tire pressure - what are your psi's?

I use 42F, 40R, up from dealership 32F, 32R. My average milage improved 3-4MPG.

Makes me happy and the ride is not too bad.

Dennis

 

42 front 40 back (the sidewalls say 44 but I left room for me to make an error)

 

I had mine at 42/40 but have recently lowered to 40/38 to see if it made any difference in road noise. Can't seem to see any difference in mpg but still trying to decide if it makes any difference in road noise.

 

40/38 cold.

 

I have the Toyo Proxis A20 tires, 51 psi max. I am presently using 48 psi cold. I don't bother with the 2 lb difference front/rear, by the time I put 100 lbs of stuff or some luggage in the back the extra 2 lbs in the rear is probably needed anyway.

After 25K miles the tires are wearing just fine, maybe just a little more wear on the edges from cornering.

 

I am running 40psi front and back, which is about as firm as I'd like my brand new Toyo 205/50/16 tyres, to be. I feel this is the best all round compromise, for tyre wear, road comfort and MPG.

 

My placard recommended something like 33/32 [I have the 17 inch wheels] but the dealer delivered it with 40 psi all around. Right now I'm running it at 46/45 psi [sidewall specifies a max of 51 psi for my tires] and I like the handling a lot better.

 

I use the recommended pressures.

 

Goodyear Fuel Max with 51 psi sidewall max. Running 56/55.

PA P

 

37/36 on my stock Yokohama Avid's. MPG's are great and the ride is better. Back in March this year I took a trip to Big Bend, TX. I stayed in Fort Stockton and drove into the park each day. The roads in the park are not smooth. They are asphalt but it has a mild cobblestone look and feel to it. Outside the park the asphalt roads are fine. Also the speeds limit inside the park is 45 mph.

I ran 41/40 psi on the way down to Midland and got 43.5 mpg and then from Midland to Fort Stockton, Big Bend and back to Fort Stockton and got 50.9 mpg. I expected better form the slower speeds and hot weather but the roads were very uncomfortable at 41/40 psi. The next day I lowered my pressure to 37/36 psi and drove from Fort Stockton, TX to Big Bend, TX and back to Fort Stockton, TX and I got 55.9 mpg. then on the return trip from Fort Stockton, TX to a fill up in Chickasha, OK I got 53.4 mpg. This included 80 mph on a section of I-80. (See my Fuelly page march 28 -30th)

I concluded that if you have rough roads that the very high psi has a detrimental effect on my mpg. Obviously psi higher that the stock setting is better but after trying it, I've stayed away from very high psi and done very well 37/36 psi. I have a lot of rough roads in my area. I'm quite sure that if you have smooth roads you can benefit form the high psi that many use due to the decreased rolling resistance. It did not work out that way in my area.

 

Why would this be true? Do you think you have enough data to support this conclusion?

If you are correct it would be very interesting to try to find out why. I can't say I have ever noticed any difference in mileage due to different road surfaces on paved roads although there may well be some. But why would softer tires improve mileage. I don't doubt what you saw but maybe the difference was due to some other factor?

 

Dealer 32F 32R
Now 38F 38R

 

I'm running 40F, 38R. I was at 42/40, but wanted to see the difference. Too early to tell MPG differences, but I think the ride comfort is a little better and I understand the dry traction may improve as well.

I have new Michelin MXV4 at 195/65R15 on the 07 Prius and stock Goodyear FuelMax on the 2010.

 

When we took delivery a year ago the psi was 40f 38r. We have 17" Toyo's. I have maintained them at the original dealer set psi. Our one year average mpg on car computer is 54.8mpg. The actual is a little over 52mpg. We are satisfied with the ride and handling at this psi.

 

The data was in my first post in this thread plus increasing my psi did not increase my mileage here at home over several tank fulls plus >40 psi rides very rough since the suspension has to do all the work.

Back to the Big bend trip data. I did the exact same drive twice with identical speeds and wind/weather conditions with the only difference being tire pressure. 41/40 psi = 50.9 mpg and 37/36 psi = 55.9 mpg on that test.

Because the higher pressure over several tanks at home and with the results of the Big Bend test on its very rough roads, i concluded that the lower 37/36 psi was better for the roads that I was driving on.

I've been road racing bicycles since my teens and am very familiar with high psi tires (120 - 150 psi) and their low rolling resistance benefits. My favorite all time bike is still my 1978 Motobecane Super Mirage with 13/19 Rigida rims and full Campy components.

I was very surprised when the very high pressure did not add anything to my mpgs. Now 37/36 does add over the dealer delivered PSI but not the real high psi. Not in my testing on the roads I have to work with.

If anything, I'd think everyone should test different psi in the own driving environment over several tanks to see what works best for them.

PS, it is 366 miles round trip from Fort Stockton to the end of Big Bend. That's the two trips I compared.

 

Thanks for the information Mark, I think I'll take you advice and do some more tests later this year.

 

40F/38R

47 mpg lifetime from 07/08/09

 

The hardcore at another site go high enough to not put into print for liability and flame war reasons. My seat isn't tough enough for that harsh ride.

I don't go over the minimum required pressure for the tire's maximum load rating. Other people label this as the sidewall maximum.

 

I just had my 5000 miles service today. I had the dealer (after my tire rotation) increase my pressure to 40/40. I hope to see my MPG go up from 43 to 47+.

Planning on doing my Northern to Southern Cal trip next week....we'll see how it goes