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-   -   Monocoque SUVs : Advantages and Disadvantages (https://www.team-bhp.com/forum/technical-stuff/129446-monocoque-suvs-advantages-disadvantages-2.html)

Land Rover began building the Discovery on a monocoque platform some time in the middle of the previous decade. The Discovery is a good off-road SUV apparently.

Unless we're talking heavy-duty vehicles like light-trucks for commercial purposes, I believe monocoque-construction is the way forward.

I'd learned recently that the Suzuki Grand Vitara is built on a unique blend of ladder-frame + monocoque construction. Possibly to extract the best out of the vehicle under most conditions? Samurai will have great insights on this one. :)

I guess this is a nice thread to clarify one doubt i have been having from some time now regarding monocoque and body-on-frame SUVs.

Basically it all started with GTO's thread on whether to go for a sedan or SUV and many have opined that one of the biggest advantage of going in for an SUV than a sedan in that they are stronger than sedans and hence can handle bad roads better, especially for people like me living in coastal areas where every monsoon is followed by deterioration of road conditions!

My query is that are monocoques or body-on-frame SUVs better when it comes to this aspect. In other words if one prefers to choose an SUV over a sedan because he drives mostly on poor roads and needs a stronger vehicle will it make sense to go for a monocoque (which is essentially built on a sedan platform with light construction) or to go for a proper old school SUV?

I am very reluctant to shift to an SUV because i do not want to lose on the driving pleasure sedans give but if i have to due to the bad roads, then will it be better to go for a body-on-frame SUV?

Wonder why Monocoque SUV's are needed in the first place. Only for the image (which banks on general misperception of capability associated with looks) and high seating position?

How different are they from Stationwagon/Estate cars, which actually blend in the driving pleasure of a sedan with practicality (and in some cases three row seating configuration).

To some people, Monocoque SUV's are nothing but minivan's (commonly known as mommy-mobiles) on steroids.

If the Monocoque SUV's are built better to handle a weight of (around) 600 KGS excluding the weight of the car, the car performs very well for occasional off roading. If the manufacturer uses poor suspension, then it cannot be guarrenteed.

Ideally, These cars are called & categorized as SUV's. So the company tests it as per SUV standards. In most of the cases, this testing exceeds our real life usage. So these SUV's should be light on pocket + Simple to Drive. I feel it so.


Why not? There are some temples and some waterfalls in ooty, munnar, Srisailam, some tourist spots in kodai kanal where the roads are bad and the pot holes are big. i dont think sedans with 170 mm GC will make it without scrapping. Forget about these places, there are many people complaining of GC issues in their sedans, who drive in B2B bangalore traffic.

So i prefer to have a SUV, which could give me a sedan like FE and handling and has good GC. Yes, some sedans have 185mm GC (Linea) but that is one of its kind.

The answer lies in your post itself. Linea can make it. SX4 too is one example. My Ikon 1.6 has been through hell and back without bottomscraping. There were sedans in the past that had ground clearance to put modern crossover-suv's to shame.

Still waiting for the reply to this question that Carfreak had asked. I am eager to know what Team Bhpians have to say about this.

One reason in favor of old school SUVs which has not been quoted yet is the fact that they are not car like, they feel different to drive, may be little crude (I like this crudeness), more of truck like and probably, this is the reason some of us love them. I regard them as a true SUV with lot scope to work on them, improve them, mend them, modify them.

I bought a Bolero SLX (body on frame SUV) this year in January and drive it mostly on rough roads, showing no mercy to the poor Bolero. The advantage of owning this old school SUV is that it is true VFM product, no frills, has got almost nothing to break in case of minor bumps (read as collision) or bone jarring pot holes (we have plenty of them). Only minor scratches and dents is what I get in return of rough driving, which doesn't deteriorate its not so beautiful (crude) looks and also do not burn hole in my pocket when I go to get them fixed. Whereas the beautiful looking monocoque SUVs which just looks like a swollen hatch or sedan (no offense) to me are good on tarmac for urban use and are more of a style statement among city dwellers. For me buying monocoque SUV after a sedan is like buying yet another different looking sedan.
Go out and try something different:)

Just my two cents

Yes, it would make perfect sense to go for a monocoque. In fact, gone are the days when a chassis under the body was the only way of making a vehicle tough.
As a shining example, one of the most competent SUVs in the world, the Mitsubishi Montero (Pajero in most markets) is a monocoque and not a ladder frame vehicle.

SUVs were initially developed on ladder frames because they were derivatives of pick up trucks, which in turn were on ladder frames.

Monocoque chassis is the manufacturer's answer to high volume manufacturing at a lower cost. Unlike a Body on Chassis design, for monocoque you need a heavy investment in body dies, which makes sense in a high volume environment. So the capital cost is high, but unit cost is very low.

As far as SUV goes, it is the design and intended use and not manufacturing technique which designates the type of vehicle. A well designed monocoque chassis will be stronger, more rigid and cheaper to manufacture (provided numbers are there). Where it falters is in accidents where a any serious damage impacts safety and repairs are expensive, as structural integrity has to be maintained.

One advantage of Body on Chassis design is that for the same basic chassis, you can bolt on various bodies and change style at a relatively low cost. This was what American cars did before the monocoque chassis was introduced.

To sum it up -
. Body on Chassis design results in low initial cost but high unit cost. Cost of design changes to the body are low. The down side is heavier vehicle and less rigid structure.
. Monocoque body is a high capital, but low unit cost, hence ideally suited for large volume production. The body is more rigid and lower in weight compared to body on chassis. The downturn is high repair costs in case of accidents and high capital costs for every change in design.

Actually i have indirectly included another comparison here-between sedans and monocoques! Will a monocoque be more tough overall than a sedan which is built on the same platform?

The Montero may be an exception as it may have been designed from the beginning to be tough and rugged unlike the crop of monocoques entering our market which are essentially based on sedans.

This guy here puts in some interesting analogy between Body-On-Frame and Tiered Software Architecture, quite true to certain extent.

http://monocoque-software.blogspot.i...monocoque.html

Also a very good point-wise comparison here:

http://www.whyhighend.com/monocoque-...r-chassis.html

A monocoque is a monocoque, in whatever body form.

Its toughness is engineered depending on its intended application and some buffer.

The Montero, while being amongst the best, is not an exception.

Going slighty :OT with regard to Suv's- Most of the cars produced are designed keeping large volumes in mind. Hence monocoques make sense for the companies. That need not imply that body on chassis type are at a disadvantage. If fiberglass/aluminum body panels are used then weight can be reduced also accident repair will be easy- no denting, painting just replace the whole panel!. sports car maker TVR had used such body panels in some of their models and they handled real well, busting the rigidity myth.With the technology available today it would be a breeze to create and roll off various models using the same chassis structure with diff engine combos. It is just that there are very less small-budget companies which go for the inexpensive body on chassis construction that i believe is leading to the decline of this wonderful but sadly dated methodology :Frustrati.

True. Even Monocoques have been around for ages now.

But the question is, why sandwich a Monocoque and SUV looks. A high perched SUV is so, because it serves a purpose. A monocoque SUV simply intends to look like an SUV without needing to have much of the capabilities of a body on frame structure. In other words, why do you need it?

Now would a monocoque sedan/estate (with good ground clearance) be better than a monocoque SUV?

This is exactly my query! Does it make sense going for a monocoque SUV over a body-on-frame SUV? Is it not better to go in for the latter if one wants an SUV?

Hi,
That is an interesting discussion taking place on vehicle design of monocoque vs chasis mounted. But my concern is that some may arrive at conclusions from this discussions, which are not very true and may result in unsafe situations. A pure monocoque design is the one where all the forces acting upon a structure are borne by the skin of the structure. An egg is perfect monocoque structure.

It can therefore be seen that a monocoque design will certainly have lesser parts and can be assumed to be lighter and simpler as compared to another design for same amount of loading. However, ability to withstand the amount of load is limited in a monocoque structure. This aspect is now being catered by advancements in metallurgy, manufacturing processes and their availability at economical prices.

Issues of drivability, handling, strength, weight and all other desirable or undesirable features are a result of many other factors and cannot be attributed to constructional design alone. These are affected by number of independent and related aspects, one may obtain very similar operational parameters in either of the two discussed designs. Therefore would recommend that before arriving at any conclusions please take a holistic view and don't go by any one feature.

An example here is that of a military tank, perfect offroading machine, did away with chasis type of construction somewhere during WWII. Aeroplanes have been flying with monocoque/semi monocoque designs prior to WWII. But till date no heavy hauler has been made without a chasis and Hummers have chasis.

cheers