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Hey all you Colorado guys,
There are two theories: If you want to cut down through deep snow to a firm base, narrow, high pressure tires work better, but if you want to float on top more, wide, low pressure tires work better.
In general, on hardpacked snow, the more "grabbing edges" the better, hence the GSA will usually work slightly better than the MT. You want the tire to flex a lot, to clean the tread and open up the siping so the edges can grab, plus you want the maximum amount of tread surface consistent with your speed. Since you should be going SLOW, you could try in the 25 lb range in town, and perhaps 35 on the highway.
On loose snow, or unplowed roads, the MT will work better at "digging" than the MT, which can tend to clog up. Again, more flex, more cleaning, just like on sand. I'd suggest the same as above.
More important than pressure is technique! Gentle, smooth acceleration using light BTM if necessary works well, but is usually unnecessary. If you are sliding around on acceleration, you are simply trying to drive too fast!
The MOST IMPORTANT lesson for snow is to know that your HUMMER, despite being a 4wd, WILL NOT STOP ANY FASTER! In fact, it will take a greater distance to stop than a small sedan. Remember ALL CARS HAVE 4 WHEEL BRAKES! Your stopping distance will be related to your gross weight and the amount of grab on your tires given the specific conditions, but will ALMOST ALWAYS be longer than a smaller, lighter car with decent snow tires.
The same is true for skids! You may have slightly greater traction due to weight and tire area, but it's largely offset by your greater weight, so you end up with only the smallest advantage in cornering and stopping, which should NOT be abused.
People tend to thing of HUMMERs as invicible traction machines....even me....I slid mine off our farm lane through a barbed-wire fence the first year I had it, leaving some nasty scratches in the hood, which I've left there to remind me that "slow and steady wins the race."
My winter driving is very tortise-like, nice and slow, very smooth, and I get my pleasure out of keeping going when everybody else is stuck or in the ditch. So, the jackrabbits may pass me, but I'll charge them $100 bucks to winch them out when they slide off up the road somewhere when I eventually catch up to them.
Oh, and CHAINS are a very good idea, even on a HUMMER, when things get very slippery....I have a set of 4.
I've been reading a lot of interesting posts regarding snow. Living in Montana we get about 6 months of snow (not this year - El Nino). About 5 years ago it snowed every month (19 months in a row). Living on top of a pass next to Bridger Bowl ski area, it's not uncommon to get snow falling by the foot. I love to off-road during the winter -- can't deal with cabin fever. The following is what I've found from snow veterans and personal experience:
Not all snow is created equal! Driving in fresh snow is different from driving in week-old fallen snow, drift snow, spring snow, hard pack, lightly fallen (2 inches) over hard pack, crusty, wet , etc., etc..
If it were a perfect world we could change tires at a push of a button. I have used MTs, GSAs, and Swampers and all have their pros and cons. Do not deflate your tires! Driving in mud and sand is different than snow. You cannot 'float' in snow with a 3 ton vehicle. My snow shoes have more surface area than a deflated hummer tire (contact area on a hard surface) and I still sink a little. You will also lose valuable clearance.
The SWAMPERS (38 x 12.50 x 16.5) I've found to be the best in off-road-snow driving. The lugs act as paddles and don't pack like the MTs or the GSAs. If your tires pack (fill w/snow) you might as well have bald tires. That's where chains come into play. I've never had to put them on the Swampers, but I have had to put them on the MTs and GSAs. Swampers are narrower (less surface to push against) and taller (more clearance) than the Goodyears -- a bonus. If you leave your Swampers on all winter, get them siped (center lugs). They will work better on ice. Boy, do they skate. Take them off for summer use if you have them siped, because dirt roads or off-roading will chew up your siping.
MTs are a good all-around tire, but they won't get you as far as the Swampers. In a 95 gas with Swampers, I had to go around a Hummer (96 TD) with MT's and break trail because it couldn't. The MTs favorite is hard pack with a couple of inches of fresh snow. They just eat it up! I run MTs on our XLC2.
Don't take GSAs off-road in the snow! If you do, bring a tissue! GSAs work the best on ice, hardpack or lightly fallen snow, though I have broken through some good snowdrifts. If they're long, you can feel the momentum drop quickly and more tire spin. I've tried various pressures, and the best I've found has been around 43 to 46 psi (warm). The grooves also pack very quickly when it's very cold out.
If you live in the snow and use the Hummer to drive around (no hardcore winter off-roading), go with the MTs.
The one constant I've found is that the wagons do better. The extra weight in the back helps balance out the front giving more even pressure to all wheels. It also provides more weight to achieve better contact with hard ground below the snow.
Example: I had to take a dead cow across the field during winter. Driving (XLC2) to the destination was no problem, returning was. Even though we were using the tracks we had already made, we went nowhere. The weight in the back was gone. We ended up having to use chains, and it still wasn't as smooth as the ride coming in.
Off-road winter driving tips:
The above is conditional on weather, conditions, speed and experience. Always drive SLOWLY. You may get there 10 minutes later, but you'll get there.
Finally, I've seen many posts about going through deep (3-4 feet) snow. This is very dangerous, because of the speed you need to accomplish this, and the resulting amount of snow flying against the windshield. I have problems with two feet. The deepest I've gone through is 41" and that was going down hill and not very far. Four feet is about 4 inches above the highest part of your brushguard. Personally I find it hard to believe people have driven through snow that deep, unless braking through short snowdrifts.
Gauging snow depth is very difficult. That's why I carry a tape measure in the car to check once I've gone through. One guy told me he went through 3 1/2 feet. Well, we measured.....26 inches. Remember you can't count the snow pack under your tire track.
If I can shed some light on to winter driving experience. Up here in Eastern Canada we get our share of everything. Light snow, heavy snow, sleet, slush, and best of all - FREEZING RAIN!!!! I have been drivng HUMMERs for 4 years now and the first time I drove across a drift on the road is not something I'll forget. The truck suddenly went squirrely. Some investigation found that this has to do with the fact that the HUMMER's alignment is set to full GVW specs at the factory. If you have the alignment readjusted to the "light load" adjustment, your Hummer dealer has the service bulletin that outlines the changes, it settles the rear end down immensely. And by the way, for driving on plowed winter roads, I'll take a GSA inflated to 35psi any day of the week. And if you have the detroit locker it's even better. But nothing aside from chains will help during a freezing rain storm. It is truly a white-knuckle experience to have little or no control of a 6800lb vehicle.
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