You definitely make some good points
Quote:
Originally Posted by Brad_SwiftFur
I've found my frame-to-ground clearance around 30" (rough guesstimate, air suspension inflated) but differential-to-ground clearance closer to 12". That will probably be the biggest off-road-ability factor.
|
You're right, differential and axle clearance are important (but don't necessarily limit you in practice if you choose smart lines), but equally or more important offroad are
approach, departure, and breakover angles. My concern with mounting a spare
below the frame is that it could substantially limit departure angle. But without having the bus in front of me or having more detailed measurements, I cant say how much of a limitation this would be. For a longer bus, an under frame spare probably wouldn't be an issue at all, for a shorter bus it might substantially limit it.
And yes, Ideally I would like to find a rear locking differential or limited slip. That + aggressive drive tires + a decent low gear, and some low tech self recovery gear and traction aids is about the best you can do without getting fancy and spending mucho $$
Quote:
Originally Posted by Brad_SwiftFur
And unless you have a locking differential, I wouldn't expect to do much off-roading with it. These things are *Heavy* and will sink on soft ground or sand (does this sound like the voice of personal experience taking? From the files of "Been There, Done That", feel free to ask me how I know!).
|
Heavy is a double edged sword. I haven't driven anything nearly as heavy as a fullsize bus, but I do have experience with a heavily loaded camper van, and in some situations that weight on the drive axle is helpful (generally speaking it improves traction) and in other cases it hurts (sand, mud, soft ground). A skoolie is definitely not the most sensible choice for an off pavement vehicle, but for light to moderate off pavement travel I think they can probably hold there own with a few sensible modifications if you can avoid soft ground. That said, I definitely am not speaking from a place of experience so I might be being overly optimistic. But I do know that there are many similarly heavy vehicles that perform well offroad with the right modifications.
Quote:
Originally Posted by Brad_SwiftFur
Also, I'm guessing the "overland" folks you refer to are driving smaller vehicles such as lifted 4x4's? Those 40" mudder tires are *Much* lighter than the 16-ply heavy duty tires our buses use.
|
I was referring to vehicles similar in size and weight to short to medium length skoolies (14k+ GVWR's). The 'expedition' overland vehicles are generally built for extended (or fulltime) self sufficient overland travel.
Unimogs,
MAN 4x4's,
4x4 Fuso cabovers, and
LMTV conversions are some examples. The medium duty vehicles often stick to ~37 inch tires on a 19.5 or even 16 inch wheel, but the heavy duty trucks use 20 or 22.5 inch wheels and beefier tires than even buses and semis.
Quote:
Originally Posted by Brad_SwiftFur
Also, we run much higher pressures and "airing down" the tires for off road use won't be as effective as, say, a set of Mickey Thompson's.
|
This is a very good point, and I think just an unavoidable factor of heavy GVWR vehicles. at the 11R22.5 tire size, its hard to find data or products specific to offroad performance. And it does seem like the ability to safely air down is questionable at best (I actually
started a thread about this on another site and got some good feedback).
Quote:
Originally Posted by Brad_SwiftFur
I'm sure you could rig up a rear-mount carrier with a lifting mechanism but at what point does it become a complicated solution for a simple problem?
|
Yeah, this is my thinking too, and why I was hoping I could mount it between the frame rails. Some of the $$$ expedition vehicles have very cool hydraulic rear rack systems that can easily raise and lower a
300lb tire and a motorcycle at the same time. But the added complexity and added cost of these systems is unappealing and quite possibly prohibitive.
On the other hand, I did see a pretty cool DIY skoolie rear deck build that used a small ATV winch and a pulley system to raise and lower the deck. The same general design could be applied to a tire mount.
But **** compared with roof raises, mounting VW's to the roof, and
whatever you call this a rear tire rack isn't so ambitious
I didn't set out to write a full length novel, but it appears I did.... seems to be a recurring problem for me..