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Old 07-03-2008, 06:45 PM   #1
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E-350 tire PSI??

2008 Ford E-350 Diesel 2X4 RB .... The door jam labels recommend 80 PSI for the rear tires and 55/60 for the front tires. Does one run the recommended pressure or a little less? When I picked it up it was 70 rear and 50 front. Getting ready for a 3-week run to Canada.

Philip

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Old 07-03-2008, 06:46 PM   #2
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What size and rating are the tires?
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Old 07-03-2008, 06:53 PM   #3
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Old 07-03-2008, 07:46 PM   #4
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The factory tire pressures are based on the van being fully loaded. Either you can weigh the van to determine the weights on the front and rear or you can guess. More weight needs more pressure.

Your stock tires are rated at 3042# @ 80psi. You can derate that linearly.
38#/psi. The tires will support some weight at 0psi, but linear is close enough.

Since the rear axle has two tires, it can support 6084# at 80psi. If your rear axle weighed 4000#, it would take 52psi to support that weight.

If the van were empty and weighed 3800# front and rear you could run 50/50 for tire pressures.

An old trick was to measure the tire pressure then drive at highway speeds with the load you want to use. Then after and hour measure the hot tire pressures. If the pressure went up more than 6 psi, your pressure was too low. If the pressure went up less than 3 psi, your pressure was too high.

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Old 07-03-2008, 10:08 PM   #5
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My driver's side door jamb has a van weight and recommended tire pressure sticker added by SMB.

Do not base the tire pressure on the maximum recommended tire pressure on the side of the tire, but of course, do not exceed that tire pressure.


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Old 07-07-2008, 10:01 PM   #6
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The key to this whole thing is to check the MAX COLD PRESSURE on the sidewall of the tire. Use that and the weight of your van to determine the appropriate range of tire pressure.

Tires get changed and the door jam sticker may not.

Check the tire sidewall.

I have not even looked at the door sticker on our 2008. Our 35in E-rated tires have a max pressure of 65 or 66psi.
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Old 07-28-2008, 01:36 PM   #7
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Mike, thanks for the really helpful information. Are there any advantages/disadvantages to running the tires at a higher PSI than the formula supplied in your post? My new tires are rated for 3750 lbs at 80 psi. The weights on my door jamb are 4400 lbs (front) and 6084 lbs (rear). Using the formula, it says I should be running the fronts at approximately 47 psi and the rears at 65 psi.
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Old 07-28-2008, 01:48 PM   #8
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Quote:
Originally Posted by sdwindansea
Are there any advantages/disadvantages to running the tires at a higher PSI than the formula supplied in your post?
Yes, and I'm sorry I forgot to mention it.

Lower pressures generate more flex and more friction in the tire. That lowers your mileage (fuel and tire) and makes heat - heat that can damage or kill a tire (and passengers - remember the Ford/Firestone fiasco).

Higher pressures are the opposite of above. Higher pressures tend to make a harder ride, but better on road handling.

I tend to run 15% above the calculated numbers as a safety factor. But, never exceed the max ratings on the tire sidewall.

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