SAS's seem to be a pretty expensive and difficult procedure... what are the advantages and disadvantages to getting one done?

Well, going just about anywhere a normally solid front axle equipped vehicle would go, that would leave the IFS guys hung up.

I've run IFS now for a while, but normally I've had SFA equipped vehicles. I can definately feel the difference, and I have to take different lines on the same trails that I used to tank over with little to no regard to my vehicle's abilities.

SAS, hard core mod for the guy that wants it all, and drive it too.

Articulation and durability. 'Nuff said.

so the solid axle basically allows both wheels to be touching at all times which makes it easier to crawl? whereas the IFS absorbs bumps/ less flex and is more prone to breakage?

but on the other hand would the SAS'ed vehicle perform horribly in something like desert racing?

Pretty well sums it up...except for the breakage part. It all depends on how it's built though. But yes, solid front axle for huge rocks, IFS for everything else...especially desert racing.

IFS on everything else? Huh? There really isn't anything IFS excels on when compared to a solid axle truck when the speeds are say lower than 20 mph or using 4LOW. Desert racing yes if you have the IFS set up with the right aftermarket parts, straight from the factory a solid axle rig is built a lot stronger but still doesn't make for a good desert racer.

Next time you are out wheeling with some guys with solid axle trucks ask to try the SAME LINE you just did with your X, try something offcamber if you can with some rocks. The Oh-Shit feeling you get with the IFS is practically gone, you will quickly see the benefits of a solid axle truck offroad.

I'd have to agree. Solid Front Axle is more durable and works better at low speeds. The thing is that with the SFA you have more unsuspended weight, so when you hit a bump (big or small) more mass travels up and down. That mass has to be sprung back to position and damped so the wheels don't start jumping all over (loosing control). So at higher speeds (more bandwidth required) the IFS works better. You can feel the difference driving on any road.

I have IFS now, will do the SAS at some point in the future (and I mean future). I had a SFA on my LandCruiser and it never slowed me down, I guess SFA is the way to go if you do any off-road (except desert running, maybe).

Hope this is helpful.

Difficult.. Not at all.
Expensive.. compaired to what?

Than why the hell's everyone getting SFAs?

That's why I wheel

Read the whole thing I wrote, it was about driving the same off camber rocky line with an IFS vs SFA truck.
With a SFA you have many, many more lines to choose from and much harder trails to try to give you the Oh Shit feeling.

Nah, I'm with ya' . I've wheeled both. I'm just bein' silly.

Not trying to start the old SAS vs. IFS debate again. It was just an opinion.....

....that happens to be from an article in one of my offroad mags. I just happen to agree. I know most of you don't so let's just save the typing for something constructive like why we all get crappy MPG.

Ok, I don't kno why my physicy bain never thought of that! once I read your post a light went on in my head and I smacked my forehead and went, oh yeah, duh!!!

In stead of just saying more articulation I will add that a solid axle acts like a lever. When one wheel goes up it will actually push the other wheel down. For example if you put the FR tire up on a rock, it acts as a pivot point for the rest of the axle, where the springs/weight of the truck pushes the FL tire futher and further down., aka droop. IFS cannot do this in anyway shape or form (well, time and $$$, maybe)and therefor cannoy articulate the same as a solid axle.

Warning long post/explination

That said IFS can absorb an impact and not effect the rest of the truck as much as a solid axle. Impact being the key word "An impact force is a high force applied over a short time period. Such a force can have a greater effect than a lower force applied over a proportionally longer time period." -- wikipedia

That being said an impact force can only be generated if the vehicle is moving at speed. Do a simple test some time. find a rock, preferably one that won't blow a tire at speeds. first off go over the rock slowly. You'll notice the front suspnsion on the X doesn't really do much, in fact it causes the body of the X to tilt a little bit, now when the rear tire goes over the rock you'll notice the body stays more level but the suspension is working. Now do the same thing but goign faster, you'll notice when the front goes over the rock/bump not much happens (unless the rock is too big) because the suspension obsorbed the impact, when the back goes over you'll notice little ripples, which is what jjrasta described.

So yes, independant suspension is made for high speed impacts like normal driving and highspeed racing (ie most applications) while a solid axle is made be more manuverable, which works very well at slower speeds, which might be where the term "live axle" comes from. Also since the IFS is designed to obsorb impacts we can't really say it isn't as strong as a solid axle, the drivetrain perhaps but not necesarily the suspension.

Anyways, report due back friday after class.

I think the durability thing is more related to an IFS having two half shaft set ups, rather than one long one...

...not talking about the shafts themselves per se, but that the entire force is applied to a smaller structure (One tire say), which is a control arm braced set-up.

On the live axle, the entire axle can take the hit..

Of course, at higher speeds, the entire axle taking the hit causes some steering to occur that you didn't want, etc...

At lower speeds, the IFS is still able to be putting all the force on one tire, and if you've ever watched an IFS rig climbing a hill, etc...and seen the tires alternating getting ahead of one another like they're racing or something...you can see the stress the front end is under.

The control arms on an IFS are pretty much lateral, so forces fore-aft, such as impacts, are taken at the joints where they pivot from.

On a live axle, there's none of that...the axle itself is taking most of all the punishment...and the control arms are running more fore-aft than laterally, and are typically better positioned to take forces in that direction.

The opposite force articulation mentioned is very important as well...on an IFS with a hung tire, the planted tire has what ever weight is on it to hold the X up...but no leveraged downforce as provided by the live axle.

So - Yeah, the live axles are king on the rocks and off camber, etc....and IFS is best for higher speeds.

If the control arms are perfectly lateral the tires will move forward and backwards, a leaf sprung live axle will move forward and backwards more than IFS due to the shackle compressing, moving one end of the leaf spring back farther, 4 link on the other hand... Also the "hinge" of a leaf sprung live axle is in front of the axle, which will cause the axle to move forward, ever heard of flex steer? Although the X doesn't encouner this.

One problem with the argument that a control arm is a smaller structure, which means less torque in placed on the joints because they aren't as long as a live axle. Did you ever play the game as a kid where one person holds a pencil, another keeps breaking it in half untill they can't break it in half any more. Do that and you'll definately notice the smaller peices are harder to break than the whole pencil.

Also don't forget that as a tire is rolling it acts as a sort of ramp/wedge, plus it's rolling and a rolling object that has fore-aft forces is slipping, well there is always some slippage but it's negligable Do you have any video's of the front tires "racing?"

BTW I really enjoy these kind of technical discussions, it's rather nice TJ.