Air pressure

[utahred]

My wife and I have RV'd for over 10 years, but we're bright green when it comes to off-roading. I've pulled our 5th wheel over 90 thousand miles on paved roads with a TWD Ford 350. However, the Ford doesn't like the soft stuff. I've taken it off road a few times, and got it stuck once, resulting in a $90.00 tow charge. On other occasions, I've just missed getting bogged down.

We wanted to get into the back country, but the Ford isn't a good choice, so we picked up a 2005 4x4 Xterra for off road excursions. I didn't know much about RVing to begin with and, now, I'm in a similar spot with off road driving and could use a wee bit of advice.

This question has to do with airing down.

Should I air down only for sand, or as soon as I leave the pavement? For example, my wife and I will be traveling from St. George Utah to Tuweep around the 26th of this month. I've driven on washboard roads without airing down many times, but I've read somewhere that lower tire pressure makes the ride a bit smoother, without damaging the tires. My tires are Toyo At's and the dealer recommended 20psi for sand.

I bought a 12volt Viair portable compressor to re-air with, so that's not a problem.

Any advice will be appreciated.

 

[XterraVT]

I've run BFG A/Ts for a few years on my X and air down to 18psi for trail riding.

The lower the pressure the larger the foot print But if you go too low you will risk blowing the tire bead.

20psi is pretty good for dirt/ gravel roads and I would probably go down to 18psi in the sand.

If you are going to be on a dirt road for an extended period of time I would air down. You will get a smoother ride and better grip on the trail than with a full tire.
You will want to be careful at speeds with an aired down tire as pot holes like to eat these tires more ( less air gives you a softer tire. This compresses easier and could be damaged by pinching the tire against the rim ). Not that you are speeding down a wash board section but keep it in mind as you travel.

You will also want to air back up before hitting highway speeds. The aired down tires will roll more side to side and could cause you to loose control.

I hope this helped you out a little.

Enjoy the X and where it will take you.

 

[utahred]

Yes, that's the kind of info I was looking for. It's always an advantage to have some knowledge of what to expect before proceeding.

I hadn't tried the Viair before this afternoon, but it works very fast. Pumping the tires up before going back on to a hard surface won't take much time at all.

I've assembled a pile of recovery equipment, and intend to practice in my driveway tomorrow, if it doesn't rain. I won't be using a winch to begin with; I'll go with a Pull Pal and the Hi-Lift.

No doubt, I will have more questions.

Thanks.

 

[RonapRhys]

There's definitely a difference. I've got the BFG AT KOs on there and you'll honestly see a huge difference in capability with your aftermarket tires over what they put on there stock. Even though I've got an OR version (which comes with a locker), mud was always bothersome until I upgraded the tires.

Air down, go slow, and enjoy it out there.

 

[gwittman]

I know a lot of people like to air down as soon as they hit the dirt. I have done a lot of off-roading with a 73 FJ55 and a couple different Ford Rangers since 1977 and I usually only air down when I need to. I like to keep the side walls fairly stiff to help keep them from getting damaged by sharp rocks. If I come to an area that I feel I need to air down (like a long, soft, sandy area) I will air down to around 20 psi and leave it there until I come to a rocky section again or back on the highway.

I have used mostly BFG AT tires but am currently using Procomp MT tires for off-road adventures.

 

[mitssan]

I ran Toyo AT's on my 07 frontier for two years. I did a lot of fire road with the truck and never aired down. I did however air down for anything more agressive than fire road. For me I was worried about side wall damage and tire wear.

The Toyo's only have a two ply side wall compared to the three ply on the BFG.

Ulrimatly it comes down to preference. How soft do you want the ride vs how long you want the tires to last.

The toyo's also have more scyping than the bfg so they tend to hold rocks, that will eventually end up causing a puncture. I'd recommend checking the tread after a weekend of driving and making sure you aren't packing a sharp rock into the tread.

Cheers
Maurie

 

[alexrex20]

i air down to 17-20psi if i plan to do any wheeling. if it's just some graded dirt road, i leave it at 35psi (my highway pressure). on the really soft sand beaches, i air down to 12-13psi. just don't do any aggressive driving (high speed cornering, drifting, donuts, etc.) and you won't blow a bead. i don't know what the beaches are like where you live, but 20psi might be fine.

at 12-13psi though, it rides smooth as butter and is virtually impossible to get stuck.

 

[matt s]

There is a quote floating around this forum somewhere that I took to heart for gravel roads etc.

"Your tires should be doing half the work of the suspension."

I go down to 20 to 25 and the difference in ride is incredible.

 

[michaelgroves]

"Your tires should be doing half the work of the suspension."

Why?

The suspension is designed to soak up the bumps. And tyres are not designed to run at low pressures. I would agree that for washboard, it's sensible to keep the tyres at the low side of normal pressures, but no tyre manufacturer (or car maufacturer) would recommend running at 20psi, except lightly laden, for short distances, at low speeds.

Very few things skrik me more than the idea of a heavily laden expedition vehicle travelling hundreds of miles of washboard at 60mph with seriously underinflated tyres. All because "travelling fast, and having soft tyres gives a much better ride".

In fairness, you never said anything about high speed, or long distances, or heavy loads. But I thought I should

 

[utahred]

Thanks, this has been a very helpful discussion for me.

A softer ride would be helpful; washboard roads rattle my tiny brain and make me irritable as hell.

I never drive more that 35 on rough roads so speed shouldn't be an issue, but on the other hand, I wouldn't want to shorten tire life too much.

This next trip I'll drive a bit with 35psi in the tires and then air down to 20 and see if I can tell the difference.

Where I grew up in New Mexico, off highway roads are mostly sand and gravel. In Utah, the underlying rock formations make for potential tire busting sections of bare rock. Although I had a BFG tire guy tell me once that tires will take almost any punishment if you keep the speed under 30 mph.

 

[matt s]

Why?

The suspension is designed to soak up the bumps. And tyres are not designed to run at low pressures. I would agree that for washboard, it's sensible to keep the tyres at the low side of normal pressures, but no tyre manufacturer (or car maufacturer) would recommend running at 20psi, except lightly laden, for short distances, at low speeds.

Very few things skrik me more than the idea of a heavily laden expedition vehicle travelling hundreds of miles of washboard at 60mph with seriously underinflated tyres. All because "travelling fast, and having soft tyres gives a much better ride".

In fairness, you never said anything about high speed, or long distances, or heavy loads. But I thought I should

Fair enough, safety first.:sombrero: But yes I never said heavy, speed, etc.

I should also mention that the idea and quote are not mine. However I have embraced the idea so I guess that's guilt by association.

As to heavy, well the heavy stiff suspensions required to carry those heavy laden vehicles don't give much on wash board. Mine will rattle your teeth out in about 3 miles. Aired down it's smooth and the suspension handles the big bumps just like it's supposed to. It's like having two suspensions for two different tasks.

As to speed, no not me, when aired down I run 30mph tops. The whole point is to see and experience the trail right? Not blow through in a cloud of dust.

While no manufacture would ever tell you anything other than running at perfect PSI due to liability, airing down is a pretty proven method of gaining ride and traction. Also airing down to 20 or 25 psi is not even close to the same thing as the guys airing down to 10. At 20 the chances for bead blow out and tire damage are not that high (provided speed is reasonable).

 

[JIMBO]

:sombrero: It's weird, I never air down my X/jeep, for off-road unless it's DEEP snow, or DEEP sand, however

I do air down my trailer for washboard roads (long) and I have adj shocks for my jeep, so I've set them real lite for washboard and 15/20 mph

:costumed-smiley-007:costumed-smiley-007 JIMBO

 

[RonapRhys]

:sombrero: It's weird, I never air down my X/jeep, for off-road unless it's DEEP snow, or DEEP sand, however

I do air down my trailer for washboard roads (long) and I have adj shocks for my jeep, so I've set them real lite for washboard and 15/20 mph

:costumed-smiley-007:costumed-smiley-007 JIMBO

I think there's a difference in airing down based on the conditions you normally encounter. I almost always air down, but up here we do get deep mud, clay, etc., so it's pretty advisable. If it was nothing but pure rocks or not particularly muddy I'd probably not bother too much. I won't air down unless it was something where I was going to be there for some time - mostly because my air compressor would likely take 3 hours to air back up.

 

[Frankspinz]

There are so many variables. My recommendation is : experiment ! This spring I installed my first set of BFG AT's on a 2003 Xterra. These tires have a stiff sidewall and my Xterra isn't so heavy to push these tires to the limit. I can air down to 20psi and barely see the difference.

I recommend airing down in any circumstance you can air back up before hitting the highway. How much to air down depends on your tire & your vehicle load, so : experiment !