Well I finally got my 285/70/17 BFG A/T KOs put on Friday and they're great! Much improved look from the 265s and would like to thank ross2388 and hawg_man for the pics also. I checked the tire pressure today and they are showing in the neighborhood of 60 psi (my tire gauge only goes to 50). I know the tires say on the sidewall that they can handle 65 psi, and the sticker in the door says 35 psi for the stock 265s which is what I used to run in my other tires. My question is is it safe to run that much pressure and will the middle of the tread wear out quicker and what do you recommend? At 35 psi, my other tires wore pretty evenly. I just didn't know if the pressure should change with a bigger tire size...

 

The max psi listed on the sidewall is for towing/hauling heavy loads, not daily driving. I've found 40psi works great for me in truck tires.

 

It will wear out quicker, and you do not need to run that high. If they are load range D I would run around 45. If load range E, use between 45-50. I only have experience with the LR Es that have a max of 80. Always ran them at 50. That should get you decent wear and ride without compromising safety at all with a too low pressure. As always, keep an eye out for excessive wear. You can adjust down a little from the numbers I gave you, but I wouldn't go more than 4-5 pounds lower. And you probably will not need to.

 

I actaully called BFG about this. I have the same tire as you dou but in a 265/70/17. If you call them they will recommend a pressure based on your vehicle and what tires were on it when it came off the assembly line. The rule of thumb as they explained it is, whatever the reccommended tire pressure is on your door (typically is 35 psi) that Ford recommends, is Ford basically saying, for the amount of weight on your tires with the truck unloaded the tire pressure should be 35psi for your best overall performance and tire wear.

For, example, my stock General Americraps, were 255/70/17 they have a max rating of 2337 lbs at 44 psi. This translates to 53.11 lbs of weight for every psi. My new BFG's have a max rating of 2470lbs at 50 psi. This translates to 49.4 lbs of weight for every psi.

Ford recommends that the 255/70/17 Generals be at 35 psi at normal driving conditions. If you take 53.11lbs/psi and multiply that by the recommended 35 psi you get 1858.85 lbs. This is what ford says is "ok".

So now for my new tires (BFG's) I need to run a pressure to equal that rating if I want to follow Ford's recommendations. As mentioned before, the BFG's handle 49.4 lbs of weight for every psi. So now I can take the 1858.85lbs and divide that by 49.4lbs. This equals 37.63 lbs. This tells me I can run my BFG's at 38 psi and be within the Ford recommendations.

Now take that same theory and apply it to the 285's. The 285's (assuming they are a load range D) have a max rating of 3195 lbs at 65psi meaning they can handle 49.15 lbs of weight for every psi. Take the 1858.85 divide that by 49.15 you get 37.82. So at the minimum tire pressure you should run to stay with in Ford door panel recommendations is 38 psi.

So bottom line, keep them at 38 psi minimum and adjust up to fit your comfort level. I don't like the ride I get if I run anything under 40 psi, but that's just a personal preference. Hope this helps

 

They are, in fact, load range D. Thanks for the advice. I'll lower them to 40-45 and see how that goes. I didn't think to check right after I got them put on but glad I thought about it today. I know the guy who put them on really well, but don't know why they put the max pressure in the tires. I just knew it wasn't right when my tire gauge maxed out, oh well, thanks again guys...

 

Nice work with the math skills, slash! Yeah, you guys are all thinking along the same line as far as psi goes, so I'll definitely be adjusting that pressure asap. Thanks again guys...

 

So what would you reccomend for LT285/65/18 Nitto Grapplers (load range E). On the tire it says 80 max psi with no recommended psi. Im currently running them at 50 psi. I only use the truck as a day to day driver. What should I keep the psi at to have the best wear and ride?

 

i keep mine around 40 all around and they are wearing good.

 

50 is fine. I had a set of BFG All Terrains in LR E on for 40+k. Still had tread when I traded the truck.

 

Load range "D" 42 to 45 for everyday use, I go up to 48 to 50 on long trips in the summer for a little better mileage and help against getting a blowout. Only because I had a blowout once on an under-inflated tire.

 

If you stick to that rule of thumb your tires would need to be at 40-42 psi to be within ford recommendations.

 

yeah, i dropped them to 42-43 psi this morning and drove about 120 miles today. the ride seemed to be better too compared to the exact same trip saturday.

 

I know this is very old, but damn was it helpful! Thanks and a bump for others.

 

Totally incorrect. If your vehicle came with a LR C Ford would recommend at a minimum 40 psi. That was in 2004. Ford now recommends 45 psi. The 35 is for a p series only. It requires it to be at max for an F150. A p series gets all it's load carrying ability at 35 psi. Anything above that if it is rated to 44 is for sidewall stability only. It does not increase load carrying ability. That is why Ford recommends 35 on a p series.
If a LR E with a max of 80, came on the current F150, with TPMS. That system would give you a low pressure warning at 46 psi.

http://www.nhtsa.gov/cars/rules/ruli...ule.html?name=

 

Been running 45 PSI in mine, have 40k on them and still have at least another year on them, great tires except next time I'm going to get them siped.