Tire Pressure does make a difference!

All 4 of my tires were somewhere around 32, I upped them all to 38, and we're averaging 50.1 on this tank around town so far. In the past my tanks have averaged 47.8, so i am getting a slight increase as well.

I think I may pump them up to the 40-38 like you did and see how that goes....

 

<div class='quotetop'>QUOTE(dulcimer @ Sep 4 2006, 07:58 AM) [snapback]313965[/snapback]</div>

According to the last poll the majority of us were running 42/40.

Here is the link to the poll.

http://priuschat.com/index.php?showtopic=2...e+pressure+poll

 

40/38. And I am happy with the ride, handling and mpg.

 

<div class='quotetop'>QUOTE(seasalsa @ Sep 4 2006, 12:02 PM) [snapback]314000[/snapback]</div>

I think that poll is a little extreme, to say the least, and you can't say what the majority of people are running at based on the answers. Except for the Toyota recommended pressure of 35/33, I think the LOWEST choice in the poll was 40 or 42. The highest was over 100 -- but thank goodness, nobody said they were doing that. At least one person said their tires were at 60psi all around.

 

I had my DH check my tires for me a couple weeks ago (hey, I'm over 6 mo. pregnant...I gotta make him do some stuff for me!) and they were previously at 35/33 so I had him 'up' the pressure to 40/38. I had been getting some 'low' mileage tanks at 46-47mpg (which I really had to try for) and since the pressure was increased I've easily been getting 48-50mpg tanks. So I think tire pressure really does make a difference. I may eventually go the PC-recommended pressure route and get them up to 42/40 but I'm happy with the current pressure as is.

 

Yes, higher pressures do make a difference. You will have more rattles and the suspension will wear down sooner.

Other forum members have found no significant difference between the factory recommended pressure and overinflated tires.

 

<div class='quotetop'>QUOTE(jamarimutt @ Sep 4 2006, 12:33 PM) [snapback]314103[/snapback]</div>

Have you seen the max pressure on the sidewall? It's 44 cold psi. How do you see 42/40 as overinflation?? Let's see...am I going to take a car maker's word for what tire inflation should be, or should I maybe possibly perhaps be guided by what the actual manufacturer of the tire says? Wow, that's a real poser, that one....

Bear in mind that Toyota recommended 35/33 on the Classic Prius, and that was with Bridgestone Potenzas that had a 50 psi rating. I believe that after MANY complaints of premature wear due to underinflation (and replacements of prematurely worn tires) they quietly issued a TSB to their dealers that jacked the "recommended" pressure to something like 42/40.

Still think Toyota has better judgement?

 

I noticed the same thing. With my aftermarket tires they were set up at 38psi and I seemed to have taken a hit over stock rims/tires. By airing them up to 46/44 (tire is max of 50) I have recovered the mpg loss. Next time I'll buy lighter tires and maybe even get better than stock. Maybe lol

 

Are the people running 44/42 the same ones that are complaining about the handling and ride of the stock tyres?

My car on my local roads is awful at those pressures. Noisier, harsh, rattley and skittish over bumps. Doesn't feel remotely safe to me when the car wanders going round slow bumpy corners in the dry!

 

There are other variables that will affect your mileage from one tank to the next besides tire pressure. In other words, data on just one tank after changing the pressure may not be conclusive. I have kept my tire pressure constant since I got the car in March (weekly checks or better), and my MPG varies from tank to tank--sometimes to a surprising degree. Temperature, average speed and terrain seem to be the biggest factors...temperature also affects the gas tank bladder volume, which can have an effect on calculated MPG by changing the fill volume slightly from one fill-up to the next, and it determines how heavily A/C is used.

Although tire pressure is known to affect MPG, I am skeptical that it has that great an effect. The problem is that any data used to prove or disprove the hypothesis must also include all the other factors in order to single out the effect of tire pressure. I'd love to see that data, but life's too short.

- Doug

 

it's long since been established in this forum, and i've been lurking here since way back in '03, that 42/40 is the most common and best tire pressure for improving mpg. (if you don't mind a little bumpy ride) B) then again, of course terrain, trip duration, driving style, temperature also affect mpg....

 

tire breakin also makes a difference

 

Sorry - what does the dual number mean (e.g. 40/38)?

 

<div class='quotetop'>QUOTE(Etel Rose @ Sep 4 2006, 06:40 PM) [snapback]314279[/snapback]</div>

The front tires should have 2 psi more than the rear tires--the figures are expressed as front/rear pressures.

 

Toyota's "recommended" pressure causes this:

along with low MPG...
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Sep 4 2006, 06:47 PM) [snapback]314288[/snapback]</div>

So Hobbit you must explain to the uniniated what that means? I get it, but I would guess that not everone sees a thousand words.

 

<div class='quotetop'>QUOTE(hdrygas @ Sep 4 2006, 09:59 PM) [snapback]314293[/snapback]</div>

It means that under-inflated tires wear on the outer edges.

Over-inflated tires wear on the Center.

At Toyota's door-panel Tire Pressures (35 Front, 33 Rear), the OEM tires are decidedly under-inflated by this measure. I can see it every day in parking lots.

I've run mine between 40 and 44 in the front depending on mood (and of course 2lb less in the rear), and I got remarkably even wear. I just replaced the OEMs at 40K miles with 2-3mm left before the wear bars, so I could have technically gotten the expected 50K out of them, but I know that tire performance drops off siginificantly before they reach the 'absolutely must replace' point which is what the wear bars really are.