Tire Pressure

A contributor on another forum is advocating running the 18-in.
Bridgestone tires on the 07 Santa Fe at 38-40 psi., rather than the 30
psi recommended by Hyundai. He suggests this gives a better and safer
ride. The max. on the sidewall is 44 lbs. Do any of our experts have any
thoughts on this?

 

It all depends on what you're looking for. The Santa Fe is heavy enough
that 30 is probably not enough for even tire wear. But I'd surmise that
38-40 will wear out the centers. My suggestion would be about 35 PSI for
optimal tire wear.

 

Can't really speak to the Sante Fe, but on my 2007 Entourage, the door
sticker says 32 PSI. The sidewall, like yours, says 44 PSI MAX COLD. I
have tried everything between the two numbers and 38 PSI seems to be the
winner for me. Above that and I get a bit of a harsh ride. Below that and
the turn-in isn't quite as crisp. I also seem to get a hair better gas
mileage at 38 PSI, but I don't really have enough data yet to support that
as a conclusion.

Eric

 

I ran my old Isuzu Rodeo with more tire pressure in the range you're
talking. I got fairly even tire wear but damn if I didn't burn out the rear
wheel bearings. Related ?, well maybe from the extra uncushioned pounding
over the years?
Another consideration anyway.
BCinBC

 

I have noticed that Hyundai likes that 30 psi number - don't know why. It
is also the recommended pressure for the Elantra.

With my Elantra, I thought that, at 30, the tires rode too soft and wallowy.
My "ultimate" pressure seems to be between 34 and 35.

I would agree that somewhere between 34 and 36 would be optimum. Also agree
with HyundaiTech that I might try 35 first, and check your ride, etc.
Conceivably, you could try 100 miles or so at 34, another 100 at 38 and so
forth, just to see how they ride. But in terms of wear, you would need many
more miles than that.

I must caution you regarding even slight "over-inflation" of tires. While
it is a small risk, higher center of gravity vehicles (like SUV's like the
Santa Fe) are more prone to rollovers at higher air pressures. Ford, in
taking that problem to the extreme with their troublesome Explorer, actually
recommended 26 psi specifically to reduce the rollover rate. They also
specified a Firestone Wilderness tire that, at the time, only had a
government temperature rating of 'C' (current Wilderness's have the more
common 'B'). The results were disastrous and well known.

Again, a very small risk but something to keep in mind.

Tom Wenndt

 

Tom,

What is the source of your information here? This is exactly opposite
my understanding. The extra distortion of tires at low pressure more
than offsets the slight additional CG height in an abrupt maneuver.

http://mb-soft.com/public/rollover.html


Matt

 

In theory, what you say is true, and I don't dispute that - and as your
source points out, in most cases, that is the case.

But it would take me way too long to get you to the best source for the
Firestone Wilderness/Ford Explorer debacle. There is a ton of information
out there from that.

But Ford had to readily admit that the rollover worry (which was really more
of a design flaw in the Explorer more than anything else) was the reason
they specified 26 psi.

After the spotlight got turned on the matter, Ford changed their specs on
the Explorer to 30, which in my book is still a tad low for a heavy SUV.
But they clearly were worried about rollovers.

Of course, the less air in the tire, the more there will be a problem. My
suspicion is that the reason the Firestone/Explorer thing was SO bad was
that, in most cases, the tires that were blowing out probably didn't have
anywhere near 26 psi in them. Until this happened, way too many people
didn't check their air pressures regularly. With slow leakage and such, I
am betting that many of these tires didn't have over 20 psi in them. At and
around that pressure, your source here is right on the money.

Thanx for writing.

 

If memory serves, it was pretty well publicized in the Ford Explorer issue
that Ford's empirical data showed that 26PSI made the vehicle less prone
to roll over, and that's why they recommended that pressure.

If memory serves further, the reason for the rollovers was because of the
tread separation of the tires, causing a significant loss of pressure or a
blowout, leading to loss of control of the vehicle. As I recall, there was
significant evidence that the reason for tread separation was due to the
overheating of the tires, which can be at least partially traced back to
the horrendously low 26 PSI recommendation.

 

OK, you made a claim with no data to support it. I understand.

Matt

 

I searched around and found no such claim by Ford. I saw claims that
the lower pressure allowed the tires to hold the road better and reduced
some vibrations in the tire/suspension combination, but I saw no claim
from Ford about lower tire pressure reducing the roll-over potential,
and I believe that physics suggests this simply isn't the case.

Matt

 

A contributor on another forum is advocating running the 18-in.

I run my Yokohama H4s on my 02 Sonata at around 32-34 cold and they
perform the best. They're rated to 40psi max so I am well under spec
and have experienced fairly even wear. You ought to stick around 34-37
depending on your driving habits because even though your tires might
be rated up to a max of 44psi, you do experience uneven wear as you
move up to the max spec numbers. You'll have to find a psi sweet spot.
The next time you go for tire rotations, ask the techs to give you
depth reading from the sidewalls to the center and this will give you
an indication if your wear is even or not. Of course, it also depends
on the tires too. Some have slightly softer centers, some not. They're
all made different. good luck.

- Thee Chicago Wolf

 

A lot of work goes into qualifying a tire for a vehicle manufacturer.
The placard pressure is given as the best optimum pressure for a wide
variety of tire characteristics.

Higher pressure will generally NOT give a smoother ride - in fact the
opposite is true. Higher pressure will decrease the amount of contact
area between the tire and the road which will reduce traction on sry
surfaces. Going from 30 to 40 PSI is a huge jump and will likely
increase irregular wear and possibly noise.

The pressure on the sidewall should be ignored. That number comes
from a tire standardizing body and is unrelated to the specific
vehicle/application.