New tires, new pressures too?
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Joined: Mar 2009
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From: Puyallup, WA
New tires, new pressures too?
So I am a motorcycle mechanic by trade and no mater what tires we put on someones bike we always set them at the tire pressures the manufacture suggests. Now a couple weeks ago I bought a set of goodyear wrangler Duratrac tires in a 285/75-20 size which is a slightly larger than stock on my 06 f-150 supercab. The ford dealer that installed them is now suggesting that I run them at 60psi which is almost double the 35psi that ford says they should be at with the stock tires. I tried finding the info on goodyears website and the only info I could find was to run what the manufacture has on the sticker in the door jam but I'm guessing that may not apply if you have a larger tire. Maybe its more if the tire has a higher load rating? Or maybe because it is a more aggressive tire? Just looking for a little reason to their rhyme here. I don't want them to wear too quickly because the pressure is too high.
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Joined: Dec 2003
Posts: 6,550
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From: Mount Airy,MD
Everything depend upon load range and rating, not size. If the recommended pressure for the OE tires was 35, that was a p series (passenger car) tire. If the tire you purchased was an LT (light truck), it would come in different "flavors" also. They would be a LR C tire with a max of 50 psi, a LR D tire with a max of 50 psi, a LR D tire with a max of 65, a LR E with a max of 65, or a LR E with a max of 80. Each would probably require a different pressure for your particular vehicle.
A good place to start for each is:
LR C max 50 - use 40-45 - don't go below 38
LR D max 50 - use 40-45 - don't go below 38
LR D max 65 - use 45 - don't go below 40
LR E max 65 - use 45 - don't go below 40
LR E max 80 - use 50 - don't go below 45
Each tire will be different. I have seen LR E max 80 tires with such a high load rating that 40 would have been safe.
You can use a number of about 2000lb per tire as the rear axle is rated to about 4000lbs.
In your case, the specs of the tire is 3640lbs at 80 psi, so 45-50 will be fine for that tire.
A good place to start for each is:
LR C max 50 - use 40-45 - don't go below 38
LR D max 50 - use 40-45 - don't go below 38
LR D max 65 - use 45 - don't go below 40
LR E max 65 - use 45 - don't go below 40
LR E max 80 - use 50 - don't go below 45
Each tire will be different. I have seen LR E max 80 tires with such a high load rating that 40 would have been safe.
You can use a number of about 2000lb per tire as the rear axle is rated to about 4000lbs.
In your case, the specs of the tire is 3640lbs at 80 psi, so 45-50 will be fine for that tire.
Last edited by kingfish51; Nov 8, 2010 at 11:43 AM.
