The driver side door lists manufacturer recommendation for PSI. 30psi front and 35 psi in the rear(1998 Expy 4.6). Can someone explain why the front should be less than the rear? I've always kept my tires (all 4) at 35psi. What PSI will give the best gas mileage?

John B.
1998 Expy 4.6

 

I dont have an exact answer, but at least with the factory tires mine handled better at thier reccomendations. If i even added 5 lbs to the front it would be all over the road. Its one of those things you have to just do some experimenting.
The greater the pressure, to a reasonable extent, the better the fuel milege. This is due to the fact that with more air in the tires, the footprint that contacts the road becomes smaller. This in turn gives you a lower rolling resistance. This also gives you less control, for the same reason. And will reduce the life of your tires by wearing out the centeres. Its something you just have to experiment with.
I drive a 98 4x4 with the 17" wheels and tires. I run 32 in the front and 35-40 in the back, depending on whether im loaded or not.

Tony Warren
Nebraska

 

I forgot to mention that I have 16 inch rims and tires....

John B.
1998 Expy

 

That wont make much difference. If you want to experiment, try putting 35psi in the front tires and see how it handles on the open road. You should be able to tell an absolute difference in handling. Mine will be all over the place. Then air them down a few psi and drive again. Keep doing this until you find where yours handles the best, just dont go under 30psi.
The rear pressure wont effect handling much, more ride quality. I wouldnt go over 40 unless youre loaded, or youll wear out your tires.

Tony Warren
Nebraska

 

There are lots of reasons for having different front and rear tire pressures. First of all the maximum loads on the front and rear axles are not the same. The maximum front axle loading is 3500 lb (for a 2000 4x4). The maximum rear axle loading is 4128 lb (for either a 4x4 or 4x2). This alone should imply that the tires have different inflation pressures. Pressures are also adjusted differently front to rear to change the handling characteristics. My 1997 Expedition was delivered with all tires inflated to 40 psi. It was almost undriveable. After adjusting the pressures to the Ford recommendation, it drove fine. Increasing the pressures in the front tires makes the front very nervous - it was too responsive to my tastes. Decreasing the pressures to the recommended level got rid of the twitchiness and most likely increased the grip of the front tires. You might enjoy reading the information at:

http://www.tiresafety.com/service/serv_nav1b.htm#recip

Here is a little of what this site (started by Firestone) has to say:

"Recommended Inflation Pressure

"Many people ask "what air pressures do you (meaning tire companies) recommend for cars under normal conditions?" The answer is "we recommend what the vehicle manufacturer recommends." Many people mistakenly believe the only reason vehicle manufacturers recommend certain air pressures is for ride comfort.

"What criteria do the car manufacturers use to determine inflation recommendations?
- Ride
- Load capacity
- Traction, wear
- Fuel economy/Rolling resistance

.....are all correct. But, consider another question:

"Why did Ford recommend 30 in the front and 34 in the rear on a 1997 Crown Victoria?"

"The additional air stiffens the sidewall and makes it more stable. In order to achieve the handling, tracking, and other driving characteristics, one of the things the manufacturer can do is balance front to rear handling by adjusting the tire pressures. In adding the same air pressure in the front as the rear you will change the handling characteristics from what the manufacturer intended. Quite a few station wagons and light trucks have different pressures for the front and rear. But, it's not just station wagons and light trucks; it's also Porsches, Nissans, Corvettes, Hondas, and BMW's to name just a few."

Regards,

Ed White

 

Thanks for the responses, I'll have to play around with lower psi up front....I also wonder if it will affect gas mileage....

John B.
1998 Expy 4.6

 

The lower psi will very slightly decrease your milege depending on your driving conditions. Youll save more by ensuring your pressure doesnt decrease the life of your tires by being over inflated. Theres kind of a happy medium you have to find.

Tony Warren
Nebraska

 

 

Hi,
When my '97 XLT, which manual said 30 front, 35 rear(4x4, 5.4, 17" wheels, Goodyear RTS (yuck!)with air suspension)was new I played around with tire pressures and found that increasing the front to 33 lbs and having the rear at 36 accomplished these things: best handling on smooth or rough pavement, with or without a 5000 lb trailer behind; 60K miles from one set of tires, 1 mpg better gas mileage, no increase in driver fatigue on long trips. The same has held true for the second set of tires Michelin LTX M/S (hooray!) over the last 55K miles, and I've got another 10K left on the Michelins. I keep the 3lb differential regardless of load and it works for me.
Hope this helps.

 

My truck for whatever reason does not have the tire pressures marked at all.

I own a 97 Expedition Eddie Bauer with 5.4 4x4. I have the 17" Wrangler AT's on there.

What PSI should these be set to, same as above 30 front 35 rear ?

Thanks

WC

 

I've noticed that my Expy handles real squirrely with 35/35. I have also noticed that I can tell when one of the tires is a little bit off - it handles like crap. I've found that it really does drive the best with 30/35. I think the 35 in the rear may be for towing purposes.

XXL

 

Thanks for the advice. I noticed you have the Hellwig sway bar snd the shift kit, how do these perform ?

Thanks

WC

 

Wildcat,

I checked for my sticker just this weekend after seeing this post last week. I found the sticker on the driver's side door along the side. I actually missed it the first time cause I was looking on the inside jam rather than the door.


Mine also said 30 front and 35 rear. Seems like a general pressure for all Expeditions.