E series tires

[flyfisher]

Well, I have to report that my new (about 2,000 miles) 285/75/16 "E" rated BFG AT's are pretty scary on wet roads, and in the Pacific N-West, we own the book on Wet Roads. Coming across Snoqualmie Pass today, riding into the teeth of the first Pineapple Express of the season was pretty spooky. I don't remember The Van being so loosey goosey with the "D" rated tires. I have them aired up to the recommended 80 in the back and 60 in the front, sort of like ice racing on Lake Erie.

I'll be driving slow and in the right lane between October and May...

Tom

[j.whitbread]

Flyfisher, you might have too much air for the wet roads. 80 psi is MAX.

[flyfisher]

j. whitbread, I'm going to reduce the pressure, just to get a little more contact with the road. A 9,200 lb Van on a "plane" wouldn't be a pretty sight.

Tom

[j.whitbread]

I have mine between 50-55.

[Ford_6L_E350]

A diesel van weighs more, so I have mine at 65psi front and rear. We could give you better guidance if you fill in your signature so we know what van, engine, options you have.

Mike

[flyfisher]

Originally Posted by Ford_6L_E350

A diesel van weighs more, so I have mine at 65psi front and rear. We could give you better guidance if you fill in your signature so we know what van, engine, options you have.

Mike

Thanks Mike, I have a 2005 SMB RB50 with the 6.0 PSD (lot's of initials here)

[Ford_6L_E350]

Based on the weights of other similar SMBs, you probably should be running 65 psi front and 55-60 psi rear. You really need to weigh the van (fully loaded) to get a more accurate idea.

Mike

[flyfisher]

Mike, The Van weighs 9,220 lbs, with me, and full water, fuel and propane tanks.

Tom

[Ford_6L_E350]

The best method to calculate tire pressure requires weight measurements for the front and rear of the van, even better is each individual tire weight measurement. Then calculate how much pressure you should be running. This from an earlier thread:

Old school answer:

The pressure rise from cold tire to hot tire should be 4-6psi. Less than 4psi rise means the cold pressure is too high, more pressure rise means the cold pressure is too low.

Best answer:

Get the actual weights on the tires and ask the manufacturer for the proper pressure for that weight.

My method:

Again, get the actual weight. Compare it to the max weight on the tire. Do some math.


Actual weight/Max weight X Max Pressure = Desired pressure

If you have 2500# on a tire rated at 3000#@80psi you get:

2500/3000 = .8333 .8333 x 80psi 66.66psi, which I round up to 70psi


Then I always round the pressure up. Much better to err on the side of too much pressure than on the side of too little pressure.

As a general rule, D and E rated tires carry the same load at the same pressure. The big difference is E rated tires can handle more pressure, hence more load.

My van weighs in at 9800#, fairly evenly split front/rear side/side. The tires are LT275/70-18E rated at 3640# @ 80psi. For 4 tires, that would add up to 14,560# at 80 psi. My math says I have 9800/14560 of full load. That is about 67% of the max tire ratings. 67% of 80psi is about 55psi. I run 65 psi. A good safety margin. I will never run a tire at its full capacity. Just too much at stake for me.

4 tires rated at 3000# would be too close for me. Going down the road with some lean to the road, the outside tires could be overloaded for many miles. I wouldn't do it. I always want at least a 10% safety factor, 20% is better. Hence, my 65psi in my tires.

I always round up with tire pressures since higher pressures (within the max tire ratings) will reduce tire temps and might tend to wear the center of the tread. Lower tire pressures will cause higher tire temps and can easily cause a tire to fail.

Your RB probably has less weight on the rear than our EB does, hence lower tire pressure on your rear tires.

There should be enough here to confuse the issue. Good luck.

Mike

[flyfisher]

Great information, thanks Mike!