"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?

Jeff

--
Jeffry Wisnia

Jeff

I wonder if it would be legit to consider the distance from the axel
center to the pavement becomes smaller when the tire is underinflated. The
tire is free to flex and scrub as it wishes. The important parameter would
be the "rolling radius", wouldnt it??
The picture gets pretty clear if you'd allow the underinflated tire to get
thrown off. Then it would really have to turn alot faster to keep up with
the other wheel with the good tire.

Jerry