Tire pressure and mpg

See the following threads:

http://priuschat.com/forums/viewtopic.php?t=1179
http://priuschat.com/forums/viewtopic.php?t=1260

For what it's worth, my purely anecdotal experience is noticeably better display mileage at 40/38, with noticeably sharper feeling ride. 35/33 or lower (NTB only filled to 32 when I changed to Michelin HydroEdge) "feels" softer or less harsh. With the HydroEdge, the rolling feel of the tire seems mushy at lower psi, like you're driving through mud.

 

Make sure that you get your alignment checked, that all the tires are set exactly right and visually inspect the tires for any anomalies. I say this because higher pressures typically give you better handling at high speeds (should be less skittish).

There should be no rattles, the higher pressure is just bringing them to your attention so I would check to make sure that the trunk is locked in place then look to see what else is loose and batten it down.

I am a big proponent of high pressures, both for better fuel economy but it actually started as a method to achieve that maximum safety and performance from the tires (better stopping and turning, and a lot better wet weather stopping and turning). The increase in fuel economy was just a very happy side benefit when I experienced it so many years ago.

Also, the stock tires are quite mediocre. If you are a sensitive driver, they are skittish at all tire pressures but less so at higher pressures. The feedback I've been reading from Prius owners is that they are much happier when they change (to hopefully better) tires. Don't forget to select low rolling resistance tires when you do replace your tires so you don't lose on fuel economy.

 

I have a question - why all the concern about exceeding 35 or even 40 psi on our tires? My Prius oem tires indicate a maximum psi of 44. I have always used the maximum psi (usually 35) on every car I owned. In over 30 years of driving I have never had a blowout, and none of my tires ever showed over-inflation wear. In fact, even running at the tire's max psi, I generally show under-inflation wear patterns. Or has something changed with tire maker's psi recommendations lately?

 

think about when you hit a pot hole, the pressure increases. i don't think you want to be running normally at the max rated pressure. you want some leway for situations like that.

-drew

 

Originally coming from New York, I grew up on a steady diet of daily pothole madness We had far better results with higher pressure compared to my friends that ran factory specs (18 to 24 lbs for many of them). I experienced less punctures and deflations (where the pressure was not high enough to keep the tire on the wheel and it would pop the bead) and the slightly increased firmness was not noticeable after a day or two, those big potholes are big regardless of pressure.

If you are worried about the tires, they care designed to withstand far higher pressures that we run them at. Keep in mind that the manufacturer designed the tire to run at max pressure at max speed to get its sidewall (UTQG) ratings.

I doubt there are any of us that run our Prius at 112 MPH all day long, day in and day out., but lets jump to Europe where I have friends that have done exactly that. What do they do in Europe? They keep the inflation pressure on the high side and especially those that have access to high speed roads. They all cite the same thing. Improved fuel economy, improved safety, improved control.

Even the one freind that used to run a Ferrari on the autobahn and autostrada almost constantly didn't have any problems with the ride quality and just would not back down on pressure no matter how much his middle aged kidneys got shaken and jostled.

As for potholes, he tells me the potholes in New York are wimpy in comparison to hit he had to hit at high speed. Problems? None. Would he lower his pressure? No way? Where did he get his pressure information from? Directly from the source in France, Michelin. As a multi-millionaire in a high end corporate position, he had all the automotive contacts I wish I had. Fortunately he was happy to share a lot of info with me and I am doing my best to share with you guys the best info I can.

If you think 44Lbs is high, what about trucks that run at 60Lbs, or bicycles that run at 110 Lbs plus? If I ask my competitive friends to drop their tire pressure to a more reasonable 80 Lbs, they would tell me that I'm nuts. They would have to pedal so much harder (poorer rolling resistance) and get sloppier handling. As for potholes, they say that a hard pothole is hard regardless and the small ones aren't worth giving up the high pressures for.

Would I like to have a soft cushy ride, sure, as long as I don't get seasick but do I want to give up on max fuel economy and safety/performance - no way

 

"Also, the stock tires are quite mediocre. If you are a sensitive driver, they are skittish at all tire pressures but less so at higher pressures. The feedback I've been reading from Prius owners is that they are much happier when they change (to hopefully better) tires. Don't forget to select low rolling resistance tires when you do replace your tires so you don't lose on fuel economy.[/QUOTE]"

This is my first post. I appreciate very much all the information in this forum. I have a 2001 Prius. I normally inflate the tires to about 44 psi. I bought two Bridgestone Potenzas recently and put them in the rear. In the front I have two Bridgestone Potenzas with 13,000 miles. I filled all to 44 psi, and I experienced handling problems at high speeds (65 mph). The front end moves sideways as if the wind were pushing it around. I have never experienced this problem in the past.

I went to the tire place and the guy said that the problem is that the inflation was "too high." He lowered it to 32. I said, no, it is supposed to be at 44 for good mileage and better wear, but he disagreed. I put the pressure at about 40 and the problem seems to have gone away. What gives?

On the Bridgestones, the max pressure is 50, but the note on the side of the tire says, "Do not inflate above 40 psi."