Tire pressure for 2014 Prius

1) I never exceed the rating on the tire itself.
2) I try to acheive even tread wear, this varies by tire but 41 to 38 psi is about right.
3) I inflate the rears about 2 psi less than fronts.

 

Being somewhat "old school", I'm willing to try added pressure, so I'm running 40/38 for our upcoming 6,500 mile trip. I'll be checking tread wear to see if it's making a difference across the width of all 4 tires. I tend to shy away from max pressure just because. I understand max pressure is a cold setting and all, but I'm just not ready to go that far when so much of my driving will be at highway speeds. FWIW, the tires came at 32 all around, so I was pretty disappointed with that. It should have been part of the dealer checklist before delivery and they should have at least been 35/33 like the door sticker says.

 

37 to 38 psi for mine...

 

42 at front, 40 rear. Been driving for 9 years with this tire pressure from 2005 through the Prius 2004, 2008, 2011 and PiP 2012 till today.

 

42 front/40 rear on a Prius v. Sidewall says 51 max. At 40,000 mi. no sign of uneven tire wear.

 

I'd be interested to see if anyone has documented proof that inflating tyres over the recommendations gives any benefit in fuel economy. I run mine at the recommended pressure, 2.5bar front, 2.3bar rear and am very happy (over the moon) with the economy I get.

 

There's plenty of documentation. For example: mythbusters tests tyre / tire pressure - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

 

There are some simplified equations you can use to see the general rolling resistance trends, I have posted before. Note that any specific tire would have its own characteristics. In other words, pay more attention to the shape of this plot, not the absolute numbers:


I've seen some posts in Google, the hypermiling guru Wayne Gerdes used extreme high pressures (55psig+) he liked that. But unless you are trying to set the world record for miles per tank on a Prius (which some here are trying to do) I don't think we should go over-board on it. Main thing is MPG drops fast at less than recommended pressure.

EDIT- The Mythbusters data gives a strange plot showing extreme benefit for going a few pounds over recommended. Something seems a little whacky in their data, but keep in mind each tire is unqiue.

One big variable is tire temperature, whereas higher tire temperature greatly reduces rolling resistance (yet another reason why we see lower MPG in winter). I don't recall if Mythbusters talked about warming up the tires for 15-minutes before their tests, but that's what they'd really need to do. My plot is after warm-up. My plot of course is not perfect either ...I think my plot is estimating what happens to rubber rolling resistance vs. pressure. But I have no way to predict tire deformation vs. pressure, so that's where my plot could be off.

 

I figure if you're pushing something, there's likely some wiggle room, but don't push it too far or you create new problems.

On that wavelength, I raise pressures, slightly, say 4 lbs above placard values.

 

45 front and 42 rear

I've driven with higher and lower PSI before. Depends on the brand/model of tire how it handles at lower/higher pressures but I prefer to be able to take a hard corner with less lean/roll and the high pressure helps (not as much as a suspension upgrade but still it's noticeable).

 

As Mendel just said, I too am still working with the pressures on our new 2013. The 17"s that are on our Prius have a maximum of 51 PSI, so I have plenty of room to experiment. Currently I am at 45F, 44R presently and the tires seem to be pretty firm, but not overly harsh. I initially started working with 36F35R as the tires were actually on the date of delivery. Placard says 34F, 33R IIRC. I checked the tires before we left with the new car, and sure enough make ready had overlooked the air pressure setting. I thought the car seemed to be sluggish the day before when I test drove it. The low air pressure caused additional rolling resistance. Haven't made a highway trip since raising the pressure, but around town they feel great. Not too bad on the bumpy parts either. I do realize the firmer the tires, the more the suspension will take up the jolts. You have to find a happy medium between comfort, economy, and maximum utilization of the LRR capabilities of those types of tires.

IMO, the biggest mistake folks make on the Prius is trying non LRR type tires. Yes, there are some poor LRR's out there, but there also some excellent ones out there. The brands and what have you have been discussed here on Prius Chat. One simply needs to decide what amount of money one want's to spend and then purchase the best tire they can for their beloved Prius.

Bottom line, don't push the envelope. Find what works best for you, then simply maintain the pressure on all four after that.

Regards,
Ron (dorunron)