unibody vs truck on frame design

[StumpyPete]

Originally Posted by rh71

I've been following this thread to see if anyone would mention it but nobody has - what about actual off-roading? My Rodeo is on a truck-frame and while the comfort and ride suffers (only in comparison), it has one of the best 4WD systems for its time and is a great off-roader (think rock-climbing). I know nobody buys our $50k+ vehicles to go off-road but then there's this question about unibody vehicles [at any price] being the superior design for an SUV... truck frames = better off-roaders, no? Embarrassingly, an infamous review showed the X3 couldn't climb a small hill on dirt.

What about current Range Rover - isn't it unibody - it can go anywhere!

[jimsaq]

same again - it's the suspension which is more important than the chassis, generally speaking. the typical wishbone IFS setup you'll find on most recent 'offroaders' doesn't lend itself to downward travel very well compared to beam/live axle. traction control or difflocks help a lot, but it's still better to have as many wheels on the ground as possible in terms of distributing the torque across as much contact patch as possible

what vehicle is a rodeo in the US? in australia it was a small japanese-style pickup put out by holden. not really great off road due to independent front suspension and a rather lame LSD in the rear

[JCL]

Originally Posted by jimsaq

what vehicle is a rodeo in the US? in australia it was a small japanese-style pickup put out by holden.

You probably know it as a Frontera.

[jimsaq]

it can go anywhere*

*actually not very far once the going gets tough

[Fraser]

Originally Posted by jimsaq

*actually not very far once the going gets tough

Current Range Rover, actually designed and developed when Land Rover was owned by BMW, is brilliant off road as long as it is optioned with the rear self-proportioning/self-locking 'electronic' diff. Standard spec is a centre 'e-diff' taking care of inter-axle control while electronic traction control takes care of cross-axle control at both ends. As such the RR is okay but not brilliant off road. But add the rear locker (a $2000 option here in Australia) and it completely transforms the vehicle. I drove one just a month ago off-road and it's about as good as it gets. The Range Rover's height-adjustable suspension is a big plus off road.

[jimsaq]

hehe
that's where it gets subjective I guess. I've driven them too several times over the course of the past 3 years, they're a nicely kitted out vehicle for one straight off the factory floor but they are such a long shot from 'as good as it gets' it's not funny

what isn't subjective, is that the current range rover with height adjustable suspension and rear locker can't get up say, ormeau's tower of terror because it doesn't have the underbody clearance or suspension travel required. and the tower of terror is at the easy end of 'going gets tough'.

[Fraser]

Originally Posted by jimsaq

hehe
that's where it gets subjective I guess. I've driven them too several times over the course of the past 3 years, they're a nicely kitted out vehicle for one straight off the factory floor but they are such a long shot from 'as good as it gets' it's not funny

what isn't subjective, is that the current range rover with height adjustable suspension and rear locker can't get up say, ormeau's tower of terror because it doesn't have the underbody clearance or suspension travel required. and the tower of terror is at the easy end of 'going gets tough'.

When I say "as good as it gets" I'm talking about showroom stock 4WDs. Not modified stuff. As far as showroom stock, tell me something that's a lot better?

[FSETH]

This has gotten a little off topic.

bnz2bimmer, are you interested in serious off-roading? Is that why you like a body on frame design, or do you mainly drive to work and to the stores on paved (gravel at worst) roads like 95% of X5 owners? If you drive your X in conditions that the typical X5 owners does, I am not sure what you feel the benifit of body on frame design is.

[Fraser]

Yep, sorry, well off topic.

Getting back to monocoque vs body-on-frame, aside from Land Rover with its Discovery 3 and Range Rover Sport, no-one has really put much development money into body-on-frame tech in recent years. And LR paid the price in weight trying to achieve a best of both worlds result, ie., monocoque stiffness with separate-chassis practicality. All the recent big-money development has been with monocoque and that's where things are going and have been for quite a while.
There's no real off-road benefit in terms of capability with separate chassis designs although they offer protection of vitals and general robustness. It's also somewhere to hang frontal protection, long range fuel tanks etc.