Things like mud and snow require the tires to spin relatively fast to aid in self cleaning and for mobility. Think of it as reaction traction. For every pound of goo you sling backwards, one pound of vehicle is pushed forwards. A higher (numerically lower) ratio like what is in the H2 would be better for this, but it will require more power because of the loss of mechanical advantage given by the lower ratios. The other choice, if you have limited power, is to have an engine that has a very high RPM range to counter the speed reduction of the gear sets. Often the best choice off road is to select the low range in the transfer case, and a higher gear in the transmission. As a general rule in vehicles equipped with manual transmissions and low range ratios around 2.73:1, low range and 2nd or 3d gear is the approximate equivalent of high range and 1st gear. Automatics are geared different, so the rule of thumb is harder to apply, but 3d gear/low range seems to match close to 1st gear/hi range. Obviously with a manual in low range, you have better gearing selections, both faster and slower then if the transfer case was left in high. Over all, it comes down to the type of wheeling you do most. If you are a mud bug, you want huge power and higher gears. If you are a rock crawler, you want light power and low gears. If you are somwhere in between, like most people seem to be, something in the middle will work the best, but not be the best for the extreme ends.

 

hmmm... reaction-traction. i guess you'd have to toss quite a bit of mud to move an H2. []

That was an interesting read, cool. How about for powering up steep hills? Does anybody get their jollies out of that? Outside of a big run at the hill, it seemed in my toying about that the H2 had a good combo for that.

I suppose low-gearing could drive an H3 or Wrangler up any hill, maybe just slower? What the heck is the limiting factor for hill climbing, anyway? Traction of course, but is the traction tire-based or does it come down to locked diffs and computer traction control and all of that? Center of gravity would play a role, i guess, ultimately limiting how steep you could go w/o tipping, or w/o mild tipping that lifts the front a bit? dang that would be steep. so its probably traction/power.


I think i'm getting a rough feel for how all of these different things - jeeps and hummers and differentials and wide and heavy and light - sort of interact. And i accept that its not raely possible to say "better" or "worse" except in obvious cases. A skinny little jeep can sneak through some narrow trail amongst the trees. A big wide hummer can rip down an open trail at far higher speeds & is less likely to do this: http://www.vintageoffroad.com/videos/hellsroll2.mpeg (watch til the end).

on a side note, an H2 breaks a tie rod when its tire slips off a rock and the truck lands with tie-rod-on-rock... and it finds its way to what? 100 places on the web?

some guy does that and nobody cares. you do have to admire the ability of the hummers to draw a crowd - real or figurative cyber

 

You are getting the idea. For hills, the big thing is tipping over. If you have a low center of gravity, then it becomes more of a traction thing. The climbing numbers for the Hummers are for a vehicle properly loaded to max GVW in high range, and probably represents the steepest incline that you can maintain traction to climb, or the safest sideslope you can cross without rolling over. Somwhere amonst all of my junk I have the formulas to figure out where your center of gravity is on your vehicle for any loading configuration. Once you do that, it just becomes a matter of determining the maximum angle to keep the center of gravity within the wheelbase/track and you will know how steep of an angle you can climb/cross without rolling. Then all you have to do is worry about the traction aspect of it, and that can change from one day to the next, or from one run to the next.

 

that's interesting about the gross vehicle weight in high range. hi-open? that's very interesting. because the H2 can scale a steeper slope than its rating. i would suspect that for safeties sake the vehicles are rated quite conservatively.

a formula for calculating center of grav would be interesting. very interesting, i think i'll google for a spec on the H2 with respect to that - center of grav.

 

hey linus, i think the FJ Cruiser is another vehicle with over-stated clearance. almost 10" is the spec... but by my measure today its not as good as the hummers.

i'll zip over to the lot and take some pics as i did with the wrangler.