Re: Tire Monitoring System

[MSV96 <MSV96@aol.com>]

In a message dated 12/17/97 Jim Dupree <dupree@alldata.com> writes:

<<I think it is a neat idea but I can live without it. I see it as helpful
for someone that does not check the tire pressures regularly and is not
likely to stop if it "feels odd". I can usually feel the difference if a
tire is low (significantly low) and I will stop and do something about
it.>>

Agreed...to a point. I think your "can usualy feel" is key cuz this implies
that sometimes maybe you can't. No flames intended...read on :)

With the ultra high performance rubber now available sidewalls are VERY stiff.
Unless you use a gauge or run the car up near the limit you may not notice. As
is the case with "runflat" technology it is very difficult to feel pressure
changes when not pushing the car (and tires). 

My personal case in point was with my 5ktqwagon which had VR Gatorbacks (back
when they were available in our size) and was picked up at the airport by a
friend in my car. Apparently while on vacation a slow leak had taken one of my
tires down to about 15psi...VERY low!!!! My friend drove over Hwy 17 from
Santa Cruz (a fast but twisty state highway) to pick me up and on the drive
home I noticed the handling wasn't quite right (he didn't detect a problem at
all...adnoh drivers ya know?). The feeling was very subtle since I was well
under the limits of the car (under normal inflation conditions of course). At
80 in a straight line the car felt perfectly normal...only when turning in did
I notice things felt a little funny (this after 10 days driving some rental
car). Upon returning home the tire did NOT appear low visualy...but sure
enough upon checking (I use a dial type gauge) it was about 20psi low. Since
then I have never trusted my eyes, only a good quality pressure gauge...every
time I get fuel. Stiff sidewalls can fool you...this is why the sensors will
be required with "runflat" tires. Flame me all you want for my not being a
"sensitive driver" but that was my experience.

My recollection of the reasons for this sensor techonology in the 959 was the
same...in a straight line one may not notice deflation until the next high
speed turn-oops too late. I also have seen the same thing occur in motorsports
countless times (cut tire...driver unaware untill it's too late...car goes off
at the next corner) so I know that it can happen to the best of us in the most
highly tuned of cars.

Without "runflat" the sensors are not a bad idea. My understanding is that
with "runflat" they become essential. My only objection today would be cost
knowing that like all relatively new technologies the price will plummet when
the volume goes up.

<<A friend of mine just had this set up installed on his F-40. This is
probable a good application since he does not drive the car regularly
but drives it hard and fast often enough.>>

An even better reason is no room for a spare along with wheels that are
different sizes which makes a spare tire not an option. According to the
artice I read on this, the new 'vette and prowler both use this technology
because neither of those cars have a spare...

Mike Veglia
87 5kcstq