Hey Guys,

I just installed Kumho 275/70HR16 ECSTA STX tires (51 PSI max per spec.) on my 2001 Supercrew 4x4 and was wondering what's the best air pressure to use for every day driving. The driver's side door says 30 PSI front and 35 PSI rear; the tires look way under pressure, even feels sloppy going around corners. Maybe that was for the original Goodyear Wanglers 255/70-16's. The garage that installed the tires put 40 PSI in and on the way home it felt much better. I want the safest performance out of these tires.

Thanks for your comments in advance!

 

The pressure on the door jam is for the truck for all tires. If the max pressure for the tire is higher than the truck then it probably is has more capacity than is needed for the truck.

That is probably the case with this tire. Since the pressure difference is as much as it it you can add a few pounds of pressure if you like the stiffer ride, but it is not necessary and may give you more tire bounce with will impact handling.

I don't think it is necessary to put more pressure in than half the distance between the two numbers. For example, half way between 30 and 51 is 40.5.

Also, keep in mind that the max pressure is an off the truck cold pressure. Driving down the road, heat will add pressure to the tire. You may have to add 2 lbs to adjust for that.

If it were me, and it's a daily driver with no load I would try 35 front and rear and see how it rides and handles.

 

Thanks for the info greencew. The main reason for asking is safety; the sloppy feel bothered me, but if it's the right pressure on the truck then so be it. These are H rated tires too and I want to make sure at higher speeds heat would not build up and become an issue. I also heard that the higher pressure provides better fuel mileage in some cases - what do you think?

 

I agree. There is a direct relationship between tire pressure and fuel milage. Thing is, the bounce bounce bounce has to be worth the fuel milage.

The stiff 4X4 ride of a truck is due to the tires more than the design of the truck.

I had the Goodyear Wrangler ATS tires with a higher load capacity on my 99 4x4. They took 44 psi max. I ran them at 44 for the first year because that what what the tire said. It was a rough ride and the back end skipped down the road.

This past spring I had two F-150s, a 4x2 and a 4x4. I swapped tires between them and the ride characteristics followed the tires.

I now run tires designed for a 4x2 on my 4x4 and enjoy the ride.

 

You have to keep in mind that you must keep the same weight carring capaity as OE

OE tire 255/70R 16
Front tire air pressure 30psi=2106 lbs x 2=4212
Rear tire air pressure 35psi=2271 lbs x 2=4542
OE Load 8754lbs this is the magic number Ford wants the tire to carry this much lbs this number is based on the truck full of gas and as many passengers the vehicle is designed to hold

New Tire 275/70R16
Front tire air pressure 26 psi =2238 lbs x 2 = 4476 lbs
Rear tire air pressure 29 psi =2359 lbs x 2 = 4718 lbs

NEW LOAD 9194 lbs I added a little more for unexpected extra loads 40 psi is too high after a while u will develop Heel and Toe wear and the tires will become noisy

Also keep in mind you have gone from a light truck tire to a high perfomance light truck tire (P-metric to a euro metric which has no designation in front of the numbers which means it has a higher load carring capacity than the OE P-Metric tires)

Just my professional .02 cents