Suspension flex verses offroad stability.

[daddylonglegs]

For ages now I have been intending to do a series of tests to determin if a L/Rover/RangeRover with a super flexy suspension is more likely to overturn in crosscountry situations when compared to the more standard versions. One test was to drive the truck up an articulation ramp with difflocks engaged to find out what point it loses stability. Then I would back down, strap and block the suspension and drive up again to see if it was either more or less stable. The other test would be to place the wheels on one side on a platform attached to the lift forks of a forklift.,
raise it untill we reach the stability limit and again try it with the suspension strapped and blocked.The vehicle would have a safety chain on each test to prevent it falling over completely
I was wondering if anyone has tried this before, and if yes, what were the results and conclusions drawn?
Bill.

[skids]

Yes bill a thousand times yes if a wheel falls into a rut long travel suspension will not drag the body down with it but simply allow the body
to remain more level than if it had standard suspension.
I have experimented with my own articulation kit in this situation and it
is alot safer. just ask mum

[ISUZUROVER]

On trips it has always been the vehicles with stock suspension that seem to have rolled (this has been mostly leaf-sprung vehicles). Sure there is a driver error factor involved (and the drivers were usually less experienced), but vehicles with longer travel seem to be able to drive over the same terrain without problems.

[landy_man]

if a wheel falls into a rut long travel suspension will not drag the body down with it but simply allow the body
to remain more level than if it had standard suspension.

i dont think the weight of a wheel and tyre is going to drag the whole body of a car over..the wheel would simply hang there...

Bill... I think once you add lockers to the equation things get messy because you still have drive at the wheel that is on the ground and keep driving, this in my opinion is when people start rolling their rigs

[Gwagensteve]

sorry for highjacking a rover forum but this is a really interesting topic. I think there is another issue, and that is if the car can settle onto its bumpstops. Many of the "custom" cars built suffer from coil dropout or scissor shackles etc AND are unable to settle onto their bumpstops due to overly long springs/ SPOA conversions with inadequte bumpstops etc. I have found that if a car is not "settling" it will not be stable.

We experimented with Bigsteve's sierra with unbolting shocks etc to get it to "settle" and the stability increased heaps when it coupld settle onto its bumpstops.

Generally, I tend to like to see a car that will compress fully onto its bumpstops and has retained springs, as I reckon that when a car has unretained springs, it will be harder to get the compressed wheels to really load up and settle onto the bumpstops. If this is the case, the car will a) be sitting higher than neccessary, and B) will be able to wobble around a bit as power is applied etc.

I would rather trade off a bit of travel (especially if it is via unretained springs) to get a car to "settle" when getting close to falling over.

sorry if this is a bit confusing, and it is a bit of a mishmash of ideas from the spring length v wheel travel thread too.

[hotrod4x4]

i totally agree with a reasonable amount of flex making a better trail rig.....it does in most cases make it alot more stable

but theres DEF a point
if u go too much flex......u lose the stability

same as a truck with coils
if their tied in .....the trucks alot more stable than if not tied in

[landy_man]

check out this discussion on retained springs half way down the page...

http://www.pirate4x4.com/forum/showthre ... ng+springs

[skids]

If the lbs of the springs is correct and matched to the aplication when compressed it will offer enough resistance to compensate for the extra
weight loaded upon it when compressed.
landyman go back one of your wheels into a large hole on a incline tell me
didit it lift the front wheel pretty high,it will unless you can allow the weight of the front of the truck to hold it down ,the rear corner weight
of the truck will be holding it down into the hole, how ever if i reached under and poped that shock off it will allow the weight to shift back towards the front and help level out the ride position and that weight difference can be as little as the weight of the one wheel and axle,brake assembly,if you can release that weight it will help with stability .

[daddylonglegs]

I have to agree with Ben. Every Landy I have rolled, and there has been quite a few, have been on standard non flexy suspensions. I have done much more extreme things with my current setup with dropaways front and rear without yet coming to grief. It has felt a bit dodgy on occasion, but when I pushed my luck and pressed on it came out ok.
I think on the Ramp test that I suggested at the beginning of this thread, the non flexy rig would overturn much earlier than the flexy one, but on a side slope I am not sure. It may all depend on the roll geometry of the suspension linkage. According to my Pommy book on new directions in suspension design, it is entirely possible to build a suspension that is soft and compliant, and still have excellant stability.
Anyone have a forklift or a 4 post hoist in melbourne ?
Bill.

[aliread]

This is a topic that can and has (in the UK forums) gone on for ages. As to weither which is better, lots of travel or a bit more than standard
Personally i have gone the bit more than standard. Main reason is that the wheel will hang in to holes a bit more than stock and keep the body lvel and stable. But the extreme travle trucks may look great on rocks and stuff but on side slopes there are very scary. The whole truck moves to tip the body off the chassis becuse the springs will not hold the top side down.
But if you have Lockers which most of us have do you need huge amounts opf travel to get the tyre on the ground. After all a truck with massive travel looks good but what weight is on the tyre on thr ground to add in the traction . The answer is sod all . So you have to use the locker, so it might as well be in the air

[daddylonglegs]

Most people including your good self, disregard the contribution the seesaw action of the axle makes once a spring has reached its extension limit. They see the dislocated spring and assume the wheel on that corner doesn't have any weight on it. But I do agree that most long travel set ups can be scary. What is needed is a suspension linkage that places the roll axis/ centre at the same height or slightly above the centre of gravity.
Then the way I see it, no matter how much the chassis rolls on its suspension on side slopes, the rollover angle would remain fairly constant.
I am all doped up with painkillers at the moment so I could be talking a load of crap.
Bill.l

[BIG RANGIE]

i run big lift , spring and body and 4wd with friends who have modified and stock 4wds, when it comes to ruff or uneven ground on the flat or up or down hill my articulation lets me walk over stuff that gets atleast one wheel in the air on a stocker, on the flat this is not a big problem but up or down hill can become dangerous, i think the amount of lift and articulation is a decision based on what you do with your 4wd. I only drive on road to go 4wding so offroad is most of my driving. as for side slopes you must be careful in any 4wd and more so in one with big lift .

ps. i have a coil sprung 82 rangie with big lift and big wheels, i havent rolled her over yet but i try to stay well away from big side slopes.

[Aquarangie]

My attitude to springs are keep them soft. hard springs are no place on a Rangie, unless you tow a lot or do lots of outback travelling.

I have softish springs I got off a mate when we upgraded his suspension (origin unknown), but they give great flex and with the RS9000 Ranchos and the length of travel oat the rear they work well. I usedfto run Kings all round but gave them the flick after a few months as I had wheels lifting up all over the joint and the lack of compliance in the springs made my articulation worse (it felt they way!!)

When I run out of travel, thats where diff locks come in handy (maxi rear, air locker front).

Regards,

Trav