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gpsman1 · #23 (**permalink**) 01-05-2007, 12:59 PM

Again, not comparing apples to apples.
The system of using ABS to "indirectly" measure tire pressure status will only tell you when there is a gross change in tire shape. The only thing this method is good for is telling you when your tire is FLAT. And if you need a sensor for that, then you are an idiot.

The tire circumference on modern passenger tires changes by less than 1mm ( out of more than 2000mm ) at any pressures between 10psi and 60psi. So in theory, the tire size changes. In reality, the change is too small to measure, or to have any mentionable effect on speedometers or odometers. I didn't know you guys wanted to talk "microns". If that's the case, then the length of your vehicle changes with speed also, as Einstein predicted, as the atoms get spread out by 0.00000000000000001mm when you travel fast... Geez... can we come back to what actually matters now?

Again, don't take my word for it. GO OUT AND MEASURE!
-John

Quote:

Originally Posted by Thegreatescape

If this is indeed true, then how do many manufacturers (including some Ford models) utilize the ABS sensors instead of actual air pressure sensors to operate their TPMS systems?

For example, this was taken from from the 2002 Windstar shop manual section 204-04:

"The Low Tire Warning (LTW) system detects differences in inflation pressures in one or more tires. The system uses the ABS wheel speed sensors to monitor the rolling radius of the wheel and tire assemblies."

A few other vehicles that use this approach include 2001 to 2003 Ford Windstar, 1997-2002 Buick Park Avenue, 1999-2003 Buick Century & Regal, 2002-2003 Buick LeSabre, 2003 Buick Rendezvous & Aztek, 2000-2003 Chevy Impala & Monte Carlo, 1999-2002 Chevy Alero, 1999-2002 Pontiac Grand Am, 1997 - 2003 Pontiac Grand Prix, 2000 - 2003 Pontiac Bonneville, and 2001-2003 Oldsmobile Aurora. Source: http://www.aa1car.com/library/tire_monitors.htm