<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PARAGON:
No, actually I blame GM. The NHTSA does not require it to operate at all times and does not specifically say that there can't be something used to consider what the vehicle is doing. </div></BLOCKQUOTE>
Please, supply me with the exact NHTSA regulation that states this (rhetorical question since I will answer). The regulation does not actually state GM cannot add a switch for off-road purposes; however, in this day-and-age of our great court systems, GM and other manufacturers are probably a little gun shy in installing a switch that would enable someone to turn off something required by a Federal Regulation. Most of the car manufacturers are tired of being sued for even those mistakes created by the operator of a vehicle. Even if GM wins, they lose millions to defend these types of lawsuits. Therefore, installing such a switch would open GM up to liability. Litigation costs are passed onto the consumer. (As for how long they are to operate, see the reference under the actual Federal Regulation at the bottom of this message.)
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PARAGON:
As a matter of fact, if I remember correctly, the NHTSA allowed 2 types of pressure monitoring. One that actually measure the pressure itself and the other that measures harmonic frequency and/or uses wheel speed sensors from ABS or something along those lines. The second type would require it to operate only at a higher speed which is what should happen with off-road capable vehicles, at least. </div></BLOCKQUOTE>
You do remember correctly; however, you are living in the past; to be exact, prior to 2003. You are remembering the first regulation (issued May 2002 and required by the Federal TREAD act) issued by NHTSA that required tire pressure monitoring system in vehicles staring with the 2003 model year. Problem is that a NY Federal Appeals Court ruled the regulation invalid in 2003, due to the averaging system you mention; requiring NHTSA to go back and rewrite the regulation. The new regulation (written as 49 CFR, Parts 571 and 585), was not approved until April 8, 2005, with an effective date of September 2005 (cannot remember the exact date).
The averaging system you mention, that was ruled invalid by the Federal Court was not accurate for determining a low pressure in one tire. This inaccuracy was not due to the system itself; this was a system that had been used on many cars in the late eighties to early nineties. However, there was one large fault, and that fault was the operator/owner of the vehicle. Since the systems operated by sensing a difference in tire rotation between the four tires, it could not signal that all the tires were low. Therefore, if all the tires were running at 20 psi, but were supposed to be at 30 psi, the tires were operating at a dangerous pressure. (NHTSA, in June 2005, conducted a survey of 11,500 vehicles that indicted 26 percent of passenger cars and 29 percent of light trucks had at least one tire that was 25 percent or more below recommended inflated pressure.
Therefore, with the tires at 20 psi, the owner loads up the vehicle 20% over the maximum load, and heads out across the desert on a 100-degree day, there is a good chance they will not reach their destination. Low-pressure tires flex, this flex creates friction, friction creates heat, and that plus a nice hot road with nice hot ambient temperatures create the tire’s carcass to eventually give out and go boom. Best scenario is a flat tire, worse scenario is a rollover and people are killed. Therefore, this type of system was excluded from the future regulation.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PARAGON:So, good job sticking up for the employer, but GM knew this regulation was coming a long time ago and could have prepared better for it. Passing the buck won't cut it here. Just the same with DC/Jeep, Ford and the imports that are built for off-road. </div></BLOCKQUOTE>
Thanks for the compliment, but I would stick up for any car manufacturer when it comes to what I consider ridiculous Federal Regulations. The manufacturers knew the regulation was coming, and then it was changed. They also knew there were systems being used and newer ones that were available that they were going to use when the regulation took effect. However, like I stated earlier in this message, due to our litigious society, I believe the manufacturers are a little leery of installing something that would allow the system to be compromised, and in fact, in some courts, it might even be ruled illegal, since it would be up to the consumer to turn the switch back to allow the system to operate. Remember many Juries like to side with the little person who is suing the “big pocket” manufacturer, even if it is what I would classify as a frivolous lawsuit.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PARAGON:
Just so happens the H3 is the first that I have heard of that has the system and it seems to not accomodate. </div></BLOCKQUOTE>
This statement is a bit confusing from someone who appears to keep up with technology, so I might not be interpreting it correctly, and if I am incorrect in my assumption, I apologize. It appears you have not kept up with tire pressure-monitoring systems that have been used for many years. This type of system has been used in Corvettes since they started running runflat tires, and GM has had them installed in other cars such as Cadillac, prior to the regulation taking affect. Mercedes, Porsche, BMW also use separate sensor systems; I could go on-and-on.
(My 2003 Vette has a system that not only detects under inflation, it also detects over inflation. It will signal at less than 25 psi and greater than 36 psi. Originally, it was designed due to the runflat tires that could have zero pressure and yet look just like the other tires with 30 psi. However, many Vette owners, me included, pull the noisy, hard riding runflats off the car and install better tires, and we use the monitoring system to let us know if we have a slow leak that needs a patch/plug.)
Only new thing about this system (H3) versus the one on my Vette is that this system allows for self-learning of the sensors. On my Vette, if I switch sensor locations on the car, I have to use a magnet to recalibrate the sensor to that corner of the vehicle. Not really a problem since the tires cannot be rotated (17” front/18” rear). The C6 Vette requires a RF frequency generator to calibrate the sensors to each corner of the vehicle.
The system used on the H3 can utilize this same frequency generator to calibrate a sensor to each corner of the vehicle; however, if also allows for the computer to reason after a set mileage to recognize which sensor is at which wheel. This is primarily due to the spare, which has a sensor, but the sensor is not monitored until it is installed on an axle. Therefore, if you rotate the tires, or use the spare, you will receive a message that indicates there is a problem with the system, however, after a set amount of miles, the system will re-calibrate itself, turn off the message, and monitor the system as required by Federal Regulation.
The Federal Regulation itself:
Basically, the regulation states that vehicles beginning with the 2006 model year, must have a system that uses independent sensors that can detect when ONE or MORE of the vehicle’s tires are greater than 25 percent below recommended inflation pressures of the tires on that particular vehicle. However, the actual Regulation has a phase-in period that requires 20% of 2006 vehicles to have the system, 70% of 2007 vehicles, and 100% of 2008 vehicles.
The system must signal when a tire (or any number of tires) drops 25 percent below the recommended inflation pressures for the tires on the vehicle. So, if the recommended pressure is 30 psi, the sensor should signal at 22.5.
The system is only required to work with original tires and rims. SEMA and the auto manufacturers pushed this requirement. It would be next to impossible to certify a system to operate on all rims manufactured, and especially impossible to certify on rims not manufactured at the date of certification. From SEMA’s point of view, it would be too costly for rim manufacturers to comply. From the auto manufacturer’s point of view, it would be next to impossible to comply. As for tires, unless the tires are extremely low profile and the sensors are required to be removed due to clearance issues, these sensors should work with almost any replacement tire made.
The detection period is a maximum of 20 minutes. Meaning the system can be calibrated to ignore a low reading for up to 20 minutes. This will help to prevent the early cold morning under inflation syndrome. Since tire pressures drop one degree for each 10-degree drop in air temperature, this will help reduce the drives to the dealership when a tire is low. If your sensors are programmed for 25 psi and you park the car at night and it is 60 degrees outside, and your tire pressure is at 26 psi, and you get up the next morning and the ambient temperature is 40 degrees, your tire pressure will read 24 psi. If the system is allowed to wait twenty minutes before signaling, the tire will most likely warm up as it is driven and go above the warning set point of 25 psi.
There are also requirements in the final ruling that specify indicator light color, location, message warnings, etc. If anyone is interested in reading this document, refer to the CFR and have fun.
I apologize for the long post.