The IFS vs SFA Thread

[FirstOnRaceDay]

here is one for the IFS guys. This is long, like almost an hour but it is the first lap of KOH which is all high speed and some rocks you could drive your KIA on, but if you watch in the whoop sections you can really see the body movement compared to the tire movement.

LFAO!
You will ROLL a Kia taking that “flat” section in a Kia.
Hence why the IFS guys were averaging a MUCH higher speed in that section.

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[OX1]

I've already put up a separate post of a killer IFS design, that at least maximizes clearance (doesn't help articulation,
but you can't have it all). From what spy shots I have seen, Ford is not putting out anything like it. So I'm not sure
what else there is to talk about.

My personal pet peeve with IFS is the stupid rubber boot covered CV's.
MANY times, having a rig that can literally blaze it's own trails without even being able to see
the terrain floor (server brush and/or hidden rocks and gully's with massive moss coverings, etc..),
I need to get into a situation, slightly off trail, to get to another wheeler that just
broke something and is in a pretty decent jam.

The number of heavy bushes to med size trees I've had wrapped around my suspension and poking
at my axles is in the 1000's. Is there some reason that Mercedes figured out in the 60's you don't need rubber booted
CV's on your knarly offroad rig, you can use an externally greasable, rebuildable, CV that you can literally drive into pointed rocks
or tree branches with it, over and over. I can't see how I wouldn't have ripped off a couple hundred CV boots over the years by now.

 

[BAUS67]

Portals. I'm hoping with all the hype with the Bronco the aftermarket will come along for the ride. these are avail for the Wrangler.

http://www.tibus-offroad.com/en/products/bolt-on-portals/jeep/

 

[BAUS67]

LFAO!
You will ROLL a Kia taking that “flat” section in a Kia.
Hence why the IFS guys were averaging a MUCH higher speed in that section.

I was just making a joke because someone in this forum posted video of a KIA on some slick rock and Cougar Buttes is tame compared to the true "rock" trails in Johnson valley.

 

[OX1]

Portals. I'm hoping with all the hype with the Bronco the aftermarket will come along for the ride. these are avail for the Wrangler.

http://www.tibus-offroad.com/en/products/bolt-on-portals/jeep/

Will an IFS be better at torque control than a std link SFA suspension? (rotational, "anti-torque" link "length" is shorter, but
there is technically 4 of them, guess it would depend on bushing dimensions/material the most, I'd guess)

I tore right through 1/2 inch plate on my front upper link after getting a bit of air under the front end.
Modified for a total of 3/4 plate on both sides (3/4 inch bolt) and it's been fine since.

 

[BAUS67]

Not up on the IFS stuff, it is pricey. But I look at it like the nature of the arm (being a triangle) it adds to its strength along with material/dimension.
as far as your link … that is why a lot of the aftermarket stuff is so beefy, the unsprung weight of 40" tires and live axle weight, the forces are incredible. That's why I was so surprised when I saw 35's on the Bronco because that means they had to engineer the suspension to handle it and with the next size being 37's it won't take much to get there. My 08 F150 when from 32's (stock) to 35's (leveled) and it seems to be taking it ok so far. So I'm sure they have done their homework so you won't rip the A-arms off because of the large tires weight. … See if they just would have given it a SFA won't have this problem. The biggest problem comes from trying to turn while all the pressure is on one side this is usually what snaps the axle. Going straight for the most part is not an issue. Crank the wheel, hit the gas and try to drive up that rock and SNAP, there goes the axle. Nice setup on 'ole blue there.

 

[TeocaliMG]

I may do another longer write up when I get the time but to be honest I don't think much has been brought up that we haven't discussed in detail already. One thing I would like to briefly touch on is the "less moving parts" fallacy. If you want to limit this to only the driveline, you are correct, but when you talk about total joints and links both set ups are darn near identical.

Excellent write up Jimmy, I would add though that not all wheel travel is created equal, when you analyze both the wheel path and torque from brakes and driveline, the front IFS travel inch per inch is far more valuable (as traditional travel). Every aspect of the wheel path can be contained and tuned for good performance in a variety of terrains. Long travel SFA on the front end is difficult to make with a useful axle path for anything other than rock crawling, where the alternative IFS does not care what its long travel is being used for. You are correct though that more travel can be achieved with SFA for the same track width, I am just contesting that you can achieve significantly more travel (on the front) that is useful, safe, and effective.

You touched on the leverage dynamic of SFA, but to be fair when both setups have disconnected sway bars they will achieve full articulation similarly easily. But yes obviously the SFA will have more at its limit.

To bring this around to my initial question though I want to keep these comparisons a little closer to stock because as I said, when we start talking about built rigs, you can do whatever you want. Whether that's SFA or IFS. (I have big plans for mine, as i'm sure you guys do as well) And I still stand by the position that the apparent off-road advantages of SFA over well designed IFS in stock or near stock form (like 37" tires or less) are overrated or misrepresented.

Thanks for the added input guys, I love talking about this and i'll add more when I get the chance. I will say that in general I like the offroad enthusiasm of the pro SFA guys!

 

[OX1]

Not up on the IFS stuff, it is pricey. But I look at it like the nature of the arm (being a triangle) it adds to its strength along with material/dimension.
as far as your link … that is why a lot of the aftermarket stuff is so beefy, the unsprung weight of 40" tires and live axle weight, the forces are incredible. That's why I was so surprised when I saw 35's on the Bronco because that means they had to engineer the suspension to handle it and with the next size being 37's it won't take much to get there. My 08 F150 when from 32's (stock) to 35's (leveled) and it seems to be taking it ok so far. So I'm sure they have done their homework so you won't rip the A-arms off because of the large tires weight. … See if they just would have given it a SFA won't have this problem. The biggest problem comes from trying to turn while all the pressure is on one side this is usually what snaps the axle. Going straight for the most part is not an issue. Crank the wheel, hit the gas and try to drive up that rock and SNAP, there goes the axle. Nice setup on 'ole blue there.

I guess I kind of find it funny that a 35 is some kind of holey grail now, when I've run 35's on my 79 (used mostly for plowing and towing 24' boat, but did wheel back in the day) for 17 years (with only upgrades being frame track bar mount to fix slightly egged holes after 14 years and 140K, and track bar urethane bushings). Several years ago I did upgrade to 3/4, 78/79 D44 stuff, but that really only upgrades brakes and one wheel bearing.

Also ran that stock rad arm suspension for many years on 800 lbs of 44 boggers. Yes, it was a D60 with grafted on rad arm mounts, but the arms, track bar, and drag link (maybe tie rods, forget if that was D60 stuff) was all stock stuff (modified for lift only).

Had run upwards of 38's on the front 44 and would have upgraded shafts (the only issue) if there were any to get back then.

Anyway, when you've had the ability to drop in an available stock axle, really easily, that can handle clutch dumps with a mild 514, 6.68 first gear, as mentioned 800 lbs of tire, on a rig well over 6000 lbs, you kind of become somewhat disheartened when your are told no one wants to do that anymore boomer, you need to get with the times.

PS, these not considered 36's anymore?
https://www.ntwonline.com/36x13-50r17e-irok-radial-interco-super-swamper-8979.html

 

[OX1]

You touched on the leverage dynamic of SFA, but to be fair, that is not the mechanism that enables more articulation, it just helps the setup which naturally has more articulation overcome its necessarily higher spring rates. IFS can be made with softer springs due to the naturally higher roll rate meaning that when both setups have disconnected sway bars they will achieve full articulation similarly easily. But yes obviously the SFA will have more at its limit.

Honestly, I don't care that much about the articulation, except for it's "righting" ability on the rare occasions I actually get to "crawl" on really
off camber, high traction situations. It's the inexpensive beef that you need when you are crashing through the terrain, with really momentum the only thing keeping you going. A good part of the time, you might not have any wheels on the ground. So unless you are going to always wheel easy trails near me, you are going to need to upgrade, as the trails have zero traction at almost all times, making what looks super easy, almost unpassable at "crawl" speeds.

And finally, can your IFS rig do this, on a REALLY bad day, IE steering arm, which bolts onto knuckle on 404 mogs, was loose (my bad for not checking tightness before that a trip), busted off, and was not even weldable back on (we tried). Tow 15,000 lbs of stuff out on the "main" trails? I was on hitch "rock spotter" duty riding the trailer. Being off camber on top of a deck over was lots of fun, LOL!!

Anyway, still no answer on why Ford didn't try to up the IFS game, by at least doing those high clearance lower arms?

 

[TeocaliMG]

Well to answer part of your question, losing one tie rod is not a severity ten, but losing the drag link is... DFMEA's are fun (not)

 

[OX1]

Well to answer part of your question, losing one tie rod is not a severity ten, but losing the drag link is... DFMEA's are fun (not)

Not sure what question you are answering, but I do consider losing even one tie rod end about as bad as it gets, if you are doing anything but crawling. In my case, I lost drag and tie rods in one shot when these bolts snapped. It was 11 years of abuse and I had forgotten that whoever I got the axles from, had used non factory, inferior bolts. First pic shows they were tight earlier in the day (unlike how I first remembered it as loose bolts).

orig style on right.

Anyway, that just brings up another point as to why I think many more people would take their new rig on even moderately
hard "crawling"/trail riding vs any high speed stuff. It's typically much safer for families (even if you roll), way less damage if
you lose suspension or steering pieces, slow so you can be guided if needed, can typically opt out of harder things with a
larger group.

 

[TeocaliMG]

Not sure what question you are answering, but I do consider losing even one tie rod end about as bad as it gets, if you are doing anything but crawling. In my case, I lost drag and tie rods in one shot when these bolts snapped. It was 11 years of abuse and I had forgotten that whoever I got the axles from, had used non factory, inferior bolts. First pic shows they were tight earlier in the day (unlike how I first remembered it as loose bolts).

orig style on right.

Anyway, that just brings up another point as to why I think many more people would take their new rig on even moderately
hard "crawling"/trail riding vs any high speed stuff. It's typically much safer for families (even if you roll), way less damage if
you lose suspension or steering pieces, slow so you can be guided if needed, can typically opt out of harder things with a
larger group.

I was just stating that in reference to the tie rod failure you experienced, Noting that both SFA and IFS have tie rods yet only the SFA has a draglink. Both SFA and IFS can limp away with tie rod failure, but I agree that is less than ideal.

Also I don't disagree that crawling is safer than desert running, but I am not stating the obvious there, I am more concerned with which architecture will make the best all around stock platform for offroading. And knowing that all of the SFA guys disagree with my premise there I am looking for reasons why that are apples to apples.

Jimmy made a good point about wheel travel to which I contest that IFS has higher quality wheel travel inch per inch as a do-all off roader.

And you made a good point that you don't always need to have aftermarket axles for very large tires, to which I would say that you generally should.

I emphasize apples to apples SFA vs IFS stock for a do-all offroader because when it comes to the aftermarket and modification to me it does not matter whether the Bronco has IFS or SFA. I would be gutting all of it and building something better than either. But until that project starts i'll take the long travel IFS as a jack of all trades. You SFA guys may have a different vision of a "jack of all trades" and that's fine, but I bring this up because the vast majority of offroaders will be better served overall with IFS (yes i'm talking offroad, not on road), and us "hardcore guys" will be replacing all the hardware anyway. Jeep/Bronco, IFS, SFA, doesn't matter. You'll be putting it on long arms and one tons, or like me you'll be putting in Ultra narrow diffs and 20+inch travel control arms.

So if i'll play devils advocate a bit:
A stock offering SFA may save you money on the steering gear since it would have RCB stock. (though you really should upgrade that too)
A Stock SFA will be slightly easier to fab up since you don't have to work around/modify the cradle (yea good point, that could be annoying)
Those are kinda the things i'm thinking for the "SFA or bust" crowd

To clarify my premise again:
If you are not "hardcore" enough to be going bigger than 37's or greater than 12" travel then you will be more than adequately served by proper IFS or SFA and being offered only one should not be a deal breaker.

If you are hardcore enough to be doing all the mods, why is IFS a deal breaker when you will be replacing or fabing just about everything? (like my examples)

Lastly, considering what disadvantages do exist in my second premise for the few % of us who will change everything, does that reasonably outweigh the significant advantages of IFS off-road in almost every arena but legit crawling? For the vast majority of enthusiasts? (yes actual enthusiasts not just daily drivers)

 

[JimmyDean]

I was just stating that in reference to the tie rod failure you experienced, Noting that both SFA and IFS have tie rods yet only the SFA has a draglink. Both SFA and IFS can limp away with tie rod failure, but I agree that is less than ideal.

Also I don't disagree that crawling is safer than desert running, but I am not stating the obvious there, I am more concerned with which architecture will make the best all around stock platform for offroading. And knowing that all of the SFA guys disagree with my premise there I am looking for reasons why that are apples to apples.

Jimmy made a good point about wheel travel to which I contest that IFS has higher quality wheel travel inch per inch as a do-all off roader.

And you made a good point that you don't always need to have aftermarket axles for very large tires, to which I would say that you generally should.

I emphasize apples to apples SFA vs IFS stock for a do-all offroader because when it comes to the aftermarket and modification to me it does not matter whether the Bronco has IFS or SFA. I would be gutting all of it and building something better than either. But until that project starts i'll take the long travel IFS as a jack of all trades. You SFA guys may have a different vision of a "jack of all trades" and that's fine, but I bring this up because the vast majority of offroaders will be better served overall with IFS (yes i'm talking offroad, not on road), and us "hardcore guys" will be replacing all the hardware anyway. Jeep/Bronco, IFS, SFA, doesn't matter. You'll be putting it on long arms and one tons, or like me you'll be putting in Ultra narrow diffs and 20+inch travel control arms.

So if i'll play devils advocate a bit:
A stock offering SFA may save you money on the steering gear since it would have RCB stock. (though you really should upgrade that too)
A Stock SFA will be slightly easier to fab up since you don't have to work around/modify the cradle (yea good point, that could be annoying)
Those are kinda the things i'm thinking for the "SFA or bust" crowd

To clarify my premise again:
If you are not "hardcore" enough to be going bigger than 37's or greater than 12" travel then you will be more than adequately served by proper IFS or SFA and being offered only one should not be a deal breaker.

If you are hardcore enough to be doing all the mods, why is IFS a deal breaker when you will be replacing or fabing just about everything? (like my examples)

Lastly, considering what disadvantages do exist in my second premise for the few % of us who will change everything, does that reasonably outweigh the significant advantages of IFS off-road in almost every arena but legit crawling? For the vast majority of enthusiasts? (yes actual enthusiasts not just daily drivers)

If you’re changing everything shouldn’t you want the option with the lowest up front costs?

 

[TeocaliMG]

Also OX1, if I may ask, why are you considering a Bronco over say a Superduty Tremor? Other than the fact that the Bronco is just plain cool, and probably cheaper than a good spec Tremor. If you aren't into the articulation as much as the huge tires the Superduty offers quite literally a super-duty driveline/steering/chassis. Spec it with the powerstroke and you can spin those swampers through anything you want!

 

[TeocaliMG]

If you’re changing everything shouldn’t you want the option with the lowest up front costs?

Yes, see there's a good point! I have no way to prove or quantify that. Its no secret that doing slight upgrades to SFA is cheap but from the OEM perspective I am not convinced (from what I have seen and worked on) that SFA is a big cost save offered stock. But again, I have no hard data to compare there, i'm sure the bean counters know.

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