: Can Tire Pressure Monitors Be Adjusted?



sefa01
02-16-05, 02:58 PM
As benjet pointed out, if you go with the F1 GS-D3s with rec pressure of 35 psi, the tire pressure monitors become useless as soon as they heat up and you get to about 42 psi.

Is there some way that the monitors can be adjusted so that the upper--and lower-ranges can be changed?

ctsvett
02-16-05, 03:21 PM
From what I understand you will probably need a tech II to do this (if it is posible). I remember the one-lap of america guys had this problem the whole time. The TPS system what beeping the entire race at them and it prevented them from going into Competition mode or turning off the TC.

I will check the SM though.

Reed
http://www.cadillacfaq.com

globed70
02-16-05, 04:45 PM
Even with the stock tires, GM recommends pumping up the rears for high speed driving (was it 34psi on the tag?)? That plus warmer weather on a given day had the damn thing beeping on me. Anyone with tech2 knowledge?

urbanski
02-16-05, 05:58 PM
yeah maybe some of our resident tuners can chime in :)

StealthV
02-16-05, 06:03 PM
Commercially available tuning software packages only adjust the powertrain control module and don't have read/write capability for the body control module which is where the TPS information is most likely stored.

A dealer service tool such as a Tech II might be able to do it. :hmm:

slow35th
02-16-05, 06:52 PM
What would happen if you ran nitrogen in the tires? Does it expand as much as air when heated?

A local chanel here ran a news report about Costco filling everyones tires with nitrogen instead of air. I does not contain as much moisture as air and is supposed to ad to the life of the tire.

StealthV
02-16-05, 07:07 PM
The air we breathe and also traditionally put into tires is already 78% (IMMIC) nitrogen.

Increasing the nitrogen level closer to %100 would help but may not be enough.

The higher the tire pressure when cold, the less heat build up in the tire and resultant increase in pressure. That is why Cadillac recommends the higher pressure for high speeds. I'd try a cold pressure reading around 37-38 to keep from activating the 42 PSI alarm.

CVP33
02-16-05, 07:22 PM
http://www.mistupid.com/chemistry/aircomp.htm

We need more Methane. I'm making some as I type this. :yup: Oops there's some more. :histeric:

Dreamin
02-16-05, 07:23 PM
It's not the O2 or N2 that increases the tire pressure when heated... its the water vapor. When putting "nitrogen" in tires, you're getting "dried" N2... no water vapor... which make a big difference... 1-2psi swing instead of the 8-10 psi swing with air.

slow35th
02-16-05, 07:39 PM
It's not the O2 or N2 that increases the tire pressure when heated... its the water vapor. When putting "nitrogen" in tires, you're getting "dried" N2... no water vapor... which make a big difference... 1-2psi swing instead of the 8-10 psi swing with air.

There ya go. Your solution is nitrogen. I'm going to see if I can get a tank of it or get one of my air tanks filled with it.

Lance

benjet
02-16-05, 07:57 PM
It's not the O2 or N2 that increases the tire pressure when heated... its the water vapor. When putting "nitrogen" in tires, you're getting "dried" N2... no water vapor... which make a big difference... 1-2psi swing instead of the 8-10 psi swing with air.

hmmm have to try that next, I hit the 42 level 2-3 times per week, esp with passengers/cargo (more weight), and freeway speeds.

2004ctsv
02-16-05, 09:20 PM
It's not the O2 or N2 that increases the tire pressure when heated... its the water vapor. When putting "nitrogen" in tires, you're getting "dried" N2... no water vapor... which make a big difference... 1-2psi swing instead of the 8-10 psi swing with air.

How does that work? I hope you have a water trap on you compressor.

Tony

Rich H
02-16-05, 10:05 PM
The key is relatively dry inert gas of any type. At constant pressure, most gases will expand and contract proportional to the temperature change per the ideal gas law (PV=nRT) including water vapor as long as it isn't present in large concentrations. If there is a lot of water vapor the problem will be condensation at low ambient temps which removes some of it from the gas phase. At constant volume (in a tire) this lowers the pressure more than just gas phase contraction would as the temp drops.

This is what might cause the large pressure swings as the tire heats up with driving since the condensed water would re-vaporize and add to the number of moles of gas (n in the equation). The gas pressure would go up more than that just attributed to the temp rise in the equation.

Bottom line: use dry air or nitrogen from a compressor system that has at least a dessicant dryer upstream of the receiver. Or dry bottled gas.
:thumbsup:

2004ctsv
02-16-05, 10:33 PM
The trick is cool (room temp or less) air. You only get into trouble with compressors that have small receivers and send hot humid air into your tires.

I started writing a thesis here to explain but it got too long so I erased it. I did convince myself that with wet air and pressure leakage from the tires that you could have a potential problem with condensate in the tire giving greater than expected pressure rise when the tires get hot. And that's long winded enough.

Tony