in my first installment i said i would go to metrpolis il from nashville and compare the gas mileage done with 42/40 lbs verus the factory settings. yesterday with tires cold i put the air in as listed on the door ie 35/33 exactly. in the past i got between 44 and 47 mpg. well i just go back here are the results. on the waydown at 70 mph and 68mph i got 48mpg. on the way back igot 51mpg!! what the hey!!!!. i know why one trip i ony got 44mpg and that was because it was around 38 degrees and raining like hell with lightning and strong winds!but now i can only guess that its because although when i started this morning it was 37 degrees it warmed up to 65. even so im thinking that the mileage difference between high inflation and "normal" may not be as much as i thought.i did notice that the car was quieter and bumps were much better. the only down side seems to be that of cornering in which "smiley" seems mushier ( not that it was stellar in the first place your intrpid reporter: fred from nashville 8)
Fred, I've found that my mileage takes a major hit when it's raining and there's a lot of water on the road. But I really don't know as much about rain as you do. The only time I ever had to pull over due to no visibility was when I was driving in the south.
that reminds me, dave, about the greatest rain invention i can tout. that is rainx. i use it every once in a while when i know its going to rain. im not advocating this next thing but for me its great. the faster you go the better it works. in fact when im doing about 65 or so in a thunderstorm i hardly need to use my wipers even when im being passed by a huge semi. i really recommend it.!
i always appreciate everyones input. dan, you are becomming my new technical guhru. and of course doc fusco and john 1701a etc. you will notice that my posts are not normally extremely technical but they do try to use my subjective knowlege. but guys like you rock(!) on the tech side. thanx fred from nashville
Fred: My Prius came with Integrity tires like yours. After finding this forum I also played around with the inflation pressure but soon went back to the factory recommended inflation. The roads in and around Winnipeg are in extremely poor condition, with a lot of frost heaves and potholes. If I set the tires to 44F 42R the ride became bone jarring - like a buckboard. In city driving with speeds under 70 km/h I didn't notice any difference in fuel economy. On the Trans Canada most of the time there was no difference, a couple of times I gained almost 3 MPG. IMHO the bone jarring ride was *not* worth the "gain." When I put on the Michelin Harmony tires I also played with inflation and quickly returned to 35F 33R. There was no difference between the Integrity and the Harmony, except at the recommended inflation the Harmony seemed to give a somewhat softer ride over frost heaves. With my Dunlop Graspic DS-2 studless winter tires, I played with inflation pressure quite a bit too. At the factory recommended inflation they ride nicely. At 44 F and 42 R, they still ride ok but the traction on ice was non-existent, just like an "all-season" tire. Actually, I left the Dunlop winter tires at 30/30 most of this winter for city driving. I have found that somewhat underinflated at cold temps actually improved the ice traction. I swapped them last week to the Harmony tires and they're hardly worn at all.. There is potential for increased fuel economy if you could find special low rolling resistance tires capable of 80 psi inflation. I wouldn't want to ride on them though.
i was wondering if the ride over bumps would be significantly better at lower pressures. i have to agree that the ride is better with the softer inflation. i am going to compromise by going to 38/36. then ill feel better 8)
