Eye on electronics

Motor,  Sep 2002  by Dale, Mike

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Other manufacturers have tried mounting the hardware externally, but this exposes it to various road debris, salt and other hazards. There has been concern voiced about what happens when someone uses one of those roadside tire-inflation products. Since most of the PSB systems are constructed as part of the tire valve, such a leak-stopping compound could clog the sensor. Another worry is tire removal and replacement. The guys in the tire shop will have to be very careful not to damage the PSB hardware when removing or installing tires on wheels.

As mentioned, there has been a lot of discussion over how good these systems need to be. A mandate that every new car needs a $200 tire pressure monitoring system will stir up a lot of opposition. As is normal with agencies like NHTSA, a preliminary ruling is issued as to what the requirements are going to be. Then they ask for comment from concerned parties before making the final decision. NHTSA got lots of comments on its first proposal that included a requirement that a driver had to be warned when any given tire was 25% or more underinflated.

The Rubber Manufacturers Association pointed out that a tire that's 25% underinflated might not be safe to drive on. The pressure requirement placed on the side of the tire is the minimum cold pressure needed to support the maximum safe load of the vehicle. The concern is that if a tire pressure monitoring system doesn't go off, a driver will think the tire is sufficiently inflated.

In the end, NHTSA issued its final ules in July 2002, and they're a compromise. Vehicle manufacturers have wo options-one, that the TPMS must warn the driver when the pressure in my single tire or combination of tires zas fallen more than 25%; or two, that the warning must be issued when any jingle tire falls 30% or more below the recommended cold inflation pressure.

So either system can be used over :he next three years of the phase-in. During this time, studies will be conduted and further system development will occur...one hopes. At the end of the three years, NHTSA will look at the tire pressure monitoring issue again and deide what the permanent long-term warning requirement is going to be.

The thing you want to remember and pass along to your customers is that tire pressure monitoring systems are going to trigger only when there's a major underinflation. The lost fuel economy, early wear-out of tires, loss of braking and handling performance and those sorts of things will not be prevented by these monitoring systems. Remind your customers that they still need to monitor the pressure in their tires.

Copyright Hearst Business Publishing Sep 2002
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