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Which is better and why? IFS vs. Solid Axle

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Old 12-17-2007, 07:37 PM
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Question Which is better and why? IFS vs. Solid Axle

I have been wondering the lately. I know the FJ an H3 come with IFS in the front. Why is this design inferior to the solid axle in the front of wranglers? This is an honest question, and I have been wondering for a while. Please dont flame.
Thank you,
Ryan
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Old 12-17-2007, 07:49 PM
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IFS is better for an on road ride and handling characteristics at higher speeds. Solid axles are better for durability and off road characteristics at lower speeds, most importantly great articulation. The solid axle is better for off road because the two sides are tied into one another. When one tire is pushed up, the other tire is pushed down, which is better to keep tires planted on the ground/obstacles.

Of course this is not the case for every vehicle. There are some very fast off road solid axle vehicles. I don't have a ton of knowledge on this, it is just my general understanding. There are people here who are much more knowledgeable! I hope this helps!
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Old 12-17-2007, 08:02 PM
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the main thing is flex or articulation. With a solid axle your fulcrum, if you will, is mid point on the axle meaning each tire can go equal distance in opposite directions giving max flex. With IFS your fulcrum is about 3/4 point of the line (where a solid axle would be) so you can get much flex out of the system.

Now this isnt to say all IFS suck. We have an 03 Ranger who wheels with us, solid axle rear, IFS front and its pretty good at getting through the obstacles.

Now i hear IFS can break parts easier but i only hear so take that for what its worth
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Old 12-17-2007, 08:17 PM
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Theoretically IFS should be better. With the right design the tire tread will be flat on the ground at all articulations. In reality the solid axle is more reliable, less parts, more rugged, not so spindly, and can carry quite a load.

I don't remember all the particulars, but the end result for me was decided years ago, solid axles are best. Just my 2 cents.

But then watch a fully independant long armed spindly totally tubular dune buggy with one humongous V8 virtually flying through everything and you will have second thoughts.
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Old 12-17-2007, 10:20 PM
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IFS is actually superior in many ways. For one, the differential is up and out of the way. No Pumpkins to worry about! Also, handling characteristics on road are much better, as well as off road. Articulation-wise, I think with the right set up, you can get better articulation with an IFS than a solid axle. Look at BAJA racers. Those things have feet of articulation (mainly due to triangulation and long arms).


The biggest problem with IFS is cost. They need more parts, so they cost more. Also, more parts means more potential for breaking.

Modifying independent suspensions gets a lot more expensive too, so your lift kit will cost you MUCH more. Also, they're harder to work on. One of the biggest questions with the design of the current Mustang was Indepentent suspention or solid rear axle. Cost reasons, and the request of weekend mechanics encouraged the team to build a solid rear axle platform.
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Old 12-18-2007, 01:59 AM
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IFS is better when properly designed, look at the HMMV or the Baja trucks. Most are designed for cost and a nice ride though. Not to mention a straight axle is simple, easy to fix, hard to break, and cheap.
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Old 12-18-2007, 06:33 AM
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go look at lift prices for the liberty or anything IFS for that matter, You wont complain about our costs after that.
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Old 12-18-2007, 07:52 AM
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Originally Posted by CIJeep View Post
Theoretically IFS should be better. With the right design the tire tread will be flat on the ground at all articulations. In reality the solid axle is more reliable, less parts, more rugged, not so spindly, and can carry quite a load.

I don't remember all the particulars, but the end result for me was decided years ago, solid axles are best. Just my 2 cents.

But then watch a fully independant long armed spindly totally tubular dune buggy with one humongous V8 virtually flying through everything and you will have second thoughts.
Originally Posted by wayland1985 View Post
IFS is actually superior in many ways. For one, the differential is up and out of the way. No Pumpkins to worry about! Also, handling characteristics on road are much better, as well as off road. Articulation-wise, I think with the right set up, you can get better articulation with an IFS than a solid axle. Look at BAJA racers. Those things have feet of articulation (mainly due to triangulation and long arms).


The biggest problem with IFS is cost. They need more parts, so they cost more. Also, more parts means more potential for breaking.

Modifying independent suspensions gets a lot more expensive too, so your lift kit will cost you MUCH more. Also, they're harder to work on. One of the biggest questions with the design of the current Mustang was Indepentent suspention or solid rear axle. Cost reasons, and the request of weekend mechanics encouraged the team to build a solid rear axle platform.
Originally Posted by Jrgunn5150 View Post
IFS is better when properly designed, look at the HMMV or the Baja trucks. Most are designed for cost and a nice ride though. Not to mention a straight axle is simple, easy to fix, hard to break, and cheap.

Like they said, IS (idependent suspension) is better all around then a solid axle. they have better on road ablities at low and high speeds. A properly tuned IS will exceed a solid axle in flex and ablities. The problem is cost. One of the main reasons a solid axle is so popular is because they are easy to lift, easy to repair, and easy to maintain. Also, one reason a lot of people don't like factory IS's is because its usally hard to disconnect the sway bar. and as almost all of us can testify to, there is a big difference in flex of a disconected and a non disconnected setup. the same goes with an IS system, a disconnected one will flex a whole lot more then a connected one.

This is one reason you see so many H1's, H3's, chevy's, etc with one wheel in the air. because they don't have the ablity to disconnect. I know there are kits out there, a buddy of mine has front disconects on his chevy S10, so it can be done, just most people don't. Baja racers usally don't even bother with a sway bar because they won't be on the road, so there is no need.

Car companies put IS's on the front and solid on the rear of trucks and mid-size SUV's so that they can still have good handling dispite their wieght, and also have that pulling power. a solid axle can be built for pulling for a far cheaper price then a IS can. Thats not to say the solid axle is better, its just cheaper. Proof that an IS can be built for towing is the H1 which has IS all around and can pull over 9000lbs.

Solid axles are strong and can take a beating naturally, but just like an IS setup, depending on the way its designed will determin how tuff it is. a Dana30 will not take the same punishment as a Dana60 will, like wise, a IFS system off a geo tracker will not take the same punisment as the IFS off a chevy 2500. The problem is, like everything else, cost. it cost more to beef up an IS system then it takes to beef up a solid axle.

The only thing a solid axle is better at then an IS, is the cost, that's it...
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Old 12-18-2007, 04:28 PM
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In order to answer the question of which is better, one must first determine what it is to be used for. IFS compared to a solid front axle is like comparing an apple to an orange.
On a vehicle that is intended to travel highways at high speeds, and provide a very comfortable ride for the occupant, then IFS would be the ideal setup. That is exactly why IFS was desinged. IFS provides much better handling on most roads and highways, even if those roads have Pennsylvania Potholes. IFS will allow better handling on these roads in both high and low speed conditions.
IFS is also good for offroad driving, providing the terain is such that the travel of the suspension is not exceeded to the point where a tire leaves the ground.
Once a tire leaves the ground, unless the front differential is locked in some manor, both tires are usless, as there is no traction. Granted most 4wd vehicles with IFS still have the rear tires pushing, so in some instances the lack of traction up front can be overcome.
In some cases IFS is better off roading than the SFA, however these instances are few and far between.
I will not debate cases like the HUMVEE, or Baha racers, as there is little if any comparison between any of these vehicles and a standard IFS 4wd vehicle.
IFS is a costly suspension, in that there are many more components. By the same token it is inherently weaker due to the more components in its makeup.
A solid front axle is never going to provide as much comfort on the roadways as IFS. This is due to the makeup of the system. The newer Jeeps are more comfortable then thier predesesors due to the coil springs, and along with the coil springs comes greater articulation, however one must remember that with a solid front axle there is but one pivot point. As one front tire hits a pothole and moves down, the other tire must move up the same distance. Again this is limited by the components used in the suspension. Upper and lower control arms, anti-swaybar, the bumpstops and a few others. Of course lifting the vehicle will increase the distance it can travel, and disconnecting the anti-swaybar will allow even more articulation. For this reason the solid axle is a better suspension for most all-around offroad driving.
In an FSA suspension system there are less components. This adds up to less cost when repairing, replacing, and modifying.
For this reason the FSA suspension is more durable, and easier to work on.
The Jeep was produced for the civilian comunity as a "Go anywhere, Do anything vehicle". I believe this still holds true today.
This is the kind of vehicle I want, so it is therefore my opinion that the FSA is better than the IFS
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Old 12-18-2007, 10:59 PM
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Heh, the Jeep was produced for the military.

Not that I want to give my age away, but here is a great comparison. Years ago racing bikes off road I had a hard tail and a springer front end. A real butt buster. Then we go bikes with 2" suspension on the rear and 2 or 4 on the front. Took a little getting used to as we couldn't "feel" the ground. We all got used to them and found we could go faster and do more. Then the rinky dinks came out with their long susepension, 4 rear 7 front. I remember riding my 1st Bultaco, it was totally unnerving, fast, no real sense of power since you had to ride the pipe and it floated across the ground like a high powered cloud. WOW! did that ever take getting used to. Now we have all these off road bikes with miles of suspension, wicked handling and power up the KAZOO!

Point? Early bikes = solid axle, pluggers by todays standards. Late bikes fully IS with P O W E R!!! Yeah, costs a whole lot more but you get what you pay for. If we had IS Jeeps it would have to be bigger to handle the long radius arms and start approaching the early Humjob. Imagine what it would take to come up with new shocks and spring rates. It would take a few years to sort out all the issues.

That said, The Jeep is fine enough for me, I'm not racing it, at least I don't intend to off road. It'll keep my costs down, I'll have more options on changes, and I can go fishing in relative ease. But there are times when a guys go to do what a guys go to do, power up!
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