules move quickly and spread out more — taking up more physical space.

When the air molecules inside your tires heat up, they expand, often leading to increased tire pressure.

As you might expect, the opposite is true for cold air. If the temperature outside drops suddenly (like it does overnight in the fall and spring seasons), the air in your tires can become condensed, leading to a loss of pressure.

The relationship between PSI shifts as temperature changes:

Higher temperatures = higher pressure and overinflation
Lower temperatures = lower pressure and underinflation

"


There is a direct relationship in the ambient tempurature vs air pressure.

Spring and fall can especially play mind games on you because of the large temperature changes that can happen from the time you check, fill, adjust the tires to the next time you check the tires pressure.

That is why I mentioned even direct sun hitting one side of your rig can give you a different reading from what you get on the side with no direct sun.

Tire manufacturers do not really specify what "cold temperature" is other than not being driven for a certain amount of time and basically is the tire temperature that is equal to the outdoor air temps..

Take your best guess and roll with it, with no sun directly hitting any of the tires set the pressure to your desired level while the tires are at ambient air temps.

The pressure can go up as the tire warms and can go down as the tire cools and if the ambient air temps goes up or down your pressure will follow that.

Don't overthink, you will see some variations in pressure even when driving according to the loads on each tire.

If you are concerned that your sensors may have an issue, in your case you can use the same tire and one at a time install on the stem and take reading.. If all readings match you are good. If readings are off (don't match) then perhaps you have a sensor that isn't calibrated well.

jjrbus

FT Myers FL

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Posted: 09/25/22 07:10pm Link  |  Quote  |  Print  |  Notify Moderator

When I got my first TPMS it left me at a loss. I had no idea properly inflated tires psi could be all over the place. To make it worse it was an inaccurate cheap unit.

I do not know what changed but yesterday the monitor was not showing the same psi that was in the tires, today they are spot on!

Tom_M

New Hope, MN

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Posted: 09/26/22 03:04am Link  |  Quote  |  Print  |  Notify Moderator

Swap sensors. If reading 49 51 before swap and 51 49 after, then problem is with sensors. If the same, problem is with monitor.


Tom
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