What tire pressure are you running at?

Why higher pressure in the rear? Most of the weight is on the front.

SCH-I535

 

Good eye. I didn't realize I wrote it backwards; I have 42 in the front.

 

Accurate what? Recommended tire pressures are never maximum pressure; and the pressues to use depends on the service to be used.
Maxiumum pressures are set by the tire manufacturer and recommended by the car manufacturer. Most car recommendations are based on comfort, not performance.

 

Higher rear pressure assists oversteer; when done correctly the handling gets more neutral. Its not that useful however for the C. Reducing understeer is much more useful.

 

Umm. What are you trying to argue? I didn't make an incorrect statement. I was pointing out that Max tire pressure is not specific to a car. Instead it is specific to the tire and the Prius c comes with a few different tire options then, now and will in the future.

 

While it seems the higher tire pressure most certainly improves gas mileage I must wonder about how the increased tire pressure may increase stopping distance, especially in wet conditions?
I also must be suspect about how handing may be affected by the higher pressures.
Although anectodal comments are handy and everyone loves to read them only a scientific test can provide this type info.
It seems to me that Toyota has probably already spent massive amounts of money doing such tests and if these higher pressures could safely improve gas mileage then Toyota would recommend the higher pressures
So to summarize I feel like the factory tire pressure recommendations may not provide the best gas mileage but should provide the best traction available in the various driving conditions that the vehicle may encounter during a typical trip.

 

In the tests I have read, journal papers, the increase in air pressure decreased stopping distance on some surfaces. I can't remember what that surface was but in general the higher the pressure the more it negatively affected stopping distance. Low tire pressure obviously had a negative affect as well. The pressure used in testing were not very high either. I believe they were lower than 40psi.

Very high pressures can also have a negative affect on FE if the surface is very rough and you are traveling at high speeds. You essentially lose traction as the tires skip over small surface irregularities. As low speeds high pressure can have a very positive affect on FE and stopping distance is not as much of a concern.

 

I'd think Toyota's recommendation for tire pressure balances several variables. They would like the car to perform well in fuel economy tests, obviously. They're also thinking about ride feel, cornering stability, braking and so on.

One thing I'm thinking, raising pressures is going to put more stresses on your suspension, since the tires absorb less of the small road surface variations, instead transmit them up into the shocks and springs.

Also, lower profile tires are less forgiving at higher pressures: I keep our OEM 215/45R17's closer to recommended pressure (though still a bit higher), then our snow tires in 195/65R15.

Bottom line, play with the range between the Toyota recommendation and the max pressure indicated on the tire sidewall, decide what works for you.

 

40F and 42R here

 

44 on all 4,,, btw go check your spare ~ mine was underinflated,,, and you need to remove it to test it. the valve is on the other side facing the rear tire well. oy vey,,, anyway i put 44 on all 4. i get much better responsive handling.

 

36/34. For the better ride. Averaging 60 mpg on 40 mile daily commute in warm weather. 1/2 highway, 1/2 not

 

38 all around.

 

I run at the pressures on the door frame placard... basically as I am in full agreement with comments made by F8L and Mendel above.

Roland

 

40 front and rear.
Had to use donut 10 days back and found it was at 40 psi whereas recommend inflation pressure was 60 psi. Had pump but unpleasant to inflate on dusty gravel road in wilderness with passing vehicles. Recommend you carry pump and check donut psi before trip.

 

Michelin Defenders
42F/40R

I normally drive in Eco mode.

Before my last tire rotation (free at Mavis) I decided to check my spare tire pressure. It was only 26 psi, instead of the recommended 60 psi. Yikes!!! I'll be sure to check it more often now... Unfortunately you have to physically remove the spare in order to access the valve stem, a real (well, moderate) pain in the a**.

 

I checked our spare soon after purchase, and of course it was at 40 psi.

 

Does anyone have good solid, scientific evidence that of whether higher pressures make it more or less likely to have blowouts on rough, potholed gravel roads?
If no good evidence, does anyone have a good reasoned argument one way or there other?
If no good reasoned argument, does anyone have completely uninformed, anecdotal, hearsay evidence one way or the other?

In the third category: I had my OEM Avids at 40 psi when one blew out on the Top Of The World highway in the Yukon, but I could also have simply been driving too fast for the conditions.
I asked the bus drivers in Denali National Park, and they said the tires on their fleet of busses are under inflated by 10 psi from the normal specified pressures to help cope with the rough, gravel road they drive for about 8 hours every day. However, that underinflation may have been for better grip on the gravel and thus to avoid sliding down the mountainside rather than to avoid blowouts--he was not certain.

 

I had mine at 42/40 but for my 50 mile one way commute I was just getting beat up on these California roads. I have to go with comfort on this one, 35/33 does give a better ride.

 

40/F
40/R
Almost 50,000 miles