"Jeff Wisnia" wrote in message
...

The "NPR "Car Talk" show's "Puzzler" a couple of weeks ago gave an
answer stating that some car's computer "knew" a front tire was low on
air because the ABS system noted that wheel was rotating "a heck of a
lot faster" than the other wheels when the car was driven.

I didn't buy that one.

Sure, the rolling radius of a low tire is less than that of a fully
inflated one, but the overall circumference, particularly on a steel
belted tire, remains the same. Barring slippage, that circumference must
lay its whole length on the road once per revolution, just like the
circumference of a full tire does.

From my TSD rallying days I remember that low tire pressures made some
slight differences in odometer measurements, but these were in the
second decimal place, hardly "a heck of a lot".

Am I missing something here? What do the great minds on rcm think about
this one?



I'm not sure if this applies but on the newer Chrysler products they have a
tire pressure monitoring system that works by having a transponder located
in the valve stem. There is a sensor located in the fender.

If you are not familiar with transponders, they are common in several
applications like injectable little pellets for dogs and cats that can be
scanned to help a lost pet.

Newer cars also have them molded into the head of the key. if an
unauthorized duplicate is made or the lock is forced the car will not start.

Perhaps the car in question had a tire pressure monitoring system.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.