Tire Pressure

[brett13]

I've been through parts of Beef Basin and gone from Moab over Hurrah Pass to Catacomb rock, which I think is at the edge of Lockhart Basin. That is some of the coolest terrain around, like being in a crater on the moon or something (queue the Pink Floyd). Only two places I know of to get gas on that route- if you diverted from Beef Basin into Monticello and the private campground just outside Needles($5/gal) about 2 mi from Elephant Hill. That's it. For those who haven't been there, even Hurrah Pass is knarly in a full size p/u as the trail is tight. Down lower, near the bottom, you will pitch and roll a lot.

 

[SDJeff]

Hello,

I recently got my Hawk on a new F250 and swapped out the factory tires with some E rated BFG AT's. The tire shop set the pressure at 75 in the front and 80 in the back. This seemed really high to me as I had read this thread and b/c the MAX recommended for the tires is 80. When I asked them, they said this is the pressure specified by Ford on the door well (true) and that they did not want to do anything contrary to Ford. I asked the dealer and at first the guy said "ask Ford". When I said "you are Ford" he said that is what the design calls for. I would go ahead and reduce the tire pressure, but the truck has the sensor that will probably come on if the pressure is lower than what it is set for. I saw the various pressure reccs you all previously gave on this thread for E rated tires. Any reason to think the pressure should be higher on a camper laden 2011 F250? I assume the engineers had something in mind, but it seems hard to believe that it should be this high. Also, the sticker on the door that specs 75/80 doesn't differentiate between loaded and unloaded. I am confused, but think the pressure should be lower. Thoughts?

 

[telebrewer]

Hello,

I recently got my Hawk on a new F250 and swapped out the factory tires with some E rated BFG AT's. The tire shop set the pressure at 75 in the front and 80 in the back. This seemed really high to me as I had read this thread and b/c the MAX recommended for the tires is 80. When I asked them, they said this is the pressure specified by Ford on the door well (true) and that they did not want to do anything contrary to Ford. I asked the dealer and at first the guy said "ask Ford". When I said "you are Ford" he said that is what the design calls for. I would go ahead and reduce the tire pressure, but the truck has the sensor that will probably come on if the pressure is lower than what it is set for. I saw the various pressure reccs you all previously gave on this thread for E rated tires. Any reason to think the pressure should be higher on a camper laden 2011 F250? I assume the engineers had something in mind, but it seems hard to believe that it should be this high. Also, the sticker on the door that specs 75/80 doesn't differentiate between loaded and unloaded. I am confused, but think the pressure should be lower. Thoughts?


I think people get too caught up with what the tire says or what the door sticker says. I have BFG AT's, load range E. Unloaded I run 60 psi. in the rear and 55 psi. in front. Sometimes that seems too high. Over time watch your tire wear. If the center is wearing faster, you have too much pressure. Depending on your load when traveling, the heavier you are, the more more pres. I think at your most heaviest, 80 psi. I really try to get the most out of my All Terrain TA's and the most common thing I see if over inflation.

 

[Cort]

one easy test to do on a weekend when you have some time is to spread marking chalk on your front and rear tires. Make sure you go past the tread and a little down the side wall. Then take it for a drive and see where the chalk wears off. That will show you what your contact patch is. If you are over inflated you will only wear the chalk off the center of your tread. If you are under inflated you will wear the chalk off all of your tread and some off a bit of the side wall.

take a look at the weight rating of your E-rated tires....its huge. The only time to be a maximum pressure would be a fully loaded 1-ton.

Over inflation is the most common problem I see as well.

On my Tacoma I am currently running 30 rear/35 front when empty and 50-65 rear/45-55 front when fully loaded with the camper.

Cort

 

[brianjwilson]

The PSI rating on the door jamb is for the factory tires at GVWR or Axle weight ratings. For a designated load rating index, there is an inflation chart that specifies the PSI for a specific load. The PSI on the door jamb, again, is for a stock tire with max load. The tires do not need to be at MAX PSI unloaded unless you are running max load on those tires.


Click on the Load & Inflation Table Application Guide on this website if you are interested in reading more.
http://toyotires.com/tire-care-safety/load-inflation-tables

 

[Lighthawk]

Click on the Load & Inflation Table Application Guide on this website if you are interested in reading more.
http://toyotires.com/tire-care-safety/load-inflation-tables
[/quote]

Thanks for the straight info, Brian. I've been pondering this since I put on a set of BFG AT's on my non-stock 18" wheels. Sure I can crank em up to 80 psi, but that's abusive (to the driver) when unloaded. I checked my 06 Tundra for tire sticker info and it states stock tire size of P265/70R16 which are O.E. tire pressure of 29/30 psi F/R. Translating that roughly via the tables on the link you provided I get 2216# load capacity with stock, then applying that against my LT265/65R 18 I come up with a unloaded tire pressure of roughly somewhere between 40-45 psi. I say roughly since I do not find my exact BFG tire size on the Toyo chart and the load range falls between 40 and 45 psi. They have 275/65 and I have 265/65, so I suppose that's slightly taller tire.

Good enough for gov't work! I've been running 35 psi all around since airing down last week to play in the nearby gravel pit and it's been very comfortable and sticky, but I could see that bumping up to 40+ psi could improve the mileage a bit. Fortunately I live and work in a small town and don't roll many miles between WTW ventures .

Adding a thousand pounds for my loaded FWC Hawk, and assuming equal weight distribution, I would figure ~2500+ lbs. per wheel (O.E. rating of 2216 + 250). According to the Toyo Load Inflation Table that bumps the recommended tire pressure to ~50psi. I suppose many of you will say the Hawk (dry @ 900#) + water, food, black labrador, etc. will likely weigh a heck of a lot more than 1000#, so 50psi looks minimal, and certainly more weight is on the rear axle. If we assume all of the 1000# is on the rear and go with 2700#, then the recommended tire pressure is 55psi rear. FWIW, I ran 60psi on our last highway run to DV and then aired down to 20-25psi for the dirt. But I'm still a novice figuring this all out. Thanks again for the info, Brian.

 

[SDJeff]

Thanks for all the good info everyone.

 

[AZHawk]

I'm late to this dance, but there is another concern I have, and that is running low pressure on roads like we have in the SW where there are sharp chert nodules or rough limestone or basalt. I'm afraid that running low pressure will lower the sidewall on the sharp stuff and cause a tear. On these roads I air up. The pictures I see in this thread are on rough roads but not the kind I'm talking about that tear up tires. I agree that speed is a factor as well, but I would rather have tread on the ground on some roads than the weaker sidewalls.

 

[David_h]

I'm late to this dance, but there is another concern I have, and that is running low pressure on roads like we have in the SW where there are sharp chert nodules or rough limestone or basalt. I'm afraid that running low pressure will lower the sidewall on the sharp stuff and cause a tear. On these roads I air up. The pictures I see in this thread are on rough roads but not the kind I'm talking about that tear up tires. I agree that speed is a factor as well, but I would rather have tread on the ground on some roads than the weaker sidewalls.



Last year's spring break found us in Death Valley on some of those wash board roads; really bad. THis spring break I'm going to try airing down a bit unless the rocks look really sharp edged. On the way to Racetrack playa I remember passing at least two SUV types with blown out 'C' range stock tires. They were left on the side of the road, so mayber their spares were shot to. The Death Valley road north toward Big Pine was really bad washboard.
Dave H
Mill Valley, CA
06 Hawk on 05 F150 4x4