Can you eloborate on this one?

Are you saying that a wider tire will require less pressure for a snow run? Say15 psi on a 13.5" wide tire vs. 18 or 20 psi for a 12.5" wide tire (thinking 35's here...)?

 

You don't always want to dig down as that's when you start dragging stuff. If you drag you start to get in trouble.

I have done quite a few snow trail runs and once you dig down you are done. A large foot print makes a big difference. Also as you shear the top of the snow you get traction.

But once you are done your are done then its time to winch or dig.

 

I'm not talking about digging down with the rig (which is when you start dragging on stuff), I'm talking about digging down with the tire into the frozen ground below. The same principal applies with muddin. For short bursts across deep mud, you want to float on the top till you can regain traction on the other side. But if there is no end in site, you'll spin and eventually loose momentum in mud or deep snow unless you can get traction on good surface below. The only time that won't work with snow is if the ground under the snow is worse than the snow its self (ice).
I spend about 5 months a year "snow wheelin" in Maine. I don't know it all, but I've learned a thing or two over the years.

 

Nearly every time I go play in the snow I run into this same situation - someone is stuck because they didn't air down.
Me, I air down as soon as I get to the snowline. A good starting point is 10 psi. I've been as low as 6 psi with the stock Rubi tires but that was too low (great traction but drug the belly).
Remember snow is not like sand. Snow needs LOWER air pressure than sand.
The next lesson is DON'T spin the tires. The softer the snow the slower you need to go.
Be the way, my first investment was an air compressor. The Jeep drives for pooh after airing down low enough for snow.
My two cents.

 

I was out wheeling in the snow this weekend. We had a medium sized (eight) and diverse group. Three JK's, a YJ, an XJ, a ZJ, a Pathfinder and an Xterra.

Yeah, I know...we were feeling sorry for the Nissan drivers and decided to let them come along.

We had some experienced wheelers, and some complete novices. We had some nicely built rigs (the YJ in particular) and some bone stock rigs (the Xterra and the XJ).

Two things stuck out in my mind from that trip:

#1. The JK's (all three were Rubicons) spent a lot of time pulling the less capable vehicles out of spots where they were stuck.

#2. The less capable vehicles got stuck a LOT less once they aired down.


I recently got my hands (finally) on a compressor that I can use to air myself back up within a reasonable period of time. This meant that I had no problem airing down to 11 psi, knowing that I could air back up at the trailhead instead of running all the way back to town (30-40 miles) on aired down tires. Previously, I've aired down to 15 or 20 psi - dependent on how far of a drive I had back to a gas station with air.

All I can say is WOW. At 11 psi, it was almost as if there wasn't any snow. I was floating over the areas where smaller rigs were getting bogged down, and crawling (with no wheel spin) up hills that they had to take long runs at.

Yes, the fac that I run siped M/T's helped...but that low tire pressure wa a revelation. Knowing the theory is one thing, but experiencing the difference is another.

 

PSI and contact patch are of course related, but, generally, a fatter tire does better than a pizza cutter tire in snow.

That said, "snow" can mean a lot of different things.

Out by me, most of the areas I'm off road there may be some rocks, with or without a sheet of ice over them, or some frozen soil in the same condition, under the snow, and, the snow may be crunchy and hard with some texture, or, a glazed pack, or powder, and so forth.

Sinking down through the "snow" to a sheet of ice does not add much traction, in fact, ANY sinking down is typically presenting the leading edge of the tire with a taller ramp to climb in order to move.

In a low traction coefficient condition, ANY added resistance can kill your ability to maneuver.

Lowering the pressure makes the contact patch wider, but, also, LONGER.

A LONGER patch helps forward motion immensely (Think tank tread).

As for the tread....well, the contact pressure your rig exerts on the tread block is what sinks it into the terrain to gain traction...or not.

Just like soccer cleats bite well in turf, but suck on a basketball court...MT's tread blades can do really well if the snow is soft enough to paddle, and horrible if packed too hard to sink a blade into.

AT's actually do better in harder packed snow than MT's, especially if they are heavily siped, etc.

I was winter wheeling a few times with a set of new LTB's.. I used my siping gun to help them cope with the known icy conditions......and it made a huge difference.

Airing down off road is always going to help (Chain exception is a good one)

HOW MUCH to air down is specific to your rig, and to the tire itself...they have different load ranges and characteristics.

 

Well said, Teej.

 

My brother was on vacation last week. Monday afternoon, we decided to take our Wranglers out for a run after 16 inches of fresh snow fell. We headed for some county fire roads out in the pine barrens. Most of the trails were virgin, with a couple showing snowmobile tracks.

I left my 32" winter Goodyears at 32 psi, my brother aired down his TJ to 15 psi. I broke the trail. I kept my speed up around 15 mph. After about 30 minutes, we traded positions. The first thing I noticed was the TJ was not getting as good of a bite and his lesser ground clearance was not helping. Especially where the snow drifted. After about 15 minutes, my brother waved me past.

We covered just under 14 miles. I never came close to getting stuck, not even when blasting 30" drifts. The TJ did alright, but the JK was simply better.

Under the snow conditions we had (very cold, blowing snow) I saw no advantage in airing down. The snow was light and fluffy, easy to blast through. The ground underneath was mostly packed sand, and if I spun the wheels a bit, the tires would dig down and throw sand onto following TJ.

I wanted to try that ride again when the snow was damp and packing, but nature intervened with two days of high 60s temperatures.

As we drove out of the woods, we spotted a Deputy parked at the entrance to the fire road. He waved me over. I rolled down the window.

"You didn't happen to see a couple of quads up there?"

"No, I saw some evidence of snowmobiles though."

"You know, you're not supposed to be on those trails either. These are county fire access roads."

"Something tells me that there won't be any wild fires today."

The Deputy gives me a look, just as my brother pulls up in his TJ....

He looks at the TJ with amusement on his face. "Hey John," says the Deputy. "I didn't recognize your Jeep."

"Stop annoying my brother", says John with a grin.

Yeah, my brother is also a Deputy.

We talked for a while. My brother gave the Deputy his thermos of coffee and we left him to his quad watch. We headed to town to get a beer and some steak fries.


My regards,

Widewing

 

Great quote, good story.

 

Yep, as I said before, airing down isn't always the best solution for driving in snow. It's like a mud puddle... you need to know what kind of snow it is, how deep the snow is, and what's underneath it. Life lessons learned wheelin in Maine!