Another Live Axles vss Independant Suspension Thread

[Fluffy]

Hi All,

I know this has been debated before.

I still cant understand why live/solid axles are so superior to independant suspension.

I am no mechanical genius, nor am I a complete ignoramous. (spelling)

The way I see it live axles leave the pumpkins and shafts exposed. Independant suspension hides and protects diffs, transfer boxes, prop shafts and drive shafts from damage.

Sure, if you are looking at HUGE lifts/articulation that would be difficult on independant suspension then solids have an advantage.

But in the normal overland/trail world, not competition Level 5 stuff, where we also travel at high speeds on tar, surely independant is a better compromise.

I have two Range Rovers, one with solid live axles and one with full (IS) independant suspension.

On the live axle one I spend my life in fear of smashing my pumpkins, wacking my transfer case or knocking a propshaft. Been on trails where we have aborted and returned home because of this. (Not me, others with me)

On the independant suspension one, my biggest fear is putting a dent in the exhaust. On trails I have never seen an IS damage anything that aborts the trip.

Good scientific answers would be nice.

Cheers
Keith

[ThysleRoux]

Keith, I'm no scientist, nor an engineer, but regard myself as fairly logical.
IFS is designed to reduce the unsprung weight ( the components not supported by the springs/shocks) of the vehicle, thereby enhancing on-road handling. Because of this, the components are generally of a lighter construction and thus not as robust. Here I'm talking about things like control arms, drive shafts, etc. The springs and shocks will also be designed to be "weaker" as they do not have to control the movement of the heavy components associated with a live axle. The only components on a live axle that are more exposed than on IFS, are the actual diff (pumpkin) and the prop shaft and if you choose your lines over/through obstacles properly, they should not be a compromise. At least you know the clearance below these items are always constant, unlike on IFS where it varies with suspension movement. The transfer case of a live axle vehicle is no more exposed than that of a vehicle with IFS.

The main advantage of a live axle is ARTICULATION, however and articulation provides better traction, which apart from allowing better progress, protect the mechanical components of your drive train. Spinning wheels that suddenly get traction, break things.

The ideal would be IFS like that used on the DAKAR type racers, but it is impractical for a road vehicle, as the suspension wishbones are attached in the centre of the vehicle to allow the required articulation. And have you seen the body roll on some of those ?

[Biggles]

Articulation.
Over 2 inches lift is difficult for IFS and you have an suspension that is not at optimal position.
Pumkins are tough.
Live axles handle abuse better.

[Zombicon]

I have never seen an IS damage anything that aborts the trip.
Keith

Those Side shaft's and CV's when lifted get's worn out a lot quicker ,
you may ask Sakkie.. he knows... A CV Shaft is not as strong as a solid diff in standard form.

[offroadrover]

Some of the best off road vehicles in the world have independent suspension. Is this not like the debate held 40 years ago when people debated leaf springs vs. coils or electronic ignition.

I am no engineer but do believe independent will win in the end, please don't shoot me. It can respond better to changes in surface such as corrugated roads where the higher unsprung mass of the solid diffs can cause the wheels to bounce and braking traction. If the control arms are long enough then axel travel can be phenomenal, like the Dakar racers mentioned.

[ThysleRoux]

Some of the best off road vehicles in the world have independent suspension. Is this not like the debate held 4 years ago when people debated leaf springs vs. coils or electronic ignition.
I am no engineer but do believe independent will win in the end, please don't shoot me. It can respond better to changes in surface such as corrugated roads where the higher unsprung mass of the solid diffs can cause the wheels to bounce and braking traction. If the control arms are long enough then axel travel can be phenomenal, like the Dakar racers mentioned.

Oh I'm sure IFS will win, not because it's the better off road system - but because it makes better on road handling easier and cheaper to attain. OffRoadRover, corrugated roads are NOT off road situations.

As mentioned, the off road RACING vehicles with IFS are amazing, but the set-up is totally impractical for a road vehicle. There is just not enough room under a normal vehicle for the massive wish bones. There is also a huge difference between off road racing (Dakar / ABSA off road series style) and off road driving.

[offroadrover]

Thys,

When all are cars are electric with independent hub motors on each wheel on independent suspension we will have no more pumpkins.

[ThysleRoux]

Thys,

When all are cars are electric with independent hub motors on each wheel on independent suspension we will have no more pumpkins.

[offroadrover]

Believe it it is coming.

[Megagustodon]

With the torque you get out of direct drive DC motors those things will go anywhere. It's just the batteries that they have to sort out....




But......





there is a lot to be said about the roar of a proper internal combustion engine...

[Fluffy]

Those Side shaft's and CV's when lifted get's worn out a lot quicker ,
you may ask Sakkie.. he knows... A CV Shaft is not as strong as a solid diff in standard form.

Hi,

I was referring to an unmodded IFS.

Also although the IFS CV shafts arent as strong, they are normally not exposed either. They are usually protected by the suspension (Wishbone?)

Yes I agree that the solid axles gives the ultimate in articulation, its just that as far as compromises go the IS systems seem to be getting to the point where, unless you are doing pretty extreme stuff, I THINK I prefer IS as in D3/4 etc. Everything is tucked away, the props are fixed ie they dont move and change length etc etc.

With IS normally the worst you can do is slide on your smooth underbelly if you make a mistake. This to me is especially usefull for middle mannetjie type overlanding. With my solid axle car I am permanantly in fear of a rock or something hidden in middle mannetjie or on smooth level surface where the underlying terrain is obscurred.

Again for extreme cross axles and rock crawling solid axles, but for general overlanding, tar mmmmm.

Another thing that scares me with solid axles are the axle mounting points for the shocks. Often when driving behind some bakkies you can see the mounting points for the axles stick out 50-100mm below the axles.

Cheers
Keith

[ThysleRoux]

Hi,
I was referring to an unmodded IFS.
Also although the IFS CV shafts arent as strong, they are normally not exposed either. They are usually protected by the suspension (Wishbone?)
Yes I agree that the solid axles gives the ultimate in articulation, its just that as far as compromises go the IS systems seem to be getting to the point where, unless you are doing pretty extreme stuff, I THINK I prefer IS as in D3/4 etc. Everything is tucked away, the props are fixed ie they dont move and change length etc etc.
With IS normally the worst you can do is slide on your smooth underbelly if you make a mistake. This to me is especially usefull for middle mannetjie type overlanding. With my solid axle car I am permanantly in fear of a rock or something hidden in middle mannetjie or on smooth level surface where the underlying terrain is obscurred.
Again for extreme cross axles and rock crawling solid axles, but for general overlanding, tar mmmmm.
Another thing that scares me with solid axles are the axle mounting points for the shocks. Often when driving behind some bakkies you can see the mounting points for the axles stick out 50-100mm below the axles.
Cheers
Keith

Those mountings may look vulnerable from behind, but are normally very tough and can take quite a pounding. They are also close enough to the wheels to be out of harm's way most of the time. To me the lower control arms/wishbones of an IS (front or rear) look very vulnerable, again. They are normally lower than the axle tube on a live axle and are a lot less robust.

Keith for overlanding, you may have a point, but that's not off roading. And with proper design, live axles can be made to behave quite civilised - the WJ's on road behaviour is enough proof of this.

[Fluffy]

Keith for overlanding, you may have a point, but that's not off roading. And with proper design, live axles can be made to behave quite civilised - the WJ's on road behaviour is enough proof of this.

Hi Thys,

Thats probably the point I was subconciously trying to make.

For example I am doing the River Trip this year and to me, body damage asside, taking the P38 instead of the RRS is a no brainer.

Another factor not mentioned often is speed. Very often (apart from dune driving) the conditions where live axles excell are low speed stuff and vice versa.

Interresting non the less. Would love to revive this conversation in 10 years time.

Cheers
Keith

[ganymede]

Hi,
With IS normally the worst you can do is slide on your smooth underbelly if you make a mistake. This to me is especially usefull for middle mannetjie type overlanding. With my solid axle car I am permanantly in fear of a rock or something hidden in middle mannetjie or on smooth level surface where the underlying terrain is obscurred.

Done a trip with IFS Mazda 4x4 in Zambia. Problem is that your clearance is not constant with IFS. On many occasions when you hit a bit of a bump in the road it would bottom-out against the middlemannetjie. The bashplate took quite a beating, and eventually whatever it was protecting would have suffered. With SFA, the height (from middlemannetjie to axle/pumpkin) remains far more constant. Many similar vehicles with SFA traverse the same roads and on occasion you just graze the middlemannetjie.

Nice additional thing about Land Rover is the offset pumpkin. You graze even less!

[Oppers]

I believe Thys has it spot-on.... It's all to do with weight and costs.

Maybe not the scientific answers you asked for, but IMVHO it's not unlike footwear. There are thousands of general sneakers sold for every pair of proper running shoes, as it's easier and cheaper to produce. But when the running gets serious, what would you rather wear, a set of Nike Air's, or a set of North Star's...??

Obviously the general use of 4x4's dictate where the general designs will go, and in general there are more 4x4's being used in non-off-road situations than in serious terrain.

But when the chips are down, I'd rather have Solid Live Axles front and back (and live with the downside on tar) than Independent Axles when the going gets tough.

[ThysleRoux]

Keith I agree wholeheartedly re the speed thing. But that's where I believe the answer lies - you have to decide if you want to compromise on or off road.
In 10 years time I doubt if there will be any new LFA vehicles on the market. AFAIK it's only the Defender, Wrangler, the antique Broozer model and Jimny at the moment, anyway.

[mnrvermaak]

A sense of possession turns sand into gold.
The people who drive solid axle all round will say the on road handling is not that bad (yes it is...)
The people with IS will say articulation is not that important for off-road driving (yes it is...)
Diff-lock and traction control can reduce the necessity of good articulation but nothing can make a vehicle with a high unsprung weight handle better.

All-round, IS will win every time.

[Tony Weaver]

Nice additional thing about Land Rover is the offset pumpkin. You graze even less!

Uuum yes, it sits exactly below the driver's uum ... anyway, I steer by the seat of my pants.

[ThysleRoux]

Done a trip with IFS Mazda 4x4 in Zambia. Problem is that your clearance is not constant with IFS. On many occasions when you hit a bit of a bump in the road it would bottom-out against the middlemannetjie. The bashplate took quite a beating, and eventually whatever it was protecting would have suffered. With SFA, the height (from middlemannetjie to axle/pumpkin) remains far more constant. Many similar vehicles with SFA traverse the same roads and on occasion you just graze the middlemannetjie.
Nice additional thing about Land Rover is the offset pumpkin. You graze even less!

You see this on most IFS 4x4's that are used off road regularly. The tupperware lower grille of my Jeep is still undamaged, because the live axle does not allow as much body/chassis bounce as IFS.

[Fluffy]

New Design - thank you DeBono.

Dont motorbikes have solid axles AND independant suspension?

What if you take two bikes and weld the frames together with cross beams.

Then you have four wheels with solid axles and independant suspension.

Hows that for lateral thinking, literally. Rotate the suspension by 90 deg. Suspension pivot points are in line with the vehicles axis.

mmmmmmm Wheres Apoc.

Cheers
Keith