Tire Pressure Monitoring System

[Let’s Roll]

Reducing the air pressure in the tire to zero and then inflating it with just nitrogen will result in about a 95% concentration. Repeating the process two or three times can raise the concentration to about 98%.

My background was aviation, both military and civilian and we always serviced the tires with nitrogen.

Nitrogen filled tires are advantageous because nitrogen gas doesn’t support moisture or combustion. Compared with ambient air – which contains roughly 78 percent nitrogen, 21 percent oxygen, plus miscellaneous gases – pure nitrogen is an inert, non-flammable gas. Essentially, it’s dry air with the oxygen wholly removed.

If I could find a place that could fill the tires with nitrogen I’d do it. Alas, I’m sure the salesman would pitch the “added benefit of the super-duper” nitrogen package for an additional $150 or something crazy. Haha

 

[NY_Dutch]

Since TST did away with the extra rotating security cover on their valve cap sensors making them lighter, they no longer require metal valve stems:

 

[NY_Dutch]

My background was aviation, both military and civilian and we always serviced the tires with nitrogen.

Nitrogen filled tires are advantageous because nitrogen gas doesn’t support moisture or combustion. Compared with ambient air – which contains roughly 78 percent nitrogen, 21 percent oxygen, plus miscellaneous gases – pure nitrogen is an inert, non-flammable gas. Essentially, it’s dry air with the oxygen wholly removed.

If I could find a place that could fill the tires with nitrogen I’d do it. Alas, I’m sure the salesman would pitch the “added benefit of the super-duper” nitrogen package for an additional $150 or something crazy. Haha

The truck shop that does most of my RV work that I can't do myself fills all tires with nitrogen after mounting at no extra charge. Since they have their own on-site nitrogen "generator", they also run the air tools on nitrogen, saving the cost of installing and maintaining moisture separators, etc. They've also found that spray painting with nitrogen has several advantages over air as well.

 

[RVfixer]

The rotating security caps are easily removed. The caps were removed on one of the systems noted above where the sensor caused a rapid flat due to the sensor vibration on the rubber valve stem. I would never put them on rubber stems. In my opinion you are way safer with no TPMS than with sensors on rubber valve stems.

 

[Mark_K5LXP]

I noted that there are a couple "nitrogen stations" at my local costco, free for members. So no matter your view on nitrogen fill, you're not swiping your credit card or shoving money into a gas station air compressor.

Mark B.
Albuquerque, NM

 

[JayArr]

Aren't the "pro" sensors mounted to the inside of the rim away from the tire completely?

 

[NY_Dutch]

Aren't the "pro" sensors mounted to the inside of the rim away from the tire completely?

Some of factory and aftermarket inside sensors are part of the valve stem. Other sensors attach to the inside of the rim by a band around the center hub. TST is one of the few aftermarket TPMS vendors that offers a choice valve cap, flow-thru, and internal band sensors.

 

[JayArr]

Thanks NY_Dutch! The TST 507 system looks like what I need. 8 internal bands, a repeater to boost the signal from the trailer and a full color dash display receiver.

 

[DonTom]

the TPMS manufactures not to put sensors on rubber stems.

Yep, and every one of them. Disclaimer BS for the most part, IMO. But I wouldn't use the heavy & large sensors (such as the anciently designed Pressure-Pro)on rubber valves stems.

And I will check the stems often. And replace them with metal ASARP. Such as the first tire change.

-Don- Reno, NV

 

[NY_Dutch]

Yep, and every one of them. Disclaimer BS for the most part, IMO. But I wouldn't use the heavy & large sensors (such as the anciently designed Pressure-Pro)on rubber valves stems.

And I will check the stems often. And replace them with metal ASARP. Such as the first tire change.

-Don- Reno, NV

As I noted above, TST 507 valve cap sensors have no rubber stem restriction.

 

[Rob&Deryl]

I have the TST 507 flow through sensors on my trailer with metal stems. I also use the IR gun on occasion for peach of mind. Why? I look for hot hubs and wheels which might indicate dragging brakes or failing bearings. The TST system also shows me tire temperatures and if I see one tire hotter than the rest, at next stop will get out the IR gun.

 

[NY_Dutch]

I have the TST 507 flow through sensors on my trailer with metal stems. I also use the IR gun on occasion for peach of mind. Why? I look for hot hubs and wheels which might indicate dragging brakes or failing bearings. The TST system also shows me tire temperatures and if I see one tire hotter than the rest, at next stop will get out the IR gun.

Yes, the temperature display feature has alerted me to a failing wheel bearing on a previous toad as well as a sticking wheel cylinder on our motorhome.

 

[Punomatic]

But the only installation for most of the aftermarket TPMS systems is to screw the sensor on each tire and put the monitor in the cab (truck or motorhome), then set the monitor for the pressures and temperature limits that you want.

I might add that you should have metal valve stems when installing TPMS senders. The centrifugal force on the senders will cause bending and "flapping in the breeze" with rubber valve stems. JMHO

 

[jadatis]

So how does the infrared temp gun work? Is there a conversion chart for temps vs tire pressure?

For temperature of the gascompound vs tirepressure I made a simple list.
In that search cold pressure you fill at 70 degrF, and read the degrF/psi and remember that or write it down, for every axle .
Then while driving you can calculate roughly by head what temperature the inside tire has.
Example: your front-tires you use a cold pressure of 80 psi.
Look in the list, from 78 to 86 psi it gives 5.5 degrF/1 psi.
You read while driving 90 psi from tmps system.
Then 90-80= 10 x5.5 degrF = 55 degrF more then 70 degrF= 125 degrF. See you can do it by head.
it dont even have to be that accurate.

If you use an IR gun its yust where you aim on.
If on treath colder then inside air because of isolation of rubber.
At the sidewalls is better, but mayby at the rimmpart close to the tire gives probably closest to the real tire inside gascompound temperature.

Temperature reading of external tmps sensors is not that accurate, because it gives the temperature at the end of the valve, then calculating it back from the pressure rising is better.


35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi
149 psi/ 3 F/psi
177 psi/ 3 F/psi

 

[Larry N.]

Jadatis, most TPMS units today let you read temp alongside the psi.

 

[jadatis]

I know, but on RV often aftermarket tmps with external sensors screwed on the valves.
Then temperature reading is something in between inside and outside tire temperature.

 

[Let’s Roll]

This has been a great thread and I’ve learned a lot. I checked and I do have metal stems, just not sure which system to get, the TST or Eezrv.

 

[jadatis]

Dont take tmps for normal cars, they sometimes only go to 65psi, and you need system that goes up to 110 psi, and warm even more.


Someone wrote about pressure/ hight relation.
TMPS sensors send absolute pressure to the receving unit, wich substracts a standard 14.7 psi ambiënt outside pressure at sealevel.
At hight the absolute pressure stays the same ( at same temperature) but the outside pressure lowers to fi 11 psi.
Then you still read 90 psi if filled cold at sealevel at same temperature With TMPS. But when you check it with a gauge , wich measures what pressure in tire is more then outside pressure, it reads ( if 100% accurate, haha forget it) 93.7 psi.

There is a theory that absolute pressure gives the deflection, so heatproduction, so at hight you still need the 90psi+14.7 psi = 104,7 psi absolute pressure at same temperature.

So you dont have to compensate anything when reading TMPS , but with gauge you have to fill that 3.7psi higher.
But mostly at that hight that gives 11psi outside pressure, its colder, so pressure is lower.
Then you read that 1 psi/5 degr F lower, as I gave in the list for 90 psi .

Then that part you can compensate for riding quality and fuell saving, but to my discussable conclusion it is not needed for savety of tires, so they wont overheat when driving the speed constantly , the pressure is calculated for, because cooling down of tire is also better then.
But thats another story .

So you see TMPS gives also new worries, and chanche on acting wrong to laws of nature, but if you know what peculiar differences, you dont worry anymore, and you can let TMPS do what its made for, and that is warning for sudden pressure loss.
Most sensors give every minut or so the pressure and temperature to the receving unit , but when 2psi sudden pressure loss it sends direct, and receving unit translates that to emergencywarning of sudden pressureloss.

In the other topic I gave my mailadres cripted, can send you mailconversation with man of tiremoni system about tmps.
Begins in Dutch but switched over to English, so you can read it.

 

[Gizmo]

You'll find varying opinions, but most folks that I'm aware of suggest they're a good bet. Since one blowout can, besides the road service and tire price, cost several thousand dollars from damage to the RV I feel it's good insurance. In addition to the TPMS, I also check the tires visually and with an IR gun at every stop, even rest areas, along with a general walk-around of the coach and toad, just in case. It doesn't take long.

But the only installation for most of the aftermarket TPMS systems is to screw the sensor on each tire and put the monitor in the cab (truck or motorhome), then set the monitor for the pressures and temperature limits that you want.


You aim it at the tire (and wheel hub for me, too) and read the temperature displayed. Repeat for each tire and wheel.

There can't be a temperature to pressure conversion chart, because the only correlation is that, compared to the cold pressure at the beginning of the day, temperature rise will increase the pressure in the tire to some extent, partly due to tire friction on the road and partly due to the sun and to the day warming up. But it won't be a huge increase. In my 22.5" tires it will vary from 3-4 psi rise to maybe 10-15 psi if it's really hot. But psi also changes with altitude changes, and will be different on the sunny side vs the other side. The amount of change is also different on my rear tires than on the front, at least partly because my rears start the day about 85 psi and the front around 110 psi. Plus, the inside dual might be a tad different from the outside.

So I prefer to have the TPMS. Ours is a TST with TST-507 sensors.

I agree, never leave home without one - cheap insurance. We also have the TST and it has performed well for us and I really have found benefit with the color display over the b/w displays which in some bright light can be difficult to read.

 

[iristhomas112]

I demanded a TPMS for my auto to import from Canada to the US. The Kai dealer and utmost stores told me it could not be added after the request. You were wrong! As a result, my auto was imported without any problems. I paid for a shop to install it to produce a paper train, but indeed I could have done it myself! I'll also be buying another one to import my son's auto!