Discovery and inclines

In theory until CoG is outside the slope base :-))

I'd have thought with a Discovery/Defender you'd be thundering all the way down to the bottom all wheels locked before you'd go end-over-end.. I've seen videos of Unimogs doing a forward roll.

Probably the bigger danger, and one that's almost happened to me, is that when going down a slope the rear can overtake the front and suddenly you're sideways on the slope at which point you're in the shit! Clutch down and hang on basically.. That would probably happen more to a lightly-loaded 110 than a discovery due to the lack of weight in the rear, not so sure about 110 Counties.

Down: Vertical, or did you want the vechical to survive undamaged?

Up: Highly dependant on the surface and the tyres. I doubt my DII on well worn road tyres would do very well on a wet grass up slope but change the tyres to something more agressive or the surface to dry tarmac it do a lot better.

On or around Sat, 2 Jun 2007 09:25:49 +0100, "d-w" enlightened us thusly:

The disco is capable of a lot more than most people dare to do. The limiting factor is almost always grip. In straight up-and-down (no cross-slope) you could tip it to some fairly unbelievable angles before it'd go end-over-end - contemplate that the centre of gravity is probably not that far above the height of the top of the wheels and a bit forward of centre unless you've got a lot of weight in the back.

With a light-laden motor on some hypothetical ultra-sticky surface you've got to get the CoG outside the wheel contact points. If you consider a picture of the motor, that's going to take a really extreme slope.

That's the theory. In the real world, as mentioned, what usually happens is that the grip fails. If you're braking (including engine braking) then going down steep slopes the rear wheels will go light and lose grip. If you once get both rear wheels sliding, then a well-known laws of physics will make it go left or right and as Ian pointed out, you're very much into brown-trouser territory. The only cure for that is to speed up... which can lead to some exciting results. On the right terrain you'd get away with it, but you need a flat at the bottom to slow down on...

Uphill is even worse. Typical scenario is that you fail a climb and have to reverse down, and if you lack grip to back down under control, you have to do a fast descent in reverse and resist the temptation to brake as that loses you your steering control.

90 is shorter but lighter-bodied, at least unladen, so probably about the same. 110 gains a bit from the long wheelbase but a 110 truck can be light at the back unless you have suitable ballast.

Land Rover reckon pre-Td5 Defenders and Discoveries are good for 45' in any direction in terms of not breakng things or tipping over.

What one can *actually* achieve is dependent on a lot of factors, notably ground conditions, drivers determination and drivers skill.

It's nothing unusual for decent RTV sections to have short near vertical drops and finish with impossible up slopes, and CCV trials often take those to extremes.

I've seen a (new!) 300tdi Discovery I "jump up" (for want of a better description) up a 10 foot near verical rock face at Biggin Quarry (he would almost certainly have flipped over backwards if he'd failed), and I've been down that same one in a Series III 88in which involved the wor "plummet". Also in Biggin Quarry I've seen/driven various motors up and down slopes well past 45' - but only in the dry - when it's raining moving at all can be a challenge there! I also had my 101 teetering on going end over end (back wheels about 4ft off the ground I'm told - I had my eyes shut ) down an innocent 45' slope - definately Brown Caudroy territory....

At the end of the day, it's not really possible to say what's the steepest, as so many factors come into play. Similarly, it's not really possible to say a Defender would be easier than a Discovery, as external factors easily outweigh any vehicle constraints when taking things to the extreme.

Richard

Thanks for the responses

For info, I live in the Mendips and do most of my offroad on steep grass farmland whilst shooting.

Discovery is a G reg V8 with two LPG tanks under the chassis and all terrain tyres.

So picking up on the points raised:

The tyres are not exterme but not road either

COG: the LPG tanks should lower that a bit (depending on how full I guess) and the again I guess the engine block on the V8 might shift the centre compared with non alluminium one?

Crossing rather than vertical up/down: I try to avoid crossing (for all the known reasons) but there aren't to many flat bits around here so often you have to abd yes thats when it begins to feel hairy!

The terrain itself: how comfortable I am (or not as the case may be) largely depends on the length of the grass and whether its wet or dry - in fact this is what prompted the posting, as I was out several times last weekend both before and after it rained and over graised grass and sileage and was musng on how different things felt and trying to decide how far I could push things without comming to grief. Didn't come to any conclusion (nor sticky end) hence the post.

Keeping the car whole - it aint worth much but I'd prefer to to bend it too much :-)

On or around Sat, 02 Jun 2007 11:18:17 +0000, beamendsltd enlightened us thusly:

I gather you can get one to do that if the track rod lets go at speed.

I have had mine ate some serious angles, if it tipples over, it's too much.

When I did the Landrover course in a Disco at Solihull about 12 years ago they made us drive down the man made hill overlooking the plant. I seem to recall just about 50 degrees. First gear low ratio then as the vehicle begins to lose it, pour on the power gently thus keeping it straight. Under NO circumstances touch the brakes no matter what happens. When you hit the flat at the bottom EVERYTHING bottoms out and you hit the brakes hard.

With regards to crossing in slopes sideways, we were taught that if you can pickup an all old fashioned glass milk bottle from a wound down window you are at the limit!

Cheers Geoff

Thanks Geoff,

Like the last bit :-)

Don't think I'm close to that - maybe I'd better get a bottle though and see: getting a milk bottle these days may be the hard bit!

People Hi,

in line with Geoff's experience I can attest that a 50 degrees descent angle can be tackled with safety on a Camel Trophy Discovery 200Tdi. In fact it may be even more since I am sure that on occasions the angle was even more than that.

Tyres used were the Michelin XCL and XZL at 7.00 X 16 size.

Engine braking and a bit of careful use of the accelerator pedal when the tail is ready to slide towards the front is all you need. In any case the human ear's labyrinth (the center of evaluation of inclines and gravity) rings HUGE bells of alert way before the incline becomes dangerous for a vehicle. It is then up to the driver to fight his instict of survival and trust that the car will not roll or topple over. Most of all it is a matter of center of gravity, proper lines of direction and loading of the car. The rule of thumb though is to try and avoid steep inclines and especially those that require the vehicle to tackle them sideways. And when the stability is ready to be lost we always accelerate and steer the wheels towards the downside.

Speaking about CT vehicles, those cars are actually less capable for sideways leaning when compared to a civvy specs Disco. This is due to the increased weight on the roof and upper part of the bodyshell because of the rollcage. This is why the CT had a good fame of having at least a pair of rolled vehicles on each event.

Of course similar things apply for expedition prepared vehicles with heavy roofracks or three tonnes of equipment fitted inside them.

One more thing that has to be considered is the fitment of increased suspension height kits (the widespread +2" suspension lift kits). Those kits seriously increase the height of the center of gravity of the vehicle and this has a negative effect on the stability of the vehicle when the ground gets steep or inclined (apart from having a similar negative effect on the on the road handling characteristics and the way the car reacts to side-winds)

---------------

In any case though the Discovery (series 1 mainly) is a very capable offroader for dealing with steep inclines due to the relatively low center of gravity especially when someone considers the increased overall height of the roofline and the available headspace inside the car. The aluminum made external bodyshell panels do have some advantages after all.

Take care Pantelis