IFS vs SAS

Aido · Jan 21, 2010

The story so far.....as taken from...... http://www.navara.asia/diy-modifications-build-ups/1625-my-d22-go-whoa.html

Aido said:
That is a great pic.
Makes me wonder though. Is articulation more beneficial than ground clearance? From the pic above it would seem that aside from being able to keep both wheels on the ground the whole effort is hobbled somewhat by not achieving any further ground clearance.
Not wanting to piss on the parade or anything but if you were to be in some modest ruts wouldn't you just drag the diff through and possibly lose all traction through grounding it? Then follows the rear diff until the rear loses traction and leaves you high and dry?
Is this why IFS came about but that it just has too limited travel?
I know this is your build up thread but perhaps between you and Joshy you could explain why it is necessary in another?

08KINGCAB said:
You need articulation for grip, you don't move when the wheels don't touch the ground. ground clearance from bigger tyres to get those diffs up as you mentioned results in needing to lift the body to clear the bigger rubber.

Aido said:
Yeah but.....

If the diff lifts both off the ground then where are you?

"Hello cat.....have you met my pidgeons?"

SOLID D22 said:
The lowest point of the front diff is the diff centre itself, with ifs the whole arm holding suspension is in the way, also go over a decent bump in the tracks(this is slow off roading) and if you bend your torsion bar itl be a slow drive home as that torsion bar will be doing nothing at all.

The amount of drop a solid front end enables you to have means a 5ft rut is no problem to attempt, depending on setup and shocks used, but with ifs even if you lift it 4inch the susp arms are still bolted to the same point of the chassis so the flex is almost the same as stock, you just have a raised looking car, which is better for clearance but actually no real off road flex improvement.

Aido said:
Thats what I was getting at.
There is still a plane between wheel centres where obstructions will impede your travel though ( the diff and its centre)

SOLID D22 said:
Yeah the centre is always going to be in the way unless you fit bigger tyres or there is a gear system that bolts onto your hubs which give you a few maybe more inches of lift without fitting tyres. Ifs limits your travel but solid front end with coils not leafs is unlimited travel depending on shocks, i think iv just repeat myself there.

Aido said:
Fuel to fire.

Have these been considered? Nissan Portals

SOLID D22 said:
There not cheap, not at all.

Aido said:
I believe about 18 large I know.
Still its worth considering for those that want to go to extremes.

08KINGCAB said:
A necessary evil on a road reg 4WD, you have to compromise.

joshy said:
offroad is all about diff clearance and keeping wheels on the ground. More articulation will give you more traction, but does nothing if your sitting in 2 wheel ruts and the mound inbetween is hitting your pumpkin. thats when you either back up and hit it harder and use the diff as a plow or go home and put bigger tyres on and cut guards. portals would be awesome but then youll want to reset up your suspension to keep the overall height down.

joelus said:
Im going to get in on this argument....

IFS sucks.... there.

everything these days (hilux, navaras, rodeo etc etc) are all IFS because its cheaper for the manufacturer to make. They dont give a crap about articulation or offroad capabilties... not like they used to anyways...like my GQ having swaybar diconnects standard and range rovers and patrols having switchable diff locks! they make there vehicles cheaply for the tradie. SAS has way way more potential, as has been previously stated, IFS gets jack all articulation. How many comp trucks do you see with IFS?? none. cause it sucks. thats why joshy and solid d22 go all out as they do

Portal axles are wicked bit of engineering, check out the next army truck that drives past you they all use them. but like joshy said you have to lower your suspension if you have a big lift, keep it to 2" or so. I think having portals with 35's is equal to having 44's as to the clearance of your pumpkin off the ground. big dollars though.

SOLID D22 said:
IFS does suck for off roading, but most people who are serious about 4wding would have opted for a car with solid axels and coil springs all round in the first place. When i bought my nav i had no clue to 4wding but after learning about it over the years, if i knew then what i know now i would have bought a patrol.

Aido · Jan 21, 2010

do you lot know this is now a 11000 word essay?

Pro-Nav2.7TDi said:
Slow down, you're shooting from the hip there. IFS is very complex, it's certainly not cheaper to make. Why do all those millions of little Suzukis have solid axles? Because solid axles are cheap. IFS gives better NVH and handling on road and handles high speed offroading better. I don't like this fact any more than you but only 0.005% (I made that up) of everyone who buys a Navara, Rodeo, Hilux actually takes it rockcrawling so pandering to a market that isn't there would be foolish. It's a commercial vehicle that just happens to have an added 4x4 feature to allow you to traverse worksites, go camping on the weekend etc.

It's not that they care less about off roading capability than they used to. The market just cares more about on road manners. The Navara has never ever had five link coils or a solid front axle in its whole history so there's no betrayal like there is with the Hilux.

A dual locked IFS vehicle with 2" lift and mud tyres aired down would be plenty capable for even the top 2% of the market. If you told Nissan you wanted the Navara to have a solid front axle they'd tell you you wanted to buy a Patrol cab chassis. The real marketing mistake is in not building a dual-cab cab chassis coily Patrol. If they made one of those in the 80s I know I'd have one of them and not a Navara.

SOLID D22 said:
Not a navara, JUST, but datsun had the ute with a solid front end 4wd system.

Pro-Nav2.7TDi said:
Which one?

joshy said:
dont think nissan/datsun have ever had a dual cab solid 4wd. And only the various patrols have had a live axle.

IFS is better offroad, just to get it to that stage where its better costs more $$$$$$$

joelus said:
oh yeah i agree that they are better handling, ofcourse, but we were talking offroad capabilties, going through rutts etc... and the potential for SAS is virtually limitless, please refer to joshys truck but ofcourse a manufacturer is going to cater for the main client base, otherwise they would go broke.....

pretty certain 720's if thats what youre thinking of, are IFS, patrols are the only ones... well except for the nissan titan, not delivered to Aus, are the only solid fronts.

Yeah we are hacking solids thread but hey it keeps us occupied until his next step! It would make a long winded endless debate, where SAS would win hands down, as far as offroaders are concerned to be politically correct!

and aido you started this just trying to help you see the light

SOLID D22 said:
My father in law has an old mate who was a concreter and he had this datsun ute im talking about, the one with 4 square headlights, i remember it being 4wd and being a solid front end. But now you guys have made me doubt myself so before i make an arse of myself il find out what was on the car for certain, if he has still got it.

joshy said:
sorry should have made my last remark more clear. IFS is better for hardcore offroad.

Jason said:
If you are talking unlimited $$$ and imagination then IFS is better for either. In any 4wd application how could front wheels acting independently of each other NOT be better? Solid front ends are better when compared to "off the factory floor" setups and are cheap when compared to some of the more extreme mods/build ups. Case in point: (I know it's extreme but it IS an IFS system in it's most brutal form)

YouTube - Chainlink extreme 4x4

SOLID D22 said:
That car is nuts but lets not get it confused, it is an ifs setup but its not ifs as we know it, it is completely different and any ifs set up as we know it will never compare to a solid front or rear application.
Iv seen some pretty good flex from solid comp trucks too, nothing in comparison but not far off to that vid but what that vid does prove is the way the arms are working on that car is exactly the same as a solid axle car with radius or trailing arms. Seemed like it had hydraulic suspension too.

Old.Tony said:
There are other considerations between solid axles and IFS.

When one wheel on a solid axle rises, the angle of that wheel changes in respect to the horizontal. With an IFS, the angle remains constant. This means that solid axles at their extremes present just the corner of the tyre to the ground, which not only reduces traction but can cause damage to the tyre wall. IFS doesn't do that.

That being said, without drastic changes to any SUV, the solid axle will articulate further than IFS because the range of the arms supporting the wheel in IFS is limited vertically. In order to increase that range, the length of the arms needs to increase and you've only so much space to play with there - that's why the IFS of the car in the video was completely translated around.

Each has its benefits, and if you could fit rounded tyres to a solid axle you'd overcome their major drawback as well.

SOLID D22 said:
Well said.

joelus said:
i think we are all agreed that IFS in its absolute extreme set up, is better ofcourse...and that rig on youtube, take note of the point that suspension is connected, its like independant swing arms off the centre of the car not a traditional road set up by any means, the amount of work needed to get IFS to match SAS for capabilties and cost, is nowhere near the ball park. hence why all comp trucks have solid axles, and why guys all over the world pull out the IFS and convert to solid axle. ...well because its better...and can be done legally and get way more out of the truck.

Jason said:
Most, if not all Dakar setups are IFS, different type of off-road racing though. And the King of the Hammers comp had a couple of IFS setups last year (more traditional set-ups, not like the youtube vid), will be interesting to see if there is more or not this year.

Just want to mention that I am neither pro IFS or Solid Axle, it's horses for courses, there is no doubt that a solid axle gives best bang for buck for Joe Average (not saying you're Joe Average.)

.

joshy · Jan 21, 2010

I think youll find there are ifs setups like the chain link. well kinda. having the struts move up and down along the body removes alot of issues as the arms can be alot longer. altho your cvs will still be an issue. which is when you run more then 2cvs on the shaft to make up the angles.

SOLID D22 · Jan 21, 2010

The concreter guy my in law knows has gotten rid of his old truck so i cant confirm if it was a solid front end or not, but i dont know much history on those old trucks so if you reckon they didnt come out with a solid front end then i believe it.

joelus · Jan 22, 2010

I think if i was building a dakar racer i would go IFS, purely for comfort while your hurtling along at 160k over some desert! But if i wanna build a 4wd to be majorly capable offroad but still be road registered definitely stick with the SAS! That buggy is pretty wicked, but Ive seen alot of SAS trucks with hydraulics that can get through that same terrain just as easy... and alot easier to build... thats my argument. As the conventioal syatem of Idependant Front goes, it just doesnt have the articulation or even the potential that solid does. Its science :big_smile:

SOLID D22 · Jan 22, 2010

joelus said:
I think if i was building a dakar racer i would go IFS, purely for comfort while your hurtling along at 160k over some desert! But if i wanna build a 4wd to be majorly capable offroad but still be road registered definitely stick with the SAS! That buggy is pretty wicked, but Ive seen alot of SAS trucks with hydraulics that can get through that same terrain just as easy... and alot easier to build... thats my argument. As the conventioal syatem of Idependant Front goes, it just doesnt have the articulation or even the potential that solid does. Its science

I agree, well said.

ants_oz · Jan 22, 2010

joelus said:
....As the conventioal syatem of Idependant Front goes, it just doesnt have the articulation or even the potential that solid does. Its science

I don't want to take this too far out of context, but I must disagree.

Look at vehicles like the D3/D4 Discovery - proven to have better cross axle
articulation than previous generation live-axle (solid axle) Disco's. If you are a "numbers person", then research will show you greater quoted wheel travel for the all-independent suspension D3/D4 compared to previous generations.

Similarly Range Rover Vogue - has more travel and also better articulation than previous recent generations of range rovers.

SOLID D22 · Jan 22, 2010

IFS cannot flex like a coil sprung solid car can. Period.
As stated before its science, its just not possible, you have to remember ifs is fixed to a point of the chassis on the car with the ifs arms only about roughly 400mm to 600mm long, where as radius arms fixed to underneath more centre of the car have in most cases 1m of radius arm and have no limit of flex as that depends on the type of shocks used.
If you use a good long travel shock on ifs it still has the problem of being hindered by being bolted to the chassis and that not letting it drop to be able to flex.

I have no doubt that car makers will make ifs better and better as time goes on but facts are facts.

ants_oz · Jan 22, 2010

SOLID D22 said:
IFS cannot flex like a coil sprung solid car can. Period.
As stated before its science, its just not possible, you have to remember ifs is fixed to a point of the chassis on the car with the ifs arms only about roughly 400mm to 600mm long, where as radius arms fixed to underneath more centre of the car have in most cases 1m of radius arm and have no limit of flex as that depends on the type of shocks used.
If you use a good long travel shock on ifs it still has the problem of being hindered by being bolted to the chassis and that not letting it drop to be able to flex.

I have no doubt that car makers will make ifs better and better as time goes on but facts are facts.

I disagree. But then that is democracy at work

Again, all I can do is point to the evidence of the situation with the current Discovery versus previous (D1 and D2) iterations. The IFS (which according to you can in no way possible flex more than the live axle) does indeed flex more than the live axle versions. Fact.

Comparing a live axle to an IFS is near on impossible to do - unless you look at examples such as 100 series Landcruiser which was available from the factory in both configurations - IFS on some models in the range, live axle on other models in the range. On that example, yes, the live axle had better front end articulation.

But when talking about such things as vehicles which have had conversions to solid axle, or buggies with all independent...or whichever modification you choose to discuss - the sole determining factor will be the depth of the pockets of the person doing the build.

Jason · Jan 22, 2010

ants_oz said:
the sole determining factor will be the depth of the pockets of the person doing the build.

Quoted for truth.

SOLID D22 · Jan 22, 2010

OK i guarantee my left nut that my car front end will flex way better than any ifs setup out there driving on the road registered.

Who's up for the test?

Who will back me up?

Iv had 3 wheels still touching the ground while my rear tail light was above my head height, where as in previous ifs models i shit if i go over a speed bump (nah just kidding) but seriously iv never been in a car with good ifs flex, this includes my mates hilux which had a snake racing kit installed, i think it was a 4 inch lift, did not flex no were near as much as my car.

See i wasn't lying 3 wheels still on the ground and the car is flat as a tack no body roll.

SOLID D22 · Jan 22, 2010

Sorry car sits flat here with the coil overs doing the work not the stupid leafs.

Once again headlights are as high as my head.

Car can flex more too, these photos are just to see how far i could get with 3 wheels still touching the ground.

ants_oz · Jan 22, 2010

Yours is a heavily customised and modified vehicle.

I refer to my previous comment where I inferred that the outcome will be directly relational to the depth of the pockets of the person building/owning the vehicle...

I mean no disrespect when I say this - you are proud of your vehicle and what you have achieved with it. It has been modified to achieve what you want to achieve. But believe me - there are some VERY interesting vehicles out there with independent suspension, which are registered for on-road use.

Off the shelf products from companies like Snake Racing (for your mates hilux) - which seem to peddle quite a range of illegal modifications for road going vehicles - are hardly a fair comparison for your vehicle...a solid axle swap for a navara is a technically complex piece of engineering with a great deal of customisation involved and likely very few if any, off the shelf bolt-on parts involved.

Jason · Jan 22, 2010

You just added a limitation then Stef, who has ever mentioned road registered?

Generally speaking, when taking into respect availability to average Joe, Solid Axle will articulate better and IFS will ride better. No-one has disputed that.

KraftyPg · Jan 22, 2010

SOLID D22 said:
OK i guarantee my left nut that my car front end will flex way better than any ifs setup out there driving on the road registered.

Breath a sigh of relief you left nut is safe for now

joshy · Jan 22, 2010

KraftyPg said:
Breath a sigh of relief you left nut is safe for now

For now. Build up on outerlimits of an ifs buggy that will be road rego.

SOLID D22 · Jan 22, 2010

OK till an IFS truck is posted up here which im sure it will be soon by someone il keep my left nut thanks.
Also so far as it goes my car is not heavily modified, its not engineered its an off the shelf product, 99% bolt on and cost a tiny fraction more (not much) to buy the actual kit than an ifs lift kit.

Also to clear things up i think were gona have to somehow compare road registered to non registered cars and low cost to big dollar projects.

Anyway im willing to say a stock patrol will flex better than any stock ifs car you can think of. So if you had the same funds to spend on both cars the solid would still come out on top in the end.

With the extreme ifs setups you guys are talking about besides the engineering masterpiece in the previous posts(which was not a car), so lets keep it car related please, can someone post a link or photos of one flexing if anyone has any.

ants_oz · Jan 23, 2010

I'm interested to know how you can claim conversion from an independently sprung front end navara to a live axle is a bolt on conversion... I'm a qualified mechanic - knowing a thing or two about the various setups, I would hardly call it bolt-on.

And as for not being engineer approved??? You have undertaken a modification to the suspension configuration of the original vehicle - that requires engineer approval.

I notice your vehicle has number plates on it - which I can only presume means you drive it on the road.

I'm not going to get into the morals of driving an unapproved vehicle on public roads - that is your choice to make.

And since I have a HUGE problem with people knowingly making illegal or non-approved modifications to their vehicles, I am going to leave this thread alone before I say something I regret.

A person I knew closely was killed in a motor vehicle accident, where another vehicle lost control and hit them. The other vehicle was modified to a degree that it required engineering approval, but engineering approval had not been undertaken. At the coroners inquest, the owner of the other vehicle assured the court that their workmanship was top notch. An automotive engineer who inspected the vehicle's modifications deemed the vehicle unroadworthy, and incapable of receiving engineering approval due to several major engineering problems.

I'm NEVER going to support ANYBODY who thinks they are above the law with regard to vehicle modifications.

the_bluester · Jan 23, 2010

Ants, I think I would have to say that you are picking at language not technical detail there.

"its not engineered its an off the shelf product" does not say to me that it has not been designed and engineered properly to be able to be certified. It says to me that this is a product that has been designed and engineered and produced as a kit, just not engineered and custom built for one customers car only (While I have no idea, Solid D22's car may be the engineering test bed for the kit)

Leprechaun · Jan 23, 2010

Lets clarify that just because a purchased part bolts on rather than being welded it may still need approval by an engineer.

IFS vs SAS

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