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Stupid tire store conversation about air pressure

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Posted by Mike Rosenberg on September 2, 2006, 8:23 pm

Everyone in the Prius community who reads this newsgroup or any of the
mailing lists and web forums knows about increasing your tire pressure
to increase mileage.  Hell, I'd heard about and been doing that for
years on my previous cars, too, just not to as high a degree as now.

Yesterday I had a flat tire, took it to a tire store to be repaired
(ended up needing it replaced, but that's another story).  The manager I
dealt with asked if I was aware that my other tires were at 40+ psi, and
I told him yes, that it was intentional for better mileage.  He
understood and even explained how it works to another customer who was
standing nearby, after telling the mechanic to reinflate the tires as I
had them.

Well, the mechanic came out front a minute later and "explained" that
the tires are only rated for 35 psi and that overinflating them would
cause the sidewalls to give out.  I said okay and drove off, then of
course inflated them to 42 front/40 rear on my own as I'm accustomed to
doing anyway since the Toyota dealership never gets it right.  It just
gets me that this guy would say something like this when, right on the
tires, in raised lettering, it says the maximum pressure is 44 psi.

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Posted by =?iso-8859-1?Q?mark=5Fdigital= on September 3, 2006, 10:04 am

I don't understand why you would want to sacrifice comfort and stability by
increasing the tire pressure beyond the recommended amount for the car
itself. And as for the tires being rated for 35 psi I'm sure he really meant
the car not the tires.
When you over inflate the tires ground clearance increases too so it's
questionable whether you gain mpg. Air resistance might offset the less
rolling resistance. Ultimately all you may have gained is a rough hard ride
and premature weakening of the front end.

Posted by Michelle Steiner on September 3, 2006, 1:28 pm

Because it doesn't sacrifice comfort or stability.  Experience shows

It may be questionable--everything is questionable--but it does gain
mpg.  Experience shows this.

Stop Mad Cowboy Disease:  Impeach the son of a Bush.

Posted by Mike Rosenberg on September 3, 2006, 1:34 pm

If I didn't feel the ride was comfortable, and especially if the car was
less stable, I wouldn't keep the tires at 42/40, but my ride is
perfectly comfortable and stable that way.

Oh no, he absolutely meant the tires when he talked about their
sidewalls not be able to handle anything above 35 psi.

This isn't something I've just made up, and it's not just common
knowledge in the Prius newsgroups, mailing lists and forums, it's
something I've read about for years.  Increasing tire pressure up to
near the maximum rating increases fuel efficiency.

I don't have a rough hard ride.

Never had any problems in my previous cars.

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Posted by Kubalister on September 3, 2006, 2:17 pm

mark_digital© wrote:

What have you been smoking????
Cars themselves do not have a maximum tire pressure, they only have a
maximum recommended wheel/tire dimension. The pressure limit is set by
the tire manufacturer to keep it within the required dimensions and
physical stress limits of the material used.
For your interest the Prius is shipped everywhere else in the world
outside of the U.S. with Michellin Energy tires which have a maximum
pressure of 51 psi which many drivers use (and the ride is NOT
noticeably rough at that pressure).

With that statement you obviously DON'T have any experience in inflating
the tires to higher levels on the Prius. If you did you would KNOW that
it DOES improve mileage performance.

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