Tire Pressure

I run mine 3 psi above the posted pressures on the driver's door jam.

 

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<div class='quotetop'>QUOTE(catgic @ Sep 15 2007, 12:40 PM) [snapback]513029[/snapback]</div>

I purchased my very own electric air pump, so that I don't have to waste gas driving to some gas station.

 

<div class='quotetop'>QUOTE(Goddy @ Sep 15 2007, 09:15 AM) [snapback]513018[/snapback]</div>

I don't know if adding wider tires in isolation (e.g. not going to lighter wheels) will improve mileage. You are looking at the combined picture. Typically wider tires on stock wheels will result in an increase in rotational mass, which will in turn reduce your mileage (since the HSD has to do more work vs. the OEM tires). Conversely, if you were to reduce the rotational mass, then you should see an improvement in the mileage. For a point of reference, one PC member (my apologies, but memory escapes as to who it was) noted a 3-4 mpg hit by adding Michelin Pilot Exalto A/S tires in 205/60-15 to the stock wheels. I went the other route and swapped out the OEM wheels and tires on my 2007 Touring edition for 10 lb. forged wheels and Michelin Pilot Exalto A/S tires in 205/60-15 and noticed ~1 mpg improvement (which I would attribute to the lighter forged wheels).

I have since increased the tire pressure to 36 psi all around (from 34 psi) and have noticed another ~1 mpg improvement. I am wondering if I were to go to 38 psi, whether I would have problems with ride harshness (I have back problems, so for me, ride harshness is something to be avoided).

There is a causality to everything....

 

<div class='quotetop'>QUOTE(firepa63 @ Sep 15 2007, 12:28 PM) [snapback]513025[/snapback]</div>

Isn't it true the more air you put in over the door posted recommendation, will also cause the tires to wear unevenly?

 

<div class='quotetop'>QUOTE(Jeffk01 @ Sep 15 2007, 04:35 PM) [snapback]513108[/snapback]</div>

Not even a little. The original reason that Prius drivers started inflating to higher pressures (42/40 is popular) is because the tires tend to wear very poorly at the recommended pressure. The edges round off due to excessive flex and the tires can be junk as early as 15-20k miles. Using higher pressures solves this problem for the most part. Modern steel belted radials maintain a nice flat tread so you won't see excessive center wear. Mine hardly show any wear after 12k mi of higher pressures since the day the car was delivered.

 

I had my 10,000 mile service at my Toyota dealer yesterday, and asked them to set the pressure at 42/40. I knew my tires were currently below that pressure, but hadn't bothered to adjust them on this tank of gas. The dealer actually DID set them at 42/40 this time. I've driven about 30 miles since then, typical driving for me (3 short trips of under 10 miles each and one of 12 miles), and the MFD MPG has gone up from 46.2 to 47.4, as my miles on this tank have gone up to 416 and my gas pips have fallen from 3 to 2. I think that's a pretty dramatic evidence that the higher tire pressure of 42/40 makes a HUGE difference.

 

<div class='quotetop'>QUOTE(Jeannie @ Sep 15 2007, 05:01 PM) [snapback]513122[/snapback]</div>

I pressed the pressure to 50psi the night in May we traded for a used 05. We have ran it all summer including a loaded down trip to Hybridfest and Mall of America.

 

Using anything lower than 35/33 psi Toyota spec. will almost certainly lead to excessive edge wear on the tires. Whether their number (diligently maintained) would do the same, remains to be demonstrated.

Using the maximum indicated sidewall pressure in your front tires, and a few psi less in the rears, will almost certainly slow down tread wear and increase mpg. The ride feel over bumpy roads will be worse. But I am still (still, still) waiting for the first post that demonstrates max sidewall inflation with radial tires causes excess center tread wear under Prius.

Please, all, choose your own numbers within that range. Long history of Prius posts suggests that most of the fuel economy gain will be found in the lower part. Tire longevity increase will probably be linear throughout the range.

Still hoping that someday we will test wet and dry road traction vs psi, with Prius, on some test course. My expectation is that the higher inflation pressures would do better. If someday that test gets done, surely it will be chronicled here.

 

I use 42/40 and saw a jump in mpg. Been thinking about going to 44/42.

 

<div class='quotetop'>QUOTE(Neicy @ Sep 16 2007, 08:22 AM) [snapback]513266[/snapback]</div>

I run the stock Integrities at 45psi but don't mind the stiffer ride. Increase the tp a little bit at a time as long as the ride is still comfortable.

 

I run 44psi front and 42 rear in the standard 195-60H 15 Michelin Energy tyres. Ride is fine 4.3L/100km but a little noisy at speed on some surfaces.

 

I've been running 42/40 for the past 6 months or so, and am right at 51.5, with 99% freeway driving between 65-80 mph. I have 0ver 42,000 on the original Goodyears, and the tread only looks 1/2 worn. I know there is lots of whining about the OEM tires, but I can't see changing them until they are gone, and mine don't seem to be going away anytime soon. High pressures are better for the tires, than too low (factory recommended).

 

42-40 since the day after purchase summer of 2006. stock tires have worn very evenly, but are now worn out. now i need to shop for new tires before winter sets in..........

 

I have an 07 that I bought in May and just started reading on PC since 18 Sept and Have noticed people talking a lot abought getting a certain amount of miles per tank and MPG. I have read enough about the tire pressures that today I went out and checked what my dealer had them set at and to my surprise I had 28psi in all four wheels! I have been averaging around 45 with this set up and I have also been getting around 525 miles per tank and have never seen the last pip on my fuel guage blink? Usually I put around between 10 and 11 gallons in when I fill up. Be advised that if you leave the fuel nozzle in after the first click off of the fuel pupm you are risking the fuel tank puking all over you. Best way to get a "real" fill up is to remove the nozzle after it clicks off and then while holding the nozzle loosley in the tank opening slowly fill the tank till you see the fuel at the top of the filler.I have also got a high of 55.9 mpg on a trip we made in June shortly after buying the car. I just put 38/36 in my tires and can't wait to see if that makes any difference in mileage.

 

44/42 here. I just rotated mine at 10K miles and didn't notice much wear to speak of. If anything it appears the edges are getting worn more than the center of the tread, which is normal I believe. I imagine the edge wear would be quite a bit worse at lower psi. I haven't noticed any problems with it riding too stiff or anything like that and never had any passengers complain (even my wife who certainly would let me know if it was a problem).

 

is it best to inflate tires after they are hot from driving, so you know that when you put 44 psi they will not increase in psi?

 

<div class='quotetop'>QUOTE(pingman @ Sep 25 2007, 04:52 AM) [snapback]517339[/snapback]</div>

I believe you should fill them up after they are cool all the way up to the max sidewall pressure or whatever psi you choose. So in the mornings after the tires have cooled down should be the best time to inflate them to the desired psi.

 

<div class='quotetop'>QUOTE(treehggr @ Sep 25 2007, 08:47 AM) [snapback]517349[/snapback]</div>

I concur. The max psi listed on the sidewall is for a cold fill and includes a factor of safety for expansion under operating conditions.