tire pressure

[fhenry55]

the max tire pressure for the tires that came with the prius is 44psi. i read the 42/40 is what alot are using. my question is what happens in the summer when psi seems to expand?

[bbald123]

Originally Posted by fhenry55

the max tire pressure for the tires that came with the prius is 44psi. i read the 42/40 is what alot are using. my question is what happens in the summer when psi seems to expand?

Tires tend to lose pressure over time.

Correcting for temp fluctuations is one of the reasons for checking your tire pressures frequently.

[Bob64]

tires also tend to lose pressure when punctured by a road hazard, such as a nail.

Oh, and 44psi is not close to the "max" pressure. Imagine what would happen if we hit a bump. The bursting pressures is probably over 90psi.

[diamondlarry]

Originally Posted by Bob64

tires also tend to lose pressure when punctured by a road hazard, such as a nail.

Oh, and 44psi is not close to the "max" pressure. Imagine what would happen if we hit a bump. The bursting pressures is probably over 90psi.

It's actually somewhere north of 200 psi. I have a friend who has a connection to someone in the tire industry who has done max pressure tests and it's way over 200 psi. For obvious legal reasons he doesn't want the the brand or the exact pressure revealed in case some idiot would go out and try running a couple hundred psi in a tire and get hurt or killed.

[john1701a]

I've been using 44/42 for many years now.

It's no big deal. In fact, it's down right impressive that tires nowadays wear so evenly with higher pressure.

Routine topping off is needed. They do soften over time.

.

[ksstathead]

Measure cold pressure (before driving). If temps warm alot in a short time and you don't want a couple extra psi, you would need to bleed a little. Don't bleed air after driving, because that expansion is built into the max number or other recommended pressure you wish to follow.

[diamondlarry]

The only time mine have been under 60 psi was when I left the dealer and went across the street and pumped them up just over 15K miles ago.

[ibmindless]

I've been running 42/40 PSI for the last 3000 miles. Before that, I ran 40/38. Now I have 8000 miles and the fronts have noticeable wear in the center of the tires --- just like you might expect from over-inflating. So... I just rotated the tires and went to 37/35 PSI.

I'll closely monitor MPGs, but if there is no significant loss in FE, I'll stay with the lower PSI setting.

[Boo]

Originally Posted by fhenry55

the max tire pressure for the tires that came with the prius is 44psi. i read the 42/40 is what alot are using. my question is what happens in the summer when psi seems to expand?

That's the maximum cold psi measurement (when the tire's psi is stable because it has not been run on for a while, e.g., 3 hours), whether in cold or hot weather.

Changes in the ambient temperature which cause a change in the tire's psi is one of the reasons why we're supposed to check our tires' psi regularly.

[Dan.]

Yep, got mine at 70psi, but I'm about as nutty as Larry .

Set it to 40 something. If you ever get nutty, pump it up to 70psi. The fun part is watching the mechanic check the pressure at arms length since he thinks the valve stem is gonna explode.

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