Which is best: stiff or flexible chassis

No there will not be consensus. Particularly given that "stiffness" is an open book. There will be a group who say that a set of chassis rails and beam axles is the only way to go. Then there is the group who will say a monocoque, vis Pajero and others, IFS all round and great traction control systesm offers the same amount of capability. So they are the two opposite poles or camps I suspect

It also depends on what you mean by stiffness. If you are chasing maximum off-road traction then beam axles on coil springs gives you that and there are plenty of vehicles in that camp. LR Defender, Nissan Patrol etc all with chassis rails. But a well driven anything with either a monocoque or rear beam axle and IFS with our without a chassis rail will go a very long way off road as well.

From a purely engineering sense a high level of rigidity in a vehicle is not good. Overall any 4WD must have a degree of body flex or it will fall apart. This is accomplished by rubber engine mounts and chassis mounts etc

Regards

RobA

Stiff.
IMHO Its OK to have a flexible chassis, as long as everything around it flex's with it, take a ute for example, will the body flex like the chassis will?,what happens if the chassis "out flex's" the body?
The company I work for had quite a few problems with this on garbage trucks and was never fully resolved, new trucks are now spec with double chassis to make stiff so it doesn't crack body's, causing them to leak.
This may not fully relate to 4WD wagons, but I personally rather let the suspension bend, not the chassis.
Shane

Can you define rigid? Unimogs are designed to flex but I wonder if you’re talking more about monocoque Paj’s and the like.

Having been balanced on diagonally opposite wheels on many occasions, and done much snatch strapping over the years, and wanting to avoid cracked windscreens or a distorted chassis, a rigid chassis for me any day (assuming a ladder chassis Patrol qualifies as rigid by your definition).

Cheers

Depends on the rest of he vehicle and the suspension design.
The Unimog has flex chassis PLUS long travel suspension and is the best, but building a body on one is fraught with difficulties and constraints.
The Canter has a flex chassis and poor suspension travel.
The OKA has a very ridgid chassis and good suspension travel and off road performance between the other 2. It is the easiest to put a body on by far compared with the other 2.
Horses for courses......

Cheers,
(no bias) Peter
OKA196 Motorhome

Flexible for me Bandicoot.

AS represented by the 80 series and GQ patrol chassis of the nineties.

The cruiser had hard steel , and I was shown the cracks that developed on a mine unit around 1992 just before it was shipped back to japan.

Eye opening , and helped me go for the more flexible Patrol then.

I thought the chassis under my Jackaroo was too flexible as the bullbar shook around all over the place (relative to the car body) on rough roads, and it was too much for the IPF lights (despite the salesman telling me they'd be okay!). I've heard that chassis flex also makes fitting a bullbar difficult on the 120 Prados as well (you need to ensure adequate clearance so the bullbar doesn't hit the bodywork). The upside of a more flexible chassis is that it isolates the cabin from a lot of the road noise (the Jackaroo transmitted very little road noise into the cabin) and makes for a more comfortable ride - let's face it, that's what most buyers of 4WDs want these days whether they're towing a caravan or dropping the kids at soccer.

Personally, I think I'd like to have a stiffer chassis on my next car, but I'm not really sure how to find out what is stiff enough, and what isn't?!

Avoid the complete monocoque shell construction 4wd's then - no stiffness at all without the little blue pill! ;o)

Cheers

Ive never seen a rigid chassis on any 4wd. Sure ,some may have more rigidity than others,but they all flex.
Even some of the monocoques like the Pajero can flex a fair bit.