Excellent IFS vs SFA Article -- 2021 Bronco's Advantages In Having Independent Front Suspension

[Hammerheadfistpunch]

Yeah, I don’t really get the concept of this RTI formula and the resulting number (higher is better) conveying capability, at least in certain situations. The Longer wheelbase will go up the ramp further. Maybe I’m missing something. I was actually referring to suspension travel/flex.

By “flex balance” I’m guessing you’re referring to counterweight/transition speed of weight transfer? IE, teetering on rocks and drops/rises would be more aggressive in a short wheelbase.

Sorry, I did a really bad job explaining it. RTI is ramp travel index. The ramp travel is the obvious part - i.e. you drive a single tire up a ramp, usually 20 degrees until the opposite side rear tire is in free air - and the index is a way to convert the distance traveled up the ramp into a usable metric of comparison. The formula for a 20 degree ramp is RTI = (distance / wheelbase) x 1000. The 1000 is there just to turn the ratio into an impressive sounding number. The important thing here for our discussion is the wheelbase issue.

the longer the wheelbase the less affected the rear axle is affected by the steep climb on the front axle. short wheelbase will require the rear axle to articulate further faster. That's what's meant by longer up the ramp. you could take a school bus to the top of a 20 degree ramp before the rear tire found free air. conversely, a short wheelbase will activate the rear axle far sooner and more extreme. That's why the wheelbase is considered, so vehicles of different wheelbases can be compared accurately (or accurate enough).

Flex balance is the amount of flex in the front compared to the rear. if the rear is very flexible but the front isn't than as the front wheel goes up the ramp its going to rely more on the rear axle to prevent a rear wheel lift. the longer the wheelbase the more the rear axle can play a role. Even if its not reflected in the actual number the actual distance up the ramp will almost always be further with a long wheelbase. i.e. the 4 door has a worse ramp score than the 2 door, but the 4 door will travel further up the ramp.

The Bronco has the same trouble as my land cruiser, where the rear is crazy flexible but the front is only so/so. In some situations thats enough, in others it leaves a little lacking.
here is a video showing what I mean. you can see how much harder the rear is working than the front. if the front was more balanced to the rear you would need less in the rear for the same effect

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[BAUS67]

RTI numbers share similarities to a chassis/engine dyno numbers in that, the two (or more) vehicles you are comparing need to be on the same ramp the same day to get quality comparable results.

I see it all the time, my car makes 750 wheel HP, yeah well mine makes 850 at the wheels. We have a dyno at our shop and I can tell you first hand I can make that number say anything you want, just change some parameters. It will also "load" the vehicle so hard you can break it ( the vehicle), same as an engine dyno. Has anyone ever hear/or saw 850HP at full song, 8500 RPM, then be pulled all the way down to 3000 RPM but still at full throttle ??? A dyno at one shop will not give the same readings of a dyno at another shop. So if person A (750HP) is in Timbuckto and person B(850HP) is at the north pole you will get different numbers. Put A at the north pole and he might make 875HP but you can compare that to B unless B is there the same day. Air quality has a factor on total HP. And so does the dyno.

sorry if this is confusing to some, but I wanted to show how when comparing one vehicle to another's RTI score it should be on the same ramp, just as a dyno comparison should be done on the same dyno, same day.

 

[Hammerheadfistpunch]

RTI numbers share similarities to a chassis/engine dyno in that, the two (or more) vehicles you are comparing need to be on the same ramp the same day to get quality comparable results.

I see it all the time, my car makes 750 wheel HP, yeah well mine makes 850 at the wheels. We have a dyno at our shop and I can tell you first hand I can make that number say anything you want, just change some parameters. It will also "load" the vehicle so hard you can break it ( the vehicle), same as an engine dyno. Has anyone ever hear/or saw 850HP at full song, 8500 RPM, then be pulled all the way down to 3000 RPM but still at full throttle ??? A dyno at one shop will not give the same readings of a dyno at another shop. So if person A (750HP) is in Timbuckto and person B(850HP) is at the north pole you will get different numbers. Put A at the north pole and he might make 875HP but you can compare that to B unless B is there the same day. Air quality has a factor on total HP. And so does the dyno.

sorry if this is confusing to some, but I wanted to show how when comparing one vehicle to another's RTI score it should be on the same ramp, just as a dyno comparison should be done on the same dyno, same day.

eh...I get what you are saying about a dyno but there are a TON of variable for power generation as well as power measurement. with a ramp its literally just a chunk of metal at the same uniform angle. so long as the ramps are close enough to the same angle its not going to make a bit of difference in the total score for comparison. tire pressure would have more effect than difference ramps.

 

[BAUS67]

Just curious what the RTI for this would be ????

/jk

 

[Jdc]

I am not saying you are making things up, but please explain to me specifically what makes the Bronco IFS better than an FJ Cruiser or Tacoma. I am genuinely curious since I haven't seen any information to indicate that it is.

I assume by "wheel package" you are talking about being able to run larger tires, correct? Sure, the factory offered tire sizes are great on the new Bronco, but the H3 had 285/75R16s (33") way back in 2006. Granted the Bronco is available with 315/70R17s (35") which is impressive, but somewhat tainted by the fact that Ford had to limit suspension travel to make it work, and they were seen rubbing in one of the Rubicon videos.

As for suspension travel, how do you figure the Bronco is so special? Stock travel is 7.87" for most models, and 9.45" for the Badlands. For reference, the Tacoma Baja had 9.25" (I can't find total numbers for the more recent TRD Pro models), and a ZR2 has 8.6". Truthfully though, I am surprised how weak the mid-size competition is, so maybe the Bronco is better than I initially thought. Still a far cry from the 13" of travel the Raptor has, and not that impressive for something only a few inches narrower than a typical full-size truck.

For reference, to highlight the shortcomings of the Bronco's SLA IFS vs. a center-mount differential IFS, The Polaris RZR Turbo S is only 72" wide (vs. ~76" for the Bronco) and has 19" of wheel travel. A Can-Am Maverick X3 is 72.8" wide and has 22" of wheel travel. I am not saying the Bronco should be anywhere near that, but I am trying to emphasize the limitation of the SLA IFS system and why it is not like the IFS you see on dedicated desert machines. I have ~13" of wheel travel on my 73.5" wide TTB rig with nothing more than some extended radius arms and ~$160 of springs and shocks. The factory arms are ridiculously short, and my extended arms are about the same length as the factory radius arms Ford used on their solid axle vehicles.

The 700 Ford published was for the 2 door Bronco. The 4 Door was specified at 620. The two door Wrangler similarly scores higher than the 4 door, but the numbers from FourWheeler were using a 30º ramp which results in lower scores, so they aren't comparable.



Stock for stock, certainly, a Bronco should hang with a Wrangler pretty well. The difference is that some very minor suspension work and a set of 35-37" tires (some armor too if you aren't a fan of the crushed beer can look), and a Wrangler Rubicon can handle pretty much any non-buggy trail and still be plenty comfortable on the road. The Bronco will take a lot more effort to do the same, and this is what I was hoping to be able to do with the new Bronco since I am a Ford guy and didn't want to be a part of the Jeep collective.



I'd be happy to let you see if you can follow me, mostly because I love wheeling and am always willing to be impressed. I know of many trails that have never been done by an IFS vehicle, much less an IRS one...

Given the back and forth here between you guys I feel like this is needed

 

[rak2]

Which axle would be best for going to get groceries?

Which axle would be best for avoiding warranty support arguments with the manufacturer?

 

[Bison]

Independent is better 95% of the time vs solid axel. I don’t need an engineer to tell me that.

Carnage canyon Buena Vista Colorado, Buggy trail. One of the hardest in the state, probably top 10 at least. Fj cruiser with bald 35’s did it. It was his 3rd time on that trail. Not one of our rigs made it out the exit without winching and the biggest tire was 42” Smallest was 39”. The Fj cruiser’s group caught up to us on the traiL and passed us. Another guy in his group had a Cherokee on bald 33’s. Minimum tire size for the trail is 37”. So I tend to not listen to anyone on the subject after that. Ifs can do anything your willing to do with it but it’s easier to do the harder stuff in a solid front axel.

 

[PDiddy]

Independent is better 95% of the time vs solid axel. I don’t need an engineer to tell me that.

Carnage canyon Buena Vista Colorado, Buggy trail. One of the hardest in the state, probably top 10 at least. Fj cruiser with bald 35’s did it. It was his 3rd time on that trail. Not one of our rigs made it out the exit without winching and the biggest tire was 42” Smallest was 39”. The Fj cruiser’s group caught up to us on the traiL and passed us. Another guy in his group had a Cherokee on bald 33’s. Minimum tire size for the trail is 37”. So I tend to not listen to anyone on the subject after that. Ifs can do anything your willing to do with it but it’s easier to do the harder stuff in a solid front axel.

So what it sounds like to me, is that we need to be wheeling on bald tires to get the best out of the vehicle.

All joking aside, the driver makes the biggest difference. I mountain bike all the time, but no matter what bike tech I have, I will never be able to do this.

 

[Bison]

Not much of finessing it through that trail unless you have 39’s.

 

[BroncoRevital]

First of all

But seriously this is great. I love all the discussions about this. This is truly what will differentiate the Bronco from Jeep. Well that and the more interior refinement.

To me the only real down side is the dependability factor.
If anyone wants to do extreme off-roading they are heavily modifying the suspensions anyway. In all other facets the IFS is the reasonable choice. I do wish the Bronco had a higher payload and maybe a SFA would help in that regard though.
If Ford made a SFA Bronco Id buy it but I’m not not going to buy it because it has IFS. I’m sure I’m actually going to enjoy it more most of the time because of the IFS so I’m not mad at it in the least.

This new renewed rivalry between Jeep and Bronco is really going to take this debate far and will be fun to see it play out.

Here’s an even better article on this subject

 

[Dads_bronze_bronco]

Not me! I'm more of a grip it and rip it kind of guy

I do agree that most wrangler owners drive pretty slow because they wobble all over the place. Large gusts of wind can also be a bit scary at highway speeds in the Jeeps. IFS is definitely going to make my commute better.

I have no idea what you are talking about. It never occurred to me to drive 10-20 under and I am not passing Jeeps driving that slow either.

And the primary reason for driving slower would be wind and tire noise. A soft top or topless Bronco on mud tires will have the same problem.

 

[Philly]

I have no idea what you are talking about. It never occurred to me to drive 10-20 under and I am not passing Jeeps driving that slow either.

And the primary reason for driving slower would be wind and tire noise. A soft top or topless Bronco on mud tires will have the same problem.

I apologize, I should have clarified I was talking specifically heavily modified wranglers on the highway and not necessarily all of them. Also, “pretty slow” here in Michigan is going the speed limit on the highway. I have cruised in my Jeep with soft doors, soft top, and 35’s about 80+mph during rush hour to keep up with traffic no problem, but if the weather gets nasty or the wind starts hammering me, you best believe I am slowing way down to 65-70. Some people’s suspensions are also junk so they get the death wobble, or they just lack the confidence to drive quickly because of the nature of a square vehicle with a high center of gravity and SFA.

SFA is perfectly capable and I actually would have preferred it in the Bronco. I am simply trying to stay positive and look forward to what IFS has to offer. Because of the nature of an IFS setup, it will almost definitely be smoother for on road driving and, like I said, this will make my commute more enjoyable.

My Bronco will be my daily driver and I expect it to be a lot of people’s here on the forum as well. For this, IFS will be just fine. I also don't know anyone who drives slower because their tires make to much noise... turn the music up!

 

[Dads_bronze_bronco]

I apologize, I should have clarified I was talking specifically heavily modified wranglers on the highway and not necessarily all of them. Also, “pretty slow” here in Michigan is going the speed limit on the highway. I have cruised in my Jeep with soft doors, soft top, and 35’s about 80+mph during rush hour to keep up with traffic no problem, but if the weather gets nasty or the wind starts hammering me, you best believe I am slowing way down to 65-70. Some people’s suspensions are also junk so they get the death wobble, or they just lack the confidence to drive quickly because of the nature of a square vehicle with a high center of gravity and SFA.

SFA is perfectly capable and I actually would have preferred it in the Bronco. I am simply trying to stay positive and look forward to what IFS has to offer. Because of the nature of an IFS setup, it will almost definitely be smoother for on road driving and, like I said, this will make my commute more enjoyable.

My Bronco will be my daily driver and I expect it to be a lot of people’s here on the forum as well. For this, IFS will be just fine. I also don't know anyone who drives slower because their tires make to much noise... turn the music up!

Agreed then, however, I think if you heavily modify a Bronco like say the Wayalife Jeeps are modified 4+” lift, 40’s etc., it might wander less or not develop death wobble, but you’ll still be driving slower due to noise, fuel mileage, tire vibrations, etc. We’re talking extreme capability trade off there.

And if choosing between Jeep and Bronco for daily driver - IFS is better, but the Jeep is not that bad. I would chose which best fits what you like for the money and go have fun.

 

[Philly]

Agreed then, however, I think if you heavily modify a Bronco like say the Wayalife Jeeps are modified 4+” lift, 40’s etc., it might wander less or not develop death wobble, but you’ll still be driving slower due to noise, fuel mileage, tire vibrations, etc. We’re talking extreme capability trade off there.

And if choosing between Jeep and Bronco for daily driver - IFS is better, but the Jeep is not that bad. I would chose which best fits what you like for the money and go have fun.

Sounds like we are on the same page

 

[ewitz]

IFS pros:
Better handling.
Better ride.
Not a Wrangler.

?

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