Airing Down Tires

[Tentsontop]

My daughter and I joined a gaggle of 40s, one other 80 with a lift, a 78 40 body on a 96 chassis, a Prerunner and a 60. Most everybody aired down, but I didn't because: 1 I didn't have anything to bleed off air or any means of airing back up and 2 the trail wasn't that bad and I didn't see the need.

Anyway, I'm running 265 75 16 BFG Rugged Terrains @ 50lbs w/6k on them. I ran most of the trail in low with the CDL and Rear lockers locked. All was good until we came up on ice and slushy snow. Even with all four wheels locked I spun where everyone else just slogged through.

What I want to know is does airing down make that big a difference or should I be looking for some new BFG ATs? The other 80 aired down his ATs and made it through w/out lockers.

 

[spressomon]

My daughter and I joined a gaggle of 40s, one other 80 with a lift, a 78 40 body on a 96 chassis, a Prerunner and a 60. Most everybody aired down, but I didn't because: 1 I didn't have anything to bleed off air or any means of airing back up and 2 the trail wasn't that bad and I didn't see the need.

Anyway, I'm running 265 75 16 BFG Rugged Terrains @ 50lbs w/6k on them. I ran most of the trail in low with the CDL and Rear lockers locked. All was good until we came up on ice and slushy snow. Even with all four wheels locked I spun where everyone else just slogged through.

What I want to know is does airing down make that big a difference or should I be looking for some new BFG ATs? The other 80 aired down his ATs and made it through w/out lockers.

Both: Good tread certainly helps for snow/ice and also PSI has to be lower than your 50psi...regardless of what tires you have. I generally (285R75/16 MT/R) get around really well with 35psi even on snow. If the conditions are particularly challenging (snow/ice) I air down to 25psi.

 

[Vitesse_6]

I dont see whay you couldnt air down to 20-25 psi. Im sure if you asked someone would have a way for you to air up before hitting the road, I know when we (WasatchCruisers) head out there are at least 6-7 people with a way to air up, Even if its using a $20.00 ciggie lighter one its better than nothing.
Good luck

 

[tarbe]

I am not familiar with those tires, but I am willing to bet that if you had been down to 20 lbs or maybe a little less, you would have seen a great difference in your traction.

You were riding on a very small contact patch, with very high pressure at the interface. You know what happens under a skate blade, right? Instant ice water under your tires. Terrible for traction

I may be exaggerating a bit, but your trouble was most likely pressure induced.

 

[desertdude]

HERE is an interesting read on tires and airing down

 

[MoJ]

You could very likely get away with 20lbs but I would bet that that is only part of your issue. The second part is that the BFG Rugged Terrains are not very aggessive, certainly not on par with the BFG A/T. Not saying you need to go out and spend the money for new tires - it all depends on what you want to do. If you are otherwise happy with the tires than spend some time experimenting with air pressure. If you're still not happy than tires may be in your future.

 

[LandyLover]

A guy I know got his HJ62 stuck in some deep snow 2 weekends ago. He had 33" Grapplers with open diffs and a 4" lift and he did pretty good job in getting himself stuck up to his frame... My 80 with 32" 50 psi BFG A/Ts with diffs locked could not make it up one section because I kept digging holes. The grade was around 15%. I aired down to 16PSI front and back and I walked up without any wonders if Id become really stuck. What a difference. BTW, the BFG ATs have triple sidewall - stiffer- so I feel no hesitancy in lowering even more than 16PSI...

Moral of the story: Lower airpressure = larger footprint the tire makes on the ground.

2nd moral of the story: Get a good under hood air compressor because youèll use it for more than just airing up your tires.


Cheers.

 

[Tentsontop]

Next time I'll try airing down to 20 psi or so. There was one sandy rock section that the other 80 spun a little on that I happened to slip through without a problem. I think I'll look into a compressor as well. I don't go off-road that often, but I'm sure it will come in handy at the lake he, he,he.

 

[NorCalDoug]

it's sort of like swimming (freestyle) with your hands perpendicular to the water -- sort of like karate-chopping on every stroke rather than with your hands parallel to the surface, scooping water as you go.


It's amazing the difference airing down makes when off-road.

 

[e9999]

I would think a good compromise might be somewhere between 20 and 30 psi. Way better traction wise than 50 I would guess, and you can still drive on asphalt OK in a pinch (maybe not at 100 mph on the freeway though) if you can't air up. I'm just carrying the little MV50 compressor all the time. Works great and inexpensive, and sure is easier to carry around than my CO2 tank and reg.

OTOH, it may be overkill to do most of the trail with the rear locked unless it's a pretty serious trail. Today I did a bunch of steep dirt and loose shale/gravel hills and I did fine somewhere between 30 and 40 psi with the MT/Rs, FWIW. Only had to lock up once and that was cuz I didn't want to take a chance on sliding down the mountain... No snow, though...

 

[Mr.Iceland]

when driving in arctic conditions..

hi there I just wanted to add a point for you guys just for fun. In Iceland when we are driving in snow, I know it is not mixed trail\snow, only snow. we go as low as 2 psi on 38" and 1-1.5 psi on 44" tires. so yes, definetly lower airpressure in snow helps, helps alot

 

[e9999]

hi there I just wanted to add a point for you guys just for fun. In Iceland when we are driving in snow, I know it is not mixed trail\snow, only snow. we go as low as 2 psi on 38" and 1-1.5 psi on 44" tires. so yes, definetly lower airpressure in snow helps, helps alot

wow! that is low indeed! this is with beadlocks, I imagine?

 

[Mr.Iceland]

yes and no

recently most of the guys in rough riding who need to go that low have dedlocks but before they came to Iceland guys just welded an extra edge just inside were the ring of the tire sits on the wheel, this was enough for it to hold on, most of the times
going that low is almost only done in really really deep snow where you have to get on top of it not trew it.

here are a couple of pictures just for fun....

 

[notyourmomslx450]

I went out today in some pretty loose sand, and ran at 15 psi. This is w/ 315s and stock wheels. I did ALMOST pop a bead trying to make a hard cut on a downhill, but it was okay for the most part, and made a huge difference. I think next time I'll be running somewhere north of 15, south of 20

 

[wileetoyote]

I run 33's on both my 4Runner and my '96 FZJ. When in the LC, I drop from 40psi to 20-25psi depending on my load. Even at 20psi, I'll drive home usually on highways or even freeways. Truck feels a little loose so I'll take turns a little slower but straight lines I have no issue driving 70mph. The difference in traction is huge although if packed snow ices over around 4pm (after it melts in the sun but freezes when its getting dark), you can forget it...I once slid backwards down a hill for 150', plowed into an embankment, then watched as my buddy starting sliding backwards towards me (missed me by that much!)

With the much lighter weight 4 Runner, I drop it down to 13psi and use a portable 12 gal tank that I charge at home before I leave to 110psi. When I'm done wheeling, it'll air all 4 tires back up to 20-25 psi at which time I'll drive that home. the tank cost me less than $20 8 yrs ago at Kmart in their automotive section. not sure what they go for now.

I have ARB's on my 4Runner but honestly, after a long day on the trail the last thing I want to do is air back up using a compressor as they take forever...the tank will air all 4 tires back to 20-25psi in less than 5 minutes which is usually what it takes someone to air one tire up to 30-35 psi.

The best setup I've had was on my toy truck before I sold it (but kept the tank)...I mounted the 12 gal. tank in the spare tire area, had a fill valve (schraeder valve) mounted to my bumper, and had a separate run from my compressor to my tank through a pneumatic switch... this way, I could quickly fill my tank using a large compressor either at home or from a commercial unit at a gas station (and I don't mean one of those little pansy ones that'll cost you $0.50), and flip the switch to 'top off' the tank using the ARB compressor or run it while I'm using the tank. The switch was used to basically allow the compressor to shut off and cool down in case I used all the air and didn't want the ARB to fill the tank back up. I also had an in cab guage to see how full the tank was. Never got around to setting it back up that way in the 4Runner...just lazy I guess.

just my $0.02

WET

 

[Mickldo]

Tyre pressure IMHO is one of the biggest factors affecting performance offroad. I've got two sets of tyres for my 80, 285/75R16 MTRs which I run at 36/38psi on the road and 18psi when I leave the bitumen, while my play tyres are 35/10.5R16 Simex Centipedes which I usually run at 12/14psi.
Regardless of what tyres you run reducing tyre pressures offroad will be the easiest ability enhancing mod to do.
BTW, do any mudders use or have heard of Staun Tyre Deflators? The easiest way to air down this side of CTIS.

 

[alvarorb]

OTOH, it may be overkill to do most of the trail with the rear locked unless it's a pretty serious trail. Today I did a bunch of steep dirt and loose shale/gravel hills and I did fine somewhere between 30 and 40 psi with the MT/Rs, FWIW. Only had to lock up once and that was cuz I didn't want to take a chance on sliding down the mountain... No snow, though...

Eric,

Not only overkill, but doing most of the trail with the rear locked could seriously damage your rear differential.
If you lower your pressure to 20 psi, you will have a larger footprint that gives you better traction. Plus the lower air pressure makes for a less bumpy ride. Don't worry about the tire coming off the bead. At 20 psi, is unlikely to happen.

If you get to seriously deep snow, you can air down to single digits, as in 8 psi.
Get your self a good air gauge that can read from 0 to 60 psi with good precision. I got a very nice analog one at Napa.

Regards

Alvaro

 

[Tentsontop]

Lockers

OK - lower pressure and easy on the lockers. Great advise. I learn something new everytime I visit mud.

Thanks again!

 

[CreeperSleeper]

A little late, but just so it's out there: I run 35lbs on the road (used to run 30, but this gives me a little better gas milage.) and 12lbs off road. However, I do not recommend doing this with 10" wide wheels like mine. With 8" wheels it will be fine, but I do have on-board air and I'm getting really good at resetting beads on the trail. If you don't have air, I would air down to around 16lbs.

 

[C6H12O6]

The major issue with low air pressures on the road isn't handling. Low pressures allow higher temperatures inside the tire because of the friction with the road and the motion of the rubber/belts inside the tires. Small trailer tires are consistently run near 100psi to help with temperature issues ~ smaller tires don't dissipate the heat as well and the higher pressures help make this a non-issue.

If anybody remembers the Ford Exploder issue with the Firestones, the real cause for all that (I'm paraphrasing a Firestone employee) was that the Exploders wouldn't pass the rollover test or accident avoidance test with higher tire pressures, so Ford specified the stock pressure to be lower, making the tire softer and a larger contact area with the ground. If people let the pressure drop too low below stock, higher temps caused separation of the tires. Bad juju.

Many of the mud or aggressive swamper style tires we run offroad are even more in danger of this when we run them at low pressures at speed on pavement. Either spend the $50 on a cheap compressor or don't air down if you have more than a SHORT drive on pavement. If you absolutely can't help it, keep the speeds down.