Anything concerning tires

10 responses total.

Has anyone used Accu-Pressure tire pressure monitors (run the name on
Google if you don't know what these are)? If yes, what is your experience
with them? 

Most of the web sites I looked at have calculators for tire pressures for
different makes, models and years of cars. However these come up with
values that don't agree with the stickers in our cars. What's the real
poop on tire inflation? I'm sure there is considerable leeway.

Those calculators also just give suggested pressures, not which rating
of A-P monitor they recommend. What would you suggest?

The monitors just screw on in place of a valve cap - and are as easily
removed. I would expect theft. One vendor in England also sells "Locking
Kits" for the monitors, which consist of nuts that fit on the valve stem
thread and a small wrench to put on your key ring. You put the nut on
first and back-tighten it after installing the monitor. Is that effective
to prevent just hand removal of the monitors? 

In that connection, what is the thread size of valve stems?

The Accu-Pressure caps look neat, and I considered using them once.  I
was concerned about creating a slow leak, though.  To measure the
pressure, they push down the valve stem, so the cap becomes your only
air seal.  They also don't indicate red until you get 10 psi low, and I
find a 10 psi drop is visible just by comparing the low tire to the
other tires on the car.

The tire pressure on the sticker on your car is the car manufacturer's
recommendation.  It's a compromise between ride quality, handling, and
fuel economy -- on most cars I've had, it was pretty low, to make the
ride smoother.  On some cars I've found a higher pressure improved
handling and fuel economy.  It's partly a matter of taste.  I
experimented with my Honda, for example, and found that running
front/rear pressures of 35/29 gave more balanced handling and better
tracking than the 29/29 that Honda recommended.  Incidentally, the
weight rating on the tire is only valid at the tire's maximum inflation
pressure.

I still haven't figured out the best pressure for my Volvo.  Right now
I'm running the door sticker pressure, but that was written for 185R14
tires, and I have 195/75R14s on it.

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Checking your tire pressure frequently is a lot of wasted time and effort
most of the time. You should only check your tire pressures when they need
to be checked. That is what Accu-Pressure monitors would let you do.

There is another device, a tire pressure transmitter, that is put inside
the tire and reports the pressure. These are currently rather expensive
devices, but if built into wheels and cars, they would add relatively
little to the cost of a car. I am actually surprised these are not yet as
standard as other instrument gauges. 

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Reread my #4, tod. I suggest you should check your tire pressure when
it needs to be checked. Didn't you  notice the tongue firmly in cheek?

Yes, but the Accu-Pressure monitors don't tell you anything until the
tire is already 10 psi low.  That's a pretty dramatic drop, and I can
usually spot that visually by comparing the suspect tire to the other
one on the same axle.  They're a neat idea, but they aren't sensitive
enough and by defeating the tire's primary air seal it seems to me like
they're more likely to cause problems than avoid them.

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Yes....sigh....

Re #7: they say they show "yellow" at 4 psi under, and "red" at 10 under.

Ah, okay.  I missed the part about them having a yellow band.

4 psi is a good limit.  I withdraw most of my criticism. :>

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