Air Pressure in 255's

[Suty]

OK, I got my 255's today ,paid 130 apiece at Discount Tire (Americas Tire ou West) I really think I am going to like these. I was wondering what kind of Air Pressure you guy's are running? Unloaded and for around town. Thanks for all the Help around here and the great Idea's. Tu Compadre, Suty

 

[Scott Brady]

38 PSI, front and rear. It came from a load chart somewhere, but I cant find it right now.

You are probably a little lighter, so maybe 34-36 psi?

These tires are load range E, so they will run pretty cool at that pressure.

 

[erin]

I run mine at 32psi with good even contact patch, though any lower and I get more outside edge lug noise.

Scott, what pressure do you run offroad?

 

[pangaea]

My truck's a bit heavier than scotts, so I run tire pressures accordingly. Usually, I've got 42psi F/R on road. Off road, I usually air down to about 18psi but I'll go lower if the terrain demands it (ie really soft sand, etc)

 

[Brian McVickers]

Nathan,
Do you have bead lockers, or LR wheels?
I have LR alloy wheels and have not gone below 20psi for fear of popping a bead. How low can I go with LR wheels?

Suty - congrats on the new shoes!
What brand / model tires did you get?

 

[Suty]

Nathan,
Do you have bead lockers, or LR wheels?
I have LR alloy wheels and have not gone below 20psi for fear of popping a bead. How low can I go with LR wheels?

Suty - congrats on the new shoes!
What brand / model tires did you get?

Thanks, I got BFG M/T, Paid 130 a piece. Tu Compa, Suty

 

[goodtimes]

If you are not sure what pressure to run your tires at (different size than OE, different brand, different load rating, different vehicle weight, etc), I suggest doing a "chalk" test. Take a piece of chalk and make a 1" wide line across the tread of one front and one rear tire (sidewall to sidewall). Drive around the block, and inspect the line. The line should "wear" evenly all the way across the face of the tire. If the middle wears more than the outside, lower the pressure a couple pounds, and repeat the test.

In my jeep wrangler, I run 33psi on the street, with a D rated tire. Off road, it is more of a "feel". In my jeep, I am happy at 10psi, and start getting nervous at 8psi. In my dodge, I probably won't get much lower than 20psi, and even that is probably too low for a 6500 pound rig (that is, 6500 pounds dry. By the time it is outfitted, it will be closer to 8500 pounds).

 

[Scott Brady]

I run mine at 32psi with good even contact patch, though any lower and I get more outside edge lug noise.

Scott, what pressure do you run offroad?

On the trails I run, traction is rarely the problem (long wheelbase and f&r lockers), so I air down for ride comfort. I almost always air down to 22. But, for rock crawling and sand, I will air down to 16-18 psi.

On the Jeep, I go down to 12.

 

[Jonathan Hanson]

I run my BFG 255/85 MTs at 96 pounds front and rear. With this pressure my FJ40 will pull .92 Gs on a 100-foot skidpad, slightly better than a Lotus Elise.


Just kidding. 38 pounds front and rear seems to work well on an old FJ40. The 255s seem to roll smoothly over a lot of debris that I could feel through 235/85s.

 

[Scott Brady]

Lotus Elise.
.

Nice car... :bowdown: I dont fit in it though, bummer

 

[pangaea]

Nathan,
Do you have bead lockers, or LR wheels?
I have LR alloy wheels and have not gone below 20psi for fear of popping a bead. How low can I go with LR wheels?

I've got the Defender/Series steel wheels on my truck right now, but I ran for a couple of years with the alloys as well.

LR wheels seem to be pretty resistant to losing a bead, compared to most other non-beadlocked wheels out there. I'd say you could safely go down to 15 psi without loosing a bead, anything lower and you're gambling a bit. On my old Defender, I used to go down to 12 psi quite regularly.

Just make sure that you have an on board air source with pressures that low. I sure wouldn't want to drive down the highway with that little pressure in the tires.

 

[Redline]

Lower PSI for 255s

http://www.expeditionportal.com/forum/showthread.php?t=8619

I found this thread from a link provided by Pierre in the thread above...

I'm surprised at some of the higher pressures mentioned here. I know that tires will generally run cooler at higher PSI, and overinflation worries are less with modern radial tires, but I generally prefer to run "enough" PSI but rarely much extra.

Below, 255/85 PSI pressures for the load are for single wheel applications from 35-65 PSI in 5-PSI increments.

LT255/85R16
1920 2110 2290 2470(C) 2635 2800 3000(D)

At 35-PSI a 255/85 will carry 1,920-lbs per tire, 3,840-lbs per axle, and 7,680-lbs per vehicle. That's a lot of capacity for most of our trucks. Obviously if your highway speeds are higher you may want to run more pressure, but in most cases 35-psi should provide that buffer and then some.

In my fairly heavy 4Runner (5,440-lbs unladen) I've recently been running 32-psi, the recommended PSI for the stock tires. I have also played with pressures from 30 or 35 PSI.

In my '96 F350 diesel, when unladen, I usually run 30-35 PSI in the rear (with a rear axle weight of slightly less than 3,000-lbs) and 44-psi in the front with 4,300-lbs on the front axle. I increase my PSI when carrying more weight, but when empty it is not needed. I believe ride and traction are better at these lower pressures and wear has not suffered. Back in 1998 when I was driving my then new F350 more conservatively, my first set of Multi-Mile (Les Schwab) TXRs in 255/85R16 were going to last over 60,000-miles if I would have chosen to use them until 2/32.

Load-range-D 255/85 tires seem to be less sensitive to riding poorly when slightly over-inflated compared to stiffer, E-Range tires.

 

[Willman]

I run mine at 35 psi.

works great and wears even.

 

[jim65wagon]

I run 38 in the front and 34 in the rear daily.

 

[p1michaud]

Tire pressures

When I get home I'll try to do the "chalk" test but at this time of year the challenge becomes finding a dry parking lot or road. Everything is covered in snow or ice at the moment.

I've got them set at 36 psi for now and will do a bit of testing when I get home. I've read about anohter method of verifying that you have the correct pressure. I can't find the post right now, but it was roughly as follows.

1. Set and record tire pressure when cold (i.e. 30 psi)
2. Go for a minimum 5 minute drive to warm up the tire.
3. Re-measure pressure. It should be less than 5% over your original value (i.e. 1.5 psi for a starting value of 30 psi as per above example). Here is the catch, if the pressure was more than 5% greater you need to inflate your tires a bit more.
4. Repeat this process untill the difference between hot and cold is less than 5%

The theory is that if you tires are under inflated they heat up causing the pressure to increase. Anything over a 5% increase is too much. Some tire design engineer had written this up. I'll see if I can find the post or link later.

Cheers,
P