mileage versus tire pressure

[drew]

ok i'm new to the group, but have used the search function (to no avail ) for about an hour trying to find others experience with, recommendations and some technical detail on a problem i have had and solved with my used 02 classic prius. it came from the dealer with new bridgestone tires set at 30-32 psi. our initial tank milage was 38 mpg here in nh in the winter. after complaining , the dealer checked out the whole car leaving the tire pressure at 32 psi. i said enough of this, raised it to 50 psi cold as allowed on the tires max pressure rating. my average mileage has gone up to 50 with no adverse effects in ride, handling etc. it also stays in stealth much easier and longer.

since tires generally fail from overheating due to underinflation, and very seldomly due you see a tire worn out in the center(a symptomm of overinflation), i've not been in the least concerned at running at the max recom psi. has anyone had experience running significantly over that

could anyone refer me to posts providing some detail on this .

[efusco]

Drew,
Welcome to the forum...there aren't many posts here about the 1st Generation Prius ('01-'03), but I know what you need baby!

http://john1701a.com/

Scroll to the bottom of the home page and click on "User Guide Classic". It should have lots of good info on ideal tire pressures and why you should do that...notice that there's a lot of other really great info in there too.

Then, go back and just enjoy John's web site. It is probably the single best source of Prius info on the web--or anywhere else for that matter. It combines lots of specific technical data with lots of practical, real-world if annecdotal information that every Prius owner should know.

Enjoy your car.

[bruceha_2000]

Originally posted by drew
raised it to 50 psi cold as allowed on the tires max pressure rating.

I think I would be a tad conservative trusting that your pressure guage is extremely accurate and that the tires, though spec'ed at 50 psi cold will REALLY be OK there. Could be the mfg sets the value low as compared to their "unsafe any higher" tests, 'just in case' but still :-)

[drew]

thanks for the info lead to john's site which i have been to and it is helpful, but i couldn't find the link you mentioned on the this sites home page and i was hoping to find more technical info on the classic prius from owners or former owners on this site.

if worse comes to worse i will do towing rolling resistance tests at various tire pressures.

one of the reasons i'm making this plea for increased tire pressures is the response from bruceha which immediately cautions me about my gauge (yeah i'm sure they all have inaccuracies, as likely to be high as low (maybe ther's a consumers report on this), and we're not talking about being anywhere near the pressure required to explode a tire (whatever that is). i was particularly pleased to find the bridgestone tires rated for 50 psi which allows for considerable improvement while remaining within the tire supplier's specs.

i'd like to find a source for real info (beyond the anecdotal although that is useful)on the reduction in rolling resistance, and hence increase in mileage with increased pressure . perhaps if we all tried it for the next tankful and reported back on a poll as i've submitted, we could do us all a favor.

people seem to be interested in spending quite a bit of additional money for a car that gets no better mileage than a geo metro or a 1980 diesel rabbit , when it would just be easier to pump up the tires to get a marked free improvement in mileage (on any car, i might add). (they also seem to be willing to spend a lot on synthetic oil for supposedly the same reason)

keep trying, i appreciate the feedback.

[efusco]

thanks for the info lead to john's site which i have been to and it is helpful, but i couldn't find the link you mentioned on the this sites home page and i was hoping to find more technical info on the classic prius from owners or former owners on this site.

Sorry to mislead you, the link I was talking about was at the bottom of John's Site, not here.

If you want to abreviate your search for information a bit, cruise over to the Prius Yahoo Group at http://autos.groups.yahoo.com/group/toyota-prius/. That's loaded with Prius owners who can go through the whole gory history of tires on the 1st Gen. Prius. They have some pretty solid data on ideal tire pressures to use. But, you'll find all you need in John's User Guide too (at the bottom of HIS home page).

[Jonnycat26]

I'm likely to be flamed for this, but whatever...

Folks, there's a reason the tires have recommended and maximum pressures. They recommend you stick with what they recommend. If the recommended pressure is 35, and max is 48, then you don't want to go straight to 48. 40, maybe. But inflating to max pressure is really not a wise move.

When you drive, the air inside the tires gets warmer and the pressure goes up. As the tire ages, it starts to wear down. It's inevitable. If you're running at the maximum pressure and not the recommended pressure you're going to reduce the life of the tires, pure and simple.

[efusco]

Direct link to John's Classic User's Guide:
http://john1701a.com/prius/prius-userguide_classic.htm

[Wolfman]

Originally posted by Jonnycat26
I'm likely to be flamed for this, but whatever...

Folks, there's a reason the tires have recommended and maximum pressures.  They recommend you stick with what they recommend.  If the recommended pressure is 35, and max is 48, then you don't want to go straight to 48.  40, maybe.  But inflating to max pressure is really not a wise move.

When you drive, the air inside the tires gets warmer and the pressure goes up.  As the tire ages, it starts to wear down.  It's inevitable.  If you're running at the maximum pressure and not the recommended pressure you're going to reduce the life of the tires, pure and simple.

What you are stating here is already considered when stating the maximum safe pressure of the tire by the mfr. Tire pressure is measured "cold." If the tire is inflated to the maximum safe rating mentioned on the sidewall, it will still safely handle the "hot" tire pressure.

[daniel]

Originally posted by drew
people seem to be interested in spending quite a bit of additional money for a car that gets no better mileage than a geo metro or a 1980 diesel rabbit

I think I am speaking for a lot of folks when I say that I did not buy this car for the improved mileage. The mileage is a great talking point and gives me bragging rights. But it is only one of a great many selling points on this car. To compare it to a rattle-trap Geo Metro, or a dirty diesel Rabbit is a joke.

[SpartanPrius]

What you are stating here is already considered when stating the maximum safe pressure of the tire by the mfr. Tire pressure is measured \"cold.\" If the tire is inflated to the maximum safe rating mentioned on the sidewall, it will still safely handle the \"hot\" tire pressure.

That is true, except the car's suspension was not designed to be optimal to that pressure. When you play at the edge like this, you must be aware of the compromises. Tire manufacturers provide a maximum cold pressure value for the specific tire, and NOT that tire's application to the Prius model. Things that are potentially lost by doing this are: tire life; wet or snow traction; and, general handling characteristics. Any deviations made from Toyota's recommendation needs to take all of this into consideration. Afterall, they have spent considerable effort coming up with recommended values. Tire sidewall flex is key to how a car grips the road and rides smoothly.