Tire Temperature

[Darrell]

I bought the TST tire monitoring system a couple weeks ago. I'm planning to install it before I pull out next week. The owners manual does not provide a recommended upper limit for the tire temperature before the alarm goes off.
Does anyone have experience with the maximum temperature for a tire?

[fonzie]

Default setting on my TST unit is 158 F. That is what is written in the manual. I have set mine at 130 F, as after a few years of use, tires temperature never exceeded 110 F on my trailer.

[SKnight]

You'll see a typical max of about 30* over ambient if you're inflated properly, and it will very a bit more than that on a hot sunny day that gets the pavement really hot, 100* ambient will see up to about 50* over.

[OldCoot]

Having used my TST for over a year and towing in 90+D ambient, I've never experienced anything over 115D. The default is 157D or 158D, so I set mine at 120D I think. I have found they will jump 5D real fast and then just ease up another 5D to 8D. I've found out a rest stop of about 20-30 minutes will cool them pretty quickly. I think the TST manual says the tire companies claim the tires start breaking down at 180D.

[f5moab]

Last year, before my Tireminder system failed, the max temps I saw on my tires was around 115. But when I set up my new TST sensors in a week or two, I will leave them at that 158 degree setting.

Honestly, not sure if temp is an important factor to monitor if you are monitoring the air pressure and making sure its cold setting is correct before pulling out and that it goes up normally during a trip and never starts to reduce while traveling.

Vehicle manufactures do not monitor the temps of the tires with the Federally required TP sensors.

I guess temps could start going up if a bearing starts to go bad causing more friction.

[youroo]

Temp is handy for wheel & brake info also,it transfers to the tire. Also the (Sun Side) will read higher temps going down the road. Youroo!!

[SKnight]

Actually factory TPMS sensors do relay tire temp to the vehicle, but only pressure is actively reported.

Honestly, you'll rarely see anything worth noting temperature wise. If a tire starts cooking it's either the hub/brakes burning it up, which is very helpful when it happens, or the tire is running out of air and is about to blow due to sidewall flexing. But, you should have heard the pressure alarm long before the sidewall started heating up noticeably.

[OldCoot]

Watch the pressure and temp rise if you go down a mountain and are using the brakes, they both will be higher at the bottom than at the top of the mountain.

[f5moab]

Originally Posted by SKnight

Actually factory TPMS sensors do relay tire temp to the vehicle, but only pressure is actively reported.

Let me rephrase. My GM sensors do not monitor the temperatures inside the tires. And FMVSS 138 (mandated by the TREAD Act) does not have a requirement for the monitoring of temps (or altitude) inside the tire. However, in the early days of the formation of FMVSS 138, there was a temp requirement but the Federal government dropped it since testing showed it meant nothing and added a complexity to the system that was not needed. However, I guess some manufacturers might use it.
And even GM might use it sometime in the future, but so far, not on any Silverados/Hummers up to 2013.

Originally Posted by OldCoot

Watch the pressure and temp rise if you go down a mountain and are using the brakes, they both will be higher at the bottom than at the top of the mountain.

Really have to heat up those brakes since the general formula is 1 lb increase in TP for each 10 degrees F in temps.

But honestly have never monitored the tire temps while coming down any of the high passes in CO/UT/ID/WY or MT. I downshift, only time I have had to apply brakes is if I come up on a slower moving vehicle and can't get around it due to heavy traffic in the passing lane.

[acadianbob]

Originally Posted by OldCoot

Watch the pressure and temp rise if you go down a mountain and are using the brakes, they both will be higher at the bottom than at the top of the mountain.

Interesting! Never thought of that. And it is likely to be warmer at the bottom too.

[SKnight]

Originally Posted by f5moab

Let me rephrase. My GM sensors do not monitor the temperatures inside the tires. And FMVSS 138 (mandated by the TREAD Act) does not have a requirement for the monitoring of temps (or altitude) inside the tire. However, in the early days of the formation of FMVSS 138, there was a temp requirement but the Federal government dropped it since testing showed it meant nothing and added a complexity to the system that was not needed. However, I guess some manufacturers might use it.
And even GM might use it sometime in the future, but so far, not on any Silverados/Hummers up to 2013.

You're sure of that?

This is my 2013 Impala, LF sensor, just a few moments ago. If you like I can measure my daughters 2010 Impala when she gets home.

I hate to say it, but most factory sensors do indeed broadcast temperature.

[f5moab]

I believe what you are reading is an ambient air temps of surrounding area and probably from the sensor in front of the radiator or the actual air temp sensor in the engine intake air stream. However, it is NOT a Federal requirement.

My Tech 2 does not show any tire pressure sensor temp for either of my two vehicles; however, it does display an ambient air temp reading. And the Tech 2 is the actual GM tool used by GM techs and engineering to read all data produced by the vehicle; short of that that requires more intensive hardware/software.

From GM documentation:
The tire pressure monitor (TPM) system warns the driver when a significant loss, or gain of tire pressure occurs in any of the 4 tires and allows the driver to display the individual tire pressures and their locations on the driver information center (DIC).

The system uses the body control module (BCM), driver information center (DIC), instrument panel cluster (IPC), remote control door lock receiver (RCDLR), a radio frequency (RF) transmitting pressure sensor in each wheel/tire assembly, and the serial data circuit to perform the system functions. Each sensor has an internal power supply with a 10 year service life.

When the vehicle is stationary, the sensors internal accelerometer is inactive, which puts the sensors into a stationary state. In this state the sensors sample tire pressure once every 30 seconds and do not transmit at all if the tire pressure does not change. As vehicle speed increases, centrifugal force activates the sensors internal accelerometer causing the sensors to go into rolling mode. In this mode, the sensors sample tire pressure once every 30 seconds and transmit in rolling mode once every 60 seconds. The RCDLR receives and translates the data contained in each sensors RF transmission into sensor presence, sensor mode, and tire pressure. The RCDLR sends the tire pressure and tire location data to the DIC via the serial data circuit where they are displayed.

The sensors continuously compare their last pressure sample to their current pressure sample and will transmit in re-measure mode if a 8.3 kPa (1.2 psi) change in tire pressure has been detected in either a stationary or rolling state. When the TPM system detects a significant loss, or gain of tire pressure, the tire pressure monitor indicator icon is illuminated on the IPC and if equipped, a check tire pressure type message is displayed on the DIC. Both the indicator icon and DIC message can be cleared by adjusting the tire pressures to the recommended kPa/psi and driving the vehicle above 40 km/h (25 mph) for at least 2 minutes.

If power is disconnected from the RCDLR or if the vehicle battery is disconnected each TPM sensor ID is retained but all of the tire pressure information is lost. Under these circumstances the RCDLR cannot assume that the tire pressures were maintained over an unknown period of time. If equipped, the DIC will display all dashes and the scan tool will indicate a default tire pressure value of 1020 kPa (148 psi) for each tire. Driving the vehicle above 40 km/h (25 mph) for at least 2 minutes will activate the sensors causing the DIC to display the current tire pressures. The EL-46079/J-46079 TPM special tool or the pressure increase/decrease method may also be used to activate the sensors as well.

The RCDLR has the ability to detect malfunctions within the TPM system. In the event a DTC is set, the tire pressure monitor indicator icon on the IPC will flash for 1 minute and then remain illuminated after the ignition is turned ON and the IPC bulb check has been completed. Any malfunction detected will cause the DIC to display a service tire monitor system type message. For more information on other functions of the RCDLR, refer to Keyless Entry System Description and Operation.


And reading over the Impala information, it says basically the same as for my 2013 Silverado. The difference between the Silverado and the Hummer is the Hummer does not use a RCDLR, signals directly to the BCM.

And from the TREAD Act, which mandated the TPMS requirement:
ETV requested that the agency reconsider its tentative decision in the NPRM to not include a requirement for temperature compensation as part of the TPMS standard. ETV argued that the standard must provide temperature compensation when the TPMS calculates tire pressure in order to determine the need for activation of the low pressure warning. According to ETV, temperature compensation is needed to account for the rise in pressure (4 psi) from the cold-start, ambient temperature to the normal running temperature.

ETV also stated that the TPMS should be required to account for changes in atmospheric pressure that accompany changing altitudes. ETV commented that such atmospheric pressure changes could change tire pressure by as much as 10 psi.

ETV argued that the TPMS should make the necessary adjustments to account for temperature, altitude, and load prior to vehicle motion in order to prevent nuisance warnings that may result from daily and seasonal variations in those factors and which eventually might cause the driver to ignore TPMS warnings. Alternatively, ETV argued that those factors could cause the TPMS low pressure telltale to fail to illuminate, thereby resulting in a false sense of security on the part of the driver.

We have decided not to adopt requirements for temperature and altitude compensation because we believe that such requirements would introduce unnecessary complexity to the standard. Regarding temperature correction, the test procedures for low tire pressure detection in the final rule have been amended to compensate for tire pressure fluctuation. Tires will be deflated to testing pressure within five minutes after a 20-minute period of driving, which will ensure that the tire pressure will not rise above the telltale activation pressure during the remainder of the test.

Regarding altitude correction, we do not believe that altitude will be a significant factor in tire pressure fluctuation. We expect that the effect of atmospheric pressure on tire pressure will not result in more than a 5-percent change in tire pressure over the atmospheric pressure extremes encountered during normal driving.

We note further that ETV did not provide any data to demonstrate the need for either temperature or atmospheric compensation.

But, I guess for conclusive proof, at least for GM vehicles, I can contact an ex-neighbor in Rochester Hills MI, who (at least when I lived there five years ago) was the head engineer for the tire monitoring system used by GM.
I will do that when I get the time. But for now, I do not believe that showing me a display from an aftermarket code reader/info display.

Have a nice night; I'm off to warm up my tires.

[SKnight]

I'm a General Motors World Class tech, ASE master tech, and now sell TPMS sensors for a living. I've spent more time with a Tech 2 in my hands than most techs. 23 years in this business so far, hope to call it a career in 20 more.

I promise you, that reading came right out of the sensor itself, especially considering my tool reads the broadcast info straight from the sensor without plugging into the ALDL port. The doors were locked even.

But get your engineer on the phone. Last one I spoke with I ended up betting him my paycheck against his that I was right and needed a VCI number to flash a problem out of a car. Two days later I had my VCI number, never could collect payment though.

Your move chief.

[SKnight]

Just for chuckles, I checked the Chrysler 200, Buick Enclave and Toyota Avalon sensors I carry around in my bag of tricks. All three broadcast temperature.

Does GM or any other manufacturer use it? Not really. Is it recorded in the data as part of a crash? You'll be hard pressed to find it officially, but I guarantee the NTSB can get to it after a crash.

[f5moab]

All I know for sure is my Tech 2 does not show a temp when reading the tire TP sensor, so maybe my Tech 2 is a POS or I have some strange TP sensors.

[OldCoot]

I got the popcorn concession for this one covered.

[garbonz]

Whoa der pardners. Woosers that a lot of information for us regulare folks.

I forgot the question.

[SKnight]

The factory might not use it. It might not be a viewable parameter. Remember, a Tech 2 only displays information that the engineers deem relevant to repairing a vehicle, there's so much information on an engineering level, that a Tech 2 can see with the proper access codes, but as an end user you'll never see. I had a field engineer come help me once, good golly the stuff he could see.

But they do broadcast temp. I don't want to say every, but most every sensor I've ever scanned with that tool does.

[SKnight]

Originally Posted by OldCoot

I got the popcorn concession for this one covered.

Haha, pass me some too!

Originally Posted by garbonz

Whoa der pardners. Woosers that a lot of information for us regulare folks.

I forgot the question.

Something about the max temp for a tire, it was stated that vehicle factory sensors don't monitor temp, I said that they actually do.

Then it went all pear shaped. I'm sorry for contributing to getting this so far off track.

[Airdale]

Excerpt from the Michelin Tire Service Manual.

“Generally, As a radial tire revolves during operation, heat is generated on the inside of the tire at 4 degrees per minute. However, the tire loses heat at the rate of 3 degrees per minute with dissipation throughout the casing and air flow around the tire. After 40 minutes of continuous operation, the temperature has increased 40 degrees Fahrenheit. As the temperature inside the tire increases, the inflation pressure also increases. Thus, a tire inflated to 80 psi cold would now be 85 psi. because the inflation pressure has increased, the amount of tire flexing has decreased, which decreases the amount of heat generated per minute to 3 degrees per minute. Assuming the heat dissipation factor is still 3 degrees Fahrenheit per minute, the net temperature change is nil (0). This is called thermal equilibrium.”

Airdale