I'm one of the 2004 owners you envy, but this doesn't make any sense to
me, either.  I've always heard that the higher the pressure the better
the fuel efficiency, at the tradeoff of a harder ride.  Meanwhile, if I
recall correctly, my owners manual calls for 35 PSI for the front tires,
32 PSI for the rear, and that is distinctly _not_ soft.

What you're describing is unusually rapid wear. Questions to be asked of an
owner experiencing such wear would be:

Are you maintaining the recommended tire pressure? Another message mentions
32 rear and 35 front p.s.i. Personally, I keep it simple and run 35
all-around.

Are you rotating and balancing your tires at 5000 miles with your oil
service? Although many cars don't need that frequent an interval for
rotation, the Prius is notoriously heavy in the a.s (J-Lo effect from all
the batteries, no doubt.)

Finally, are you an extreme driver? Do you rapidly accelerate, decelerate,
high-g turns, etc? Do you haul alot of excess weight? Five heavy passengers?
Bunch of cargo?

As a last resort, try going to another tire dealer and see what they have in
catalog for high-efficiency tires in that size. Your dealership may be
selling you a softer compound tire. If you look at the sidewall you'll see a
wear rating (three digit number.) I've seen dealership tires with 360 wear
ratings (my Chrysler Concorde comes to mind.) Wear ratings can roughly be
translated to miles by multiplying the number by 100. A 600 rating is a good
long-life tire.

KK

US 2001-2003 OEM Prius tire:
Bridgestone Potenza RE92 XL (Extra Load)
P175/65 R14
84S
Treadwear 160
Temperature A
Traction A
50psi max. cold pressure

US/Canada 2004-? OEM Prius tire:
Goodyear Integrity (Standard Load)
P185/65 R15
86S
Treadwear 460
Traction A
Temperature B
44psi max. cold pressure

note the low 160 treadwear rating on the 2001-2003 "Classic" Prius
tires.  Although Bridgestone warrantees them for 40,000 miles, most
owners seem to get about 20,000 miles out of them, some up to 40,000
miles, some as low as 5,000 miles.  So, your 20,000 miles on a set is
about average.

First thing to remember is to keep an eye on tire pressure.  Toyota
recommends 35psi front, 33psi rear.  However, many Classic owners have
experienced rapid edge wear, leading them to up their tire pressure.
Anything up to the max cold pressure on the sidewall is fine, but the
common choice seems to be around 42/40 or 40/38 or thereabouts.

Remember to keep the +2psi bias on the front tires.  I tried going to
40psi all around once on my 2001 Prius - any time I had to do a panic
stop (my commute had lots of Dunkin Donuts shops on the way -
uncaffinated people suddenly stopping for coffee without signaling and
such - grr!)  and any time I panic stopped the car felt like it wanted
to fishtail (back come around the front).  I changed to 40psi rear,
38psi front, and the car just stuck and held in place when doing the
same stop.  personally, I like a +2.5 to +3psi bias in the front for
stopping characteristics.

Also, what type of roads are you driving on?

Do you often turn your tires when your car is not moving (scrubbing the
tires on the pavement)?

How quickly to you take turns?  (I find myself taking turns far too
quickly in my Prius, as I don't really notice the speed...)

Have you had your alignment checked?  If you're getting the average
20,000 miles on the OEM tires, then it's probably OK, but if you're
getting far less than that it's usually the alignment...

All can lead to higher tire wear.

There are alternate tires out there that you can investigate, which
have a higher treadwear rating (longer life).  Your Toyota dealer will
only tell you about the OEM tires, but as long as you keep the same
load rating or better than the OEM tires,  you should be fine.  For
some suggestions, see:
http://john1701a.com/prius/prius-tires_classic.htm

BTW:  you'll find far more Prius owners over at:
http://autos.groups.yahoo.com/group/toyota-prius/
http://www.priusonline.com/
http://www.priuschat.com/
and for the 2004+ Prius:  http://autos.groups.yahoo.com/group/Prius-2G/

It was a well known problem with premature wear on the Potenzas that cam
e with the 2001. The ones on my 2001 lasted less than 15000 miles,
including a blowout on one. I replaced them with warehouse club
Michelins, which still looked good when I sold the car with 60000 miles
and I still got 50mpg overall. Many others were able to get a free set
of tires from the dealer when they first showed excessive wear. In
retrospect, that is what I should have done. I'm happy with the
Goodyears that are OEM on my 2004 Prius. 8000 miles and no obvious signs
of excessive wear.

Bill