This is, of course, the right answer. ^^^^

However, both the vehicle mfg. and most safe drivers, prefer a little oversteer, which is why there is always a preference for a little more tread on the ground on the front tires. Hence the lower numbers up front (see below). I think that about 10% lower in the front than the formula you stated is about right. Still, for a completely empty E250 4WD that formula will still result in a higher pressure in the front despite what the mfg. says on the door sticker. Its been a while since I have had a van at a truck scale and the mfg. are understandably reluctant to publish front and rear empty van axle load numbers since the numbers are so bad, but I'd be shocked if an empty cargo E Series does not start out at 55/45 or worse.

I am quite sure that mfg. safety concerns and law suit worries results in the door sticker pressures to be based on a fully loaded van if not specified. Otherwise, a person with 12 passengers and a full load of fuel would be flattening the tires.


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Lower pressure = more tread area on the ground. Because, tread area = load divided by tire pressure. A front load of 4000 lb. and 40 psi equals 100 square inches of tread on the ground. At 50 psi it drops to 80 square inches and therefore less road traction in cornering. Hence potential for understeer (not good) if the rear has even more rubber on the ground.

 

Understeer is 'safe'. Most modern vehicles (I would argue almost all, especially with traction control) will default to understeer, or actively attempt to encourage it via traction and stability control if you exceed the limits.

With understeer you don't have to hold any oppositelock, and your vehicle isn't trying to get backwards. With understeer, its much harder to flip your vehicle, which is a big killer in our vans.

Lawyers see it like this: If someone understeers off a corner, they were just going too fast. If someone flips over a 3 inch curb, then it's could be a dangerous vehicle.

 

Again, an interesting discussion. I like this van forum.

To me, oversteer is easily correctable without stabbing the brake pedal which is always a chancy response and the only way to get back on the right side of the road when understeer has come into play. But, I can accept that others may be willing to widen a turn instead. But, I think one is hard pressed to find many public proponents of understeer, in the end it is a personal choice.

 

My personal car collection reads like an Axis of Oversteer, with a CTS-V, a Chrysler 300 SRT8, a Ford GT, and recently a turbocharged Saturn Sky Redline. Cars I have formerly owned include an Audi RS4, and a Porsche 911. I like oversteer. Its a Good Thing(TM) in my mind. My SRT8 eats rear tires on the track like they are candy, and is by far the most ***-happy of my current stable. I actually keep spare sets for it and the Saturn in my race trailer.

Most drivers, when faced with a car that is responding strange, will stab the brakes or release the gas. If you are in an oversteer situation, both are a good way to be facing the other direction in very short order. The correct response is to turn into the slide, guide the nose of your car into the corner, and tame the slide with throttle control. This actually requires experience, skill, and not being a total idiot. Understeer is a bit different.

Understeer is caused by a lack of front tire traction. When you apply braking power, you transfer weight to the front tires, increasing traction. In an understeer situation, braking can correct your vehicle without putting you into a spin. And, traction control systems work with the brake and torque management to shift the weight of your car, and recover from understeer rather easily. Idiots can handle understeer, and new cars are built for driving idiots. To isolate them from the task at hand (driving.)

This is why tire shops insist you put your new tires on the back. If your new tires are on the front, they have more grip and your car will oversteer much easier.

 

The explanation above ^^^ is counter-intuitive to everything I know about driving. Amazingly, however, it is completely correct. For the rank and file, inattentive driver (90% of all drivers I suspect), understeer is the safest characteristic as between understeer and oversteer.

And, as many times as I have put new tires on the front, the experts says, as the poster above did - put them on the rear.

Now, admitting that I am not in the mainstream of thought on this does not mean I am going to change anything. Coming from a background of Porsches and various over powered cars, I love oversteer and will do anything to avoid understeer.

That said, this post above ^^^ is very informative.