Tire Pressure

It depends on what you want (balance between comfortable ride and gas mileage).

My car came at 35 PSI all the way around. I'm running 44 psi in the fronts and 42 psi in the rear (max PSI = 44 for my tires). I did this within the first 3 days of owning the car, so I haven't noticed a difference (because I don't have anything to compare it to). I ran my Integra at max PSI for over a year with no noticeable wearing at the center of the tires (a common fear that "overinflating" your tire might do).

Some of the more "rabid" hypermilers will run their PSI much higher 50, 60, 70 psi or more, but there is diminishing returns on rolling resistance.

 

I have the Yokohama tires and my max tire pressure is 44 psi. I now run mine at 42 front and 40 rear.

I was used to running tires around 36/34 so I took mine up in a couple of steps in order to get used to the harder tires. It did not take long at all to get used to this.

 

I ran 40/38 for 6 months and felt every crack in the road. Got maybe 1 MPG more that way. I am currently at 37.5/35.5 and enjoy the better ride.

 

Tire pressure is "subjective", to each his own. I had very little experience in my Gen III (at probably 34psi, from the dealer). Before taking our first trip several days after taking delivery, (beginning of Dec.) I hiked the tire pressure to 40psi, all around. The car has a firm ride anyway..... what's a little more firmness, especially if your someone like myself, who drives watching for rough road surfaces, (as well as other hazards), and ready to "dodge" them at a moments notice. With the cars tires so firm, I don't go looking for "chug-holes! It was a "trial",... months later they are still at 40psi.

 

I'm sure some guy with an excel here has tracked the MPG against PSI somewhere?

We have 800 miles on our car now. Initially we were dead on about 47.9 MPG when my wife would drive and I would bring it up substantially when I'd drive (at least 5 mpg better).

Anyway, at 40 miles this past weekend she was at 47.9. I drove another 8 miles and brought it up to 49. I then bumped the pressure from what it was at (very close to spec of 35/33). I took it to 42/40 and at 130 miles on the same trip my wife is now reporting--with her driving--51 mpg. Weather and driving patterns unchanged, as far as I can tell. Variables do change, though, but it seems like her bump in mpg was 3-4 miles/gallon. Seems optimistic; I'd not have expected it to go up that much so I wonder who's got numbers over more hundreds of miles in case this was just a one-off.

 

I think I saw more effect from higher pressures in colder temps, i.e.: the mpg gain may be greater in colder temps. Also depends on the tires themselves.

 

THE stock tire doesn't exist. One member bought 2 cars at the same time & got different tires. I don't know if there is more than one brand of 17" tire delivered on the V's.

 

Could we also hear some suggestions for a good quality/accurate tire gauge for setting our pressures.

Thanks

 

One way (with any car) is to check the driver's door sticker for recommended pressures. Mine came with the Bridgestones, but after they wear out, will probably go back to my favorite tires, Michelins. As far as pressure goes, the door says 35 psi for fronts and 32 psi for rears. There's always a trade off on going below or above recommendations. Higher pressure = harder ride but better efficiency. Lower pressure = more comfy ride but lower MPG. Add to that, if you go higher, you tend to get "middle tread wear"; going lower and you get "outer tread wear". I tend to go with recommended pressures.

 

The best tire gauge is one that you use regularly. So, I use a small one that I got at Advance Auto Parts for $1.99 which has a magnet on it and thus sticks inside the fuel filler door. When I gas up it reminds me to check the tire pressures and I do, once in a while, besides, it is always readily available when I want it.

I checked it against a very expensive digital gauge that I have and it was within a pound every time.

Spending a lot of money on a tire gauge is a waste of money, in my opinion, but I do like to have nice things too.

 

I've been using an Accu-Gage dial gauge for decades--see below (I have the swivel angle gauge, 60 PSI max, with a rubber gauge guard. Very durable and accurate, and reasonably priced:

Dial Tire gauges

I also have the "chek-a-spare" hose connected to my spare and ran it to the left side storage area for easy checking of the spare tire pressure:
Chek-a-spare, Check-a-spare, tire gauge guard

 

Responding to both questions based on other threads I recently found on this site (looking for exactly the same info): Just last night I increased tire pressure on my brand new 2010 Prius II to 42F,40R. I did this using an Accu-Gage H Series 60 psi pressure gauge ordered on Friday and delivered yesterday from getagauge.com (highly recommended by numerous PriusChat contributors). Too early to tell whether it make a difference in overall MPG compared w/ pressure as provided by the dealer - but I am optimistic/hopeful. Also, I didn't bother with nitrogen.

 

Don't EVER pay for nitrogen.

Natural ambient air on earth is 78% nitrogen already.

Once I was being a smart nice person and told the guy at pep boys I wanted 3 quarters nitrogen and a quarter of pure oxygen.

The got him trying to sell the nitrogen when I noticed that he really thought the air we breath was 100% oxygen.

I guess its not that common of a scientific fact.

 

There is a whole thread for this, with at least 3 models of 15" and 3 models of 17" appearing within the US, and more models in other markets: What tires did you get on your 2010?

 

When the tire guys here rotate the tires they seem to set the pressure to 32-35PSI. I then refill them to 42-44PSI and believe that the higher pressure gives me about 4-5 MPG better mileage without really compromising the ride. Of course the driving conditions are never exactly the same, so I can't say for sure that I get 4-5 MPG better, but that seems to be the case.