why prius front tire pressure higher than rear?

prius tire pressure spec says 35 psi front, 33 psi rear
just wondering what the technical reason for this is?
do other cars do this too?

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My guess is that since the Prius is front wheel drive, the higher pressure will help improve fuel economy. Lower pressure in the rear reduces some of the ride harshness.
It is more common to see higher tire pressure specified for the rear tires, especially for rear wheel drive vehicles, because that is where the cargo is usually carried.
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The front axle of a front-wheel drive car carries 55%-65% of the total car weight, requiring more air pressure in the front tires. Additionally, the front axle is carrying 80%-90% of the total car weight under heavy braking, when the "weight-shift" causes the car to nosedive from the deceleration.
Dick

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Put in 42 front, 40 rear for maximum mpg.
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I did this to try to compensate for the tread wearing more at the edges than at the center. I can't say that I've seen any difference in mpg.
Al 2005 with 20K miles
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     snipped-for-privacy@hotmail.com "Ron Sleeter" writes:

Um. I mis-read the pressure chart on my Prius and over-inflated the tyres. Fortunately, not long afterwards I happened to visit the dealer/garage (the same that gave out champagne to compensate for a recall's "hassle") and happened to mention the pressure I'd used... A strained look crossed the face of the dealer-bod, who suggested that he take the car aside and adjust the pressure down to what was _actually_ recommended on the chart. He did and the mpg stayed much the same: currently getting around 57mpgUK. OTOH I suspect tyre life and the safety of my ride improved. (FWIW, I don't have the tyre pressure tables handy.)
(BTW, 57 mpgUK == 45.6 mpgUS.)
--
Andrew Stephenson


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I read elsewhere about this use of 42 psi for mileage, but it seems to me it would compromise safety by decreasing skid threshold in the event of a rapid stop and/or rapid maneuver on wet roads?
Ron Sleeter wrote:

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Maybe by one percent. Proper inflation is important to minimize the possibility of bruise breaks from hitting pot holes and stress fractures leading to a thrown tread. The 42/40 pressures recommended by many (I use these pressures) are within my tire's rating.
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I have never heard of the term "skid threshold" but if you are talking about the point at which the tires lose traction with the road surface or something like the coefficient of friction, then the higher tire pressure doesn't compromise safety. There are so many variables that affect tire performance and tire life that a change in 1 variable will be offset by changes in others.
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My wife and I have noticed that the difference between the 35 lbs that my dealer uses and the 41 I put in at the next fill-up is about the difference between 42.x and 47.x Avg.MPG. We have never had any problem with traction. Here in Tidewater VA we run about 60/40 interstate/street. I-64 is concrete mostly with longitudinal drain groove cutting. (don't know if that makes any difference or not, but it makes some nifty 'whistling' at 60 when the pavement is new and the grooves are just put down.)
Carl Powell
"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message

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snipped-for-privacy@yahoo.com wrote:

My 2005 4WD Access Cab Tacoma does the same.
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It's to keep your high-beams high enough off the ground. mark_
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wrote:

Because more weight is in the front of the car than the rear, so with a light load you want the pressure a bit higher at the heavy end to keep the tire wear even.
I'll bet it calls for 35 and 35 if you have four or five passengers and a full load in the trunk for a trip - and if not, that's where I'd put it. If the sidewalls allow higher, I'd bump them both up to the maximum pressure if you are carrying a maximum load.

Lots of cars do, some far more pronounced than that two-pound split. Whenever all the weight is at one end, the tire pressures have to be staggered to match.
My Chevrolet Corvair (rear engine aft of RWD axle) has a severe rear weight bias and calls for 14 PSI front, 28 PSI rear. (With radials, I ran it at 18/32.) The early VW Beetle and Porsche 911 series have the same layout and a similar rear pressure higher stagger.
--<< Bruce >>--
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snipped-for-privacy@yahoo.com wrote:

something to do with weight distribution.
I tried running my Classic Prius with the same pressures front and rear. I didn't do that for long - the car felt like it would fishtail at a panic stop, whereas with a +2 or +3 psi difference in the front it would stick those same panic stops. (Beware of those Dunkin Donut shops in the morning commute!)

My cousin's Chevy Malibu is 29 psi front, 26 psi rear.
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snipped-for-privacy@yahoo.com wrote:

Fairly normal, certainly every car ive owned/driven has had higher front pressures than rear. Its due to the weight distribution of the car - the heavier front end requires more air to maintain the same contact patch and sidewall deflection.
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