Thursday, Oct 10, 2002 at 00:00
Yoda,
These are good questions. I wish I had known more when I started looking for a 4WD.
Ground clearance is a function of more than one factor. First, there is the measure of the lowest point to the ground (say the diff, or the cross-member under the engine), which is what you are referring to. That particularly matters when you are on a track with a high centre, or deepish wheel ruts, especially if the vehicle has limited wheel travel. You can compare that measurement on different vehicle with a tape measure. If the Forester rates 200mm and the X-Trail 150mm, that is probably what they are measuring. Second (and perhaps as important) is ramp-over angle. If you go over a hump (like an erosion control mound, common on 4WD tracks) and your front wheels are on one side of the hump and the rear wheels on the other, will the belly of the car scrape (or worse, hang up) on the top of the mound? The better the ramp-over angle, the less chance of that happening. (Going over the mound at an angle can help too.) A car might have a good ramp-over angle, although the distance from the lowest point to the ground is not great. (My impression was that the X-Trail might have an advantage over the Forester in this regard, but I am prepared to defer to others on this, as I haven't driven the Forester off-road and everyone speaks well of it there.) Third, there are approach and departure angles. That means the angle at which you can enter a steep dip without scraping the front, or exit it without scraping the rear. Most of the time that is not a huge issue. Fourth, there is wheel travel. If you have to drive over a big rock, or drop a wheel into a hole, or drive in deep ruts, will the wheel have enough travel to remain in contact with the ground, keep the other wheels on the ground, and keep the body clear? This may be the most important of all, and it is where vehicles with live axles (e.g. Patrol) have it all over vehicles with independent
suspension (e.g. current Pajero, or any light duty 4WD). If you look at say a Patrol, the distance from the bottom of the diff to the ground is not that great, but the Patrol is one of the top vehicles off-road in part because of its excellent wheel travel. (Aust 4WD Monthly do a ramp test on vehicle to measure wheel travel, or articulation, but given their prejudice against light duty vehicles they probably haven't done these two.) You can modify a vehicle to change any of these things: for example, you could get bigger diameter tyres and a lift kit and aftermarket
suspension (e.g. Old Man
Emu if available for the vehicle), if you want to spend the money. But if you are thinking about doing all that, in order to do lots of tough tracks, maybe you would be better looking at a more heavy-duty 4WD in the first place. (Steve will say, "Crap, look at my Freelander" and I can't contradict that!) I agree with Steve about the All-Terrain (A/T) tyres, though. They are well worth the money as they add a lot to off-road traction, especially in muddy or rocky terrain, and are much less likely to cut on a rock or stake. They are a tad noisier than highway tyres, but not dramatically so. BF Goodrich and Cooper are, as Steve says, highly regarded. BFG are noted for extra strength sidewalls and therefore popular in mountain areas where there are lots of rocks (e.g.
Vic High Country). Check their web sites, or ask a tyre specialist, for details of whether the appropriate size is available for the vehicle you choose. Don't despair if they are not available in the appropriate size though - other brands are good too. We got Uniroyal Laredo ATs for our Vitara and they have been great. Also agree with Steve about bash plates. Light duty 4WDs generally don't have the same degree of underbody protection as the traditional sort, and if you ding, say, the transmission on a rock it could cost heaps. Bash plates are cheap insurance. Whichever vehicle you get, have fun!
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