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?

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.



<perfbm> wrote in message
news:1160842203.607730.180060@i42g2000cwa. o...
> 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?
>

<perfbm> wrote in message
news:1160842203.607730.180060@i42g2000cwa. o...
> 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?
>

Put in 42 front, 40 rear for maximum mpg.

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:
> <perfbm> wrote in message
> news:1160842203.607730.180060@i42g2000cwa. o...
> > 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?
> >
>
> Put in 42 front, 40 rear for maximum mpg.

<perfbm> wrote in message
news:1161024292.134048.136190@k70g2000cwa. o...
>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?
>
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.

<perfbm> wrote in message
news:1161024292.134048.136190@k70g2000cwa. o...
>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?
>

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.
--

Ray O


>
> Ron Sleeter wrote:
>> <perfbm> wrote in message
>> news:1160842203.607730.180060@i42g2000cwa. o...
>> > 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?
>> >
>>
>> Put in 42 front, 40 rear for maximum mpg.
>

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
news:74db6$4533db37$44a4a10d$929@msgid.meganewsser vers.com...
>
> <perfbm> wrote in message
> news:1161024292.134048.136190@k70g2000cwa. o...
>>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?
>>
>
> 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.
> --
>
> Ray O
>
>
>>
>> Ron Sleeter wrote:
>>> <perfbm> wrote in message
>>> news:1160842203.607730.180060@i42g2000cwa. o...
>>> > 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?
>>> >
>>>
>>> Put in 42 front, 40 rear for maximum mpg.
>>
>
>

perfbm wrote:

>
> do other cars do this too?
>

My 2005 4WD Access Cab Tacoma does the same.

On 14 Oct 2006 09:10:03 -0700, "perfbm" <perfbm>
wrote:

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

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.

>do other cars do this too?

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 >>--

On Wed, 18 Oct 2006 06:26:37 GMT, Bruce L. Bergman
<blPYTHONbergman@earthlink.invalid> wrote:

>The early VW Beetle and Porsche 911 series have the
>same layout and a similar rear pressure higher stagger.
>
> --<< Bruce >>--

With a slightly different reaction to the throttle.....

--

Scott in Florida