I bought my 2007 in March and the dealer delivered it with 40psi all around so I kept it there to help the mpg. Since new, I have been mildly annoyed by the sensitivity in crosswinds (especially going down I-5 when the afternoon winds are gusting) as well as the harsh ride. I even pulled off the interstate and dropped the tire press in the rear by 3 psi one afternoon, to try and reduce the blowing around (it helped).

So I took it in for the first service this week and asked the dealer to check the alignment at the same time, which they did (spot on). They also rotated the tires, and when I got the car back I immediately noticed a more compliant ride, less wandering, and less sensitivity to gusts. I guessed they had dropped the tire pressure since it drove so different. By the time I had put 50 miles on the car I didn't care - it was that much nicer to drive.

Well, I checked them when cold this morning and they are at 36 psi all the way around. Only 4 psi less than before. Needless to say, it's staying there. I have never had a car respond so dramatically to tire pressure. Yes, my mileage appears to be down 1-2 mpg, but imho it is well worth it. It just feels so much better to drive - ride, tracking, etc. I will report back with mpg and overall impressions when I have a couple of tanks on it.

Just remember to keep a 2PSI difference (so either 36/34 or 38/36). I have mine at 38/36.

Mods: EV mod, VVT-i emblem, sport pedals, OEM cargo mat, JDM Prius interior footwell lighting, Sylvania Silverstars 9003ST, DICE iPod kit, OEM all-weather mats, TomTom ONE v2, LED licence plate lights.

There are always trade offs and tire pressure is one of them. As an experiment, when you next pull off after a high speed run, touch the tire treads and feel the temperature. The heat you feel is the lost energy BUT the quality of ride is also important. There is a lot to be said for arriving in a happy state of mind.

My commute involves modest speeds, 25-38 miles per hour, on urban streets. I have one short segment up to 55 miles per hour but otherwise, I'm in hybrid heaven. My last interstate trips were at 42/40 psi on the previous set of tires and since then, I've also fixed the rear wheel alignment.

Bob Wilson

Operation Iraqi Oil Freedom:

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My other 1500 cc car:

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I am going to 38/36. The 36/36 gave a very nice ride but mpg dropped by 2 mpg. I am hoping that a bit more in the front will help that slightly and still retain a bit of the ride improvement. I never felt a car so sensitive to air pressure, but it makes it easy to tune.

Tire pressure (Higher) is your friend!

Look Prius rookies. You need at least 42/40 Front/back to have any shot at cracking 52 mpg. As for wind issues. It's called a BT brace. Buy it. Install it. Drive it. You will be a believer and your Prius will handle like a mini cooper

Why?

The usual reason given is to help the anti-lock brakes work properly. However, I would also add that the weight on the front tires is greater than at the rear. A higher tire pressure is how to handle a heavier load.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

because there is quite a bit of weight over the front wheels (just look at the engine position relative to the front axle. It's ahead of the axle by quite a bit.

Besides, even on "regular" cars that don't need a pressure difference, having the fronts 1 or 2PSI higher can help (very slightly) with handling because of the extra air pressure in the tyres (slightly less compression under braking or cornering).


err.. no you don't. Mine's 38/36 and I've broken 60mpg. (over a tank, it was 59mpg). I also think the people here don't appreciate being called rookies.

Mods: EV mod, VVT-i emblem, sport pedals, OEM cargo mat, JDM Prius interior footwell lighting, Sylvania Silverstars 9003ST, DICE iPod kit, OEM all-weather mats, TomTom ONE v2, LED licence plate lights.

I still don't understand. All front engine vehicles have a lot of weight up front and their tire pressures are mostly the same. So what makes the Prius setup any different?

It is this group of Prius owners that is different. From the early adopters to today's Prius advocates, we're the hybrid equivalent of a 'hot rodder' with an interest in getting the maximum performance. But I'll share one empirical data point.

When I had my tires rotated, the fronts had worn down to ~.55 inch while the rear tires had worn to ~.75. The difference could easily be the heavier weight on the front tires. By running them at a higher pressure (and 2 psi may not be enough,) they should suffer less wear.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.