Change is a constant with TPMS technology: What will the future hold for indirect and direct systems?

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Change is a constant with TPMS technology: What will the future hold for indirect and direct systems?

As far as milestones go, the significance of Aug. 31, 2007, will be virtually unknown to most of the population. But by the time you read this publication, every new vehicle manufactured for sale in the United States will have a tire pressure monitoring system, or TPMS.

And we are certain that the new car manufacturers will remember this date forever, because it signified the last day a vehicle could be built without a system to warn the driver of an under-inflated tire.

I'm fairly certain that most tire dealers in North America have at least seen a car, light truck, mini-van or SUV with a TPMS by now. After all, the phase-in period officially began in 2005, and there are now millions of vehicles on the road with direct and indirect tire pressure monitoring systems. Since the number appears to have an indefinite growth rate at this point, tire dealers will have to deal with the impact tire pressure monitoring systems will have in their service bays.

It has been said many times by people smarter than me that the key to understanding the future is to look at the past, so let's see if that approach can clear the muddy water we're currently staring at in disbelief.


Phased and confused

To begin with, there were a number of reasons for the phase-in period. First and foremost was the simple timetable for building vehicles. Engineering takes place years ahead of actual production, so as you read this today, the plans for the 2011-13 vehicle models are currently on the drawing board or nearing completion. The 2009 and 2010 models are finished.

Soon after the TPMS legislation was passed, the car manufacturers basically had to retrofit certain platforms to support it. That's happened before, such as with the electronic control unit, or ECU, which is used on one model for the remote control door locks and for the headlights on another model from the same manufacturer.

In a perfect world, I'm positive that the new car companies would have preferred a more gradual phase-in schedule so that the reverse engineering which took place could have been avoided or at least minimized.

But that's not how Congress envisioned the grand TPMS plan of saving motorists from the dangers associated with under-inflated tires. They ordered the National Highway Traffic Safety Administration (NHTSA) to make it happen as quickly as possible, which should help explain the myriad of systems and procedures.

From that standpoint, NHTSA officials didn't have a choice in the matter. They were issued a directive and, like the good civil servants they are, they carried it out. My guess is that they would have liked a more reasonable phase-in schedule, but that's not how the system works.

In other words, it's all the government's fault, so blame the politicians. I'll jokingly say that to groups when I'm doing a TPMS presentation, but there's a certain amount of truth to the statement.

Indirect vs. direct

Another reason for the current discombobulated state of the TPMS is the fact that some new car companies banked on indirect systems as the solution to the problem. But the inability to detect four equally under-inflated tires in the first generation of monitoring systems, and that consumers would be forced to pay for the anti-lock brake system (ABS) upgrade, led to lawsuits that eventually caused NHTSA to change the requirements.

As it stands today, and probably forever, the TPMS must notify the driver when any tire is 25% below the placard. There is no mention of technology, so car manufacturers can use whatever method they prefer to meet the requirements of the standard.


So, what motivates a car manufacturer to require the choreographed routine of turning ignition switches on/off and stepping on the brake pedal, scrolling through multiple menus on the Driver Information Center (DIC), or holding magnets near the valve stem until the horn chirps?

Since you're never supposed to answer a question with a question, I'll answer it with two questions. Does the simplification of TPMS relearn procedures help sell cars? Does it cost more money?

If the answer to the first question was "yes" then there wouldn't be a second question. But the answer is "no," so vehicle manufacturers view it in different ways. Some are trying to meet the federal requirements for tire pressure monitoring systems as inexpensively as possible. Others have chosen to spend a few extra dollars to eliminate the choreography and allow technology to do all of the work.

Until now, direct TPMS technology was the only approach to meeting the federal guidelines for notifying drivers of under-inflated tires. In most instances, a sensor attached to the valve stem is used, but many of the 2006 and later Ford vehicles have re-introduced the band-mounted sensor. I also hear a lot of rumblings from the field about band-mounted sensors that are broken because technicians see a rubber snap-in valve stem and then assume there is no TPMS to worry about. The yellow dashboard light should have been the clue to take a closer look, but it's still easy to complain about missing it. It looks like Ford is basically stuck with the band-mounted disasters for at least the 2008 model year, but hopefully they will be phased out after that.

Sensor solutions

The newest solution to sensor fitment issues has been the snap-in sensor introduced by Schrader Electronics and included on a lot of General Motors Corp. vehicles. It features a two-piece design with a universal valve stem with a detachable sensor. This eliminates the need for grommet and seal kits, not to mention valve stem torque wrenches for the hex nuts.

The beveled brass edge below the threads for the valve cap is the sign there's a sensor under the valve stem. It's easy to install at the factory, easy to service in the field, and the valve stem can be replaced without throwing away a perfectly good sensor.

But none of that has anything to do with relearn and replacement procedures. That particular TPMS operational aspect is totally dependent on the vehicle. Since 2005, most Chrysler and Dodge vehicles have featured automatic relearn under any circumstances. After rotating the tires, the light will stay on for a few minutes and then it will go out. Replace or repair the tires and you'll get the same result. Replacing the sensor is no different.

In reality, if the technician can avoid breaking the sensor during the demount and mount process, the vehicle will handle the rest after it's been driven for 10 minutes above 25 mph. The simple fact is they've made a business decision to spend the extra money for these features.


Everything ultimately comes down to money, so the re-introduction of the next generation of indirect systems will be interesting to watch.

You read that correctly: The latest version of indirect technology can fulfill the requirements of finding four equally under-inflated tires and will be featured on some of the new Audi A6 models.

Over the last few years, I've been somewhat critical of indirect TPMS technology simply because it couldn't fulfill the requirements. It wasn't personal, it's just that I failed to see the point in discussing anything that was obsolete and would eventually go away. Again, I looked at the past to attempt to gain some insight about the future.

Presently, the indirect TPMS that is compliant with federal regulations uses the tire as a sensor. In the case of the Audi A6, more than 50 different sets of tires were tested in snow, ice, rain, high temperatures, low temperatures, mountains, prairies, asphalt, concrete, etc. They also had to account for every type of available engine and suspension system, not to mention the various rubber compounds, sidewall heights and belt constructions in the 50 different sets of tires.

All of this information is then used to create a computer program that enables the wheel speed input from each tire to be compared and contrasted in order to find an under-inflated tire. I'm positive that I make it appear to be much easier than it actually is from an engineering perspective, but that's the basic principle as I understand it.

The major selling point for this technology is that the hardware is basically in place to implement it with little extra cost. With a different ECU for the ABS, the TPMS will be A-OK. There is no relearn procedure, no sensors to break, no batteries to die, no valve cores to seize, and no extra time or tools for the technician.

When I first learned about this new technology earlier this year, I thought it was the greatest thing since tubeless radial tires if the vehicle manufacturers would embrace it. All of the problems associated with the direct TPMS would vanish overnight and the industry could get back to selling tires.

So I conveyed my theory to someone who knows a thing or two about TPMS at the vehicle manufacturing level, the lead engineer for chassis electronics at GM, John Maxgay.

Maxgay has been a tremendous ally for the aftermarket when it comes to servicing the TPMS and he will once again take the time to come to Las Vegas this fall for Tires at Two during the SEMA (Specialty Equipment Market Association) Show and the Performance Tires & Wheels segment to share his knowledge and experience.


As it is my style, I point-blank asked him if GM was considering the new indirect TPMS. His official reply was, "Our minds are always open to new technologies that do the right thing for our customers."

So the question becomes whether or not the new indirect TPMS is the "right thing" for General Motors, and there is no answer at this time.

Even if every new vehicle manufacturer were to immediately embrace the compliant indirect TPMS technology, it would still be years before it actually hits the streets and is seen in the bays of a tire dealership.

Between now and then, there still will be millions of vehicles with different valve stem or band-mounted sensors that will have enough relearn and reprogramming procedures to make it nearly impossible to service the tires without the proper resources and tools.

Since there is no indication that anyone other than Audi is currently implementing the new and improved indirect TPMS, my guess is that it will be a long time before we see it on a regular basis.

Judging from what I've seen and heard over the last few years, it's my opinion that direct systems will dominate the market for at least the next decade. But change is a constant denominator with TPMS technology, so I wouldn't be surprised if indirect made a comeback. I'm just not betting on it right now.

You and the BBB: Dealing with the imperfect world of tire pressure monitoring

I am hearing a lot of complaints from consumers because tire dealers are not able to turn off the tire pressure monitoring system (TPMS) light on the dashboard when a sensor is replaced on some new Toyotas. One person actually went to the trouble of filing a claim with the Better Business Bureau (BBB) because "if the tire dealer broke it, then the tire dealer should be able to fix it."

In a perfect world, that would make perfect sense. But the TPMS planet is far from perfect, so when a technician breaks a sensor on a late-model Toyota, the car will have to be returned to the new car dealer so the new sensor can be programmed into the vehicle. Those facts cannot be avoided. But the BBB still has the complaint on record for that tire dealer, and the dealer was not technically wrong. This is what happens when the dealer doesn't take the time to educate the consumer and explain the situation. The position of "it's not my problem" will only lead to more BBB complaints about the tire industry and TPMS technology. - Kevin Rohlwing


TPMS service tips: Be cautious rather than careless

Tire pressure monitoring system (TPMS) inflation sensors/transmitters generally cost in the area of $50 to $150 each, depending on the application. In most cases, if a problem does occur with system operation and recalibration efforts are not successful, the cause may be a damaged or failed sensor.

Exercise care during tire demounting to avoid sensor damage. In other words, don't blindly position the tire on the machine. For tires with valve stem sensors, the valve stem is positioned at the demount/mount head for demounting and opposite the head for mounting.

Since the band-mounted sensor is located inside the tire and hidden from exterior view, it is very possible to unknowingly damage a sensor during tire demounting. Therefore, when breaking the beads, do not use a full stroke of the shovel because the sensor could be anywhere in the drop center of the rim. Once the band-mounted sensor position has been identified, the tire can be safely demounted.

* When replacing a damaged sensor, you may have to note the ID number on the new sensor for certain models. The number may be required for input when initiating or re-setting the system. In these cases, remember to write the number on a piece of paper before mounting the tire.

* Pay strict attention to torque specifications with regard to installing a clamp-in valve stem sensor. Over-tightening can damage the sensor.

* Some tire pressure monitoring systems will share the keyless entry's receiver. This means that the remote key fob may be needed for specific procedures.

* Don't replace wheel sensor parts haphazardly. Some sensors feature aluminum caps and nickel-plated cores. The end of the valve stem may serve as the sensor's antenna. Only replace cores or caps with the correct originals.

This article is part of a regular series written exclusively for Modern Tire Dealer by Kevin Rohlwing, senior vice president of training for the Tire Industry Association. He can be reached at (800) 876-8372, ext. 110.

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