Bronco engineered to beat Wrangler's VCI (traversing soft terrain) according to member on Wranglerforums

[Nickp]

Found this post extremely interesting in regards to solid axle vs. IFS, and where Ford is coming from with their design. I’m by no means a suspension expert and had never even heard of VCI, but Erik Latranyi who wrote the posts said I was welcome to share his posts over here. Thanks to him and should be a good discussion!

I was just chatting with the former Jeep suspension engineer who consulted on the Bronco and Bronco Sport.

Ford stayed out of the way and let the engineers do their job. The Bronco Badlands VCI is better than a Wrangler.

VCI is Vehicle Cone Index....an engineering term created by the US military and used to quantify how well a vehicle is able to traverse soft terrain (mud, soft soil, sand, loose rock, snow, loose dirt).

The primary driver of a good VCI is tires, of course. Just as we see the difference in using All-Season tires to Snow Rated tires on any vehicle. The secondary driver is the suspension's ability to keep the tires in contact with the ground, and with the proper downward pressure on each tire so the tire treads can do their job. The third driver is the ability of the AWD/4WD system to provide power equally. Lockers came as a result of discovering mechanical 4WD alone was insufficient for a high VCI.

Jeep designers always used VCI as a check of their work. Until the Daimler era, every Jeep needed to be able to traverse the Rubicon Trail without assistance of a tow strap. VCI was one means of predicting how well a vehicle could accomplish this. In fact, Chrysler scanned and then re-created a section of the Rubicon Trail at Auburn Hills, Michigan proving grounds so they could test vehicle capability in secret.

When Ford set out to make the Bronco family, it set the Wrangler as the benchmark to exceed. Ford knew the JK would be replaced and set its sights high. Ford executives got out of the way and set the Bronco engineers loose to do their job.

The result is that both the Bronco and Bronco Sport were set to exceed competitive Jeep models (Renegade/Compass & Wrangler). They accomplished that with the Bronco Sport and claim to have done it with the Wrangler. Proof will be comparison tests.

Those who cling to the solid axle vs independent suspension argument miss some important details. A solid axle setup can offer more articulation unless the independent suspension has long travel arms. If both offered the same amount of articulation, the independent suspension would yield a higher VCI than the solid axle because the independent suspension could keep more tires in contact with the ground and with more even pressure to the ground so they would actually work better.

At maximum articulation, Wrangler keeps all wheels planted, allowing them to work. This is an advantage at those extremes.

Rather than try to beat Wrangler at its maximum articulation, Bronco set out to beat Wrangler at 90% of its articulation range by ensuring all wheels had superior "grip" of the earth than Wrangler.

How?

The weakness of solid axles is that as they articulate, weight distribution at each tire changes. Independent suspensions can keep equal down-pressure over a wider range of articulation, allowing you to have more "grip". With solid axles, the tire with the potential for greatest "grip" might not have enough downward pressure to use that "grip".

Imagine a tire getting too much pressure on the ground. It takes more power to turn that tire. If the tire has too little pressure on the ground, it will spin the same as if it has low "grip". A properly designed independent suspension will articulate widely while ensuring all tires have similar downward pressure on the ground. Solid axles cannot do that.

This is why the Bronco will do better on loose dirt, rocks and terrain than the Wrangler....except for the most extreme situations that less than 1% of owners will ever attempt.

For those that modify, Wrangler will be better. But, from the factory, Bronco will be superior in all but a very narrow range of conditions....according to the engineers who designed it.

I hope this makes sense.

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[RyanP]

Found this post extremely interesting in regards to solid axle vs. IFS, and where Ford is coming from with their design. I’m by no means a suspension expert and had never even heard of VCI, but Erik Latranyi who wrote the posts said I was welcome to share his posts over here. Thanks to him and should be a good discussion!

Very interesting read. Thanks for posting.

 

[Gamecock]

That's really good insight. Thanks for posting.

 

[Raptor911]

I think this sums it up >> Those who cling to the solid axle vs independent suspension argument miss some important details. A solid axle setup can offer more articulation unless the independent suspension has long travel arms.

BTW .. Raptor has always had a massive LCA (aluminum) and UCA.

The Bronco also has a massive LCA (aluminum) and UCA (aluminum).

 

[lobbs611]

Good stuff

 

[Philly]

So what I got from this is that I need long travel arms. Good read!

 

[Nickp]

So what I got from this is that I need long travel arms. Good read!

The current Bronco probably would already be a “mid arm” setup to use Jeep terms. It’s not short arm... but it’s not quite long arm either. The warthog will probably be more of a true “long arm”.

 

[Toccoa]

So, IFS is better. Got it.

 

[Nickp]

So, IFS is better. Got it.

I haven’t used this in a MINUTE

 

[Lilj4425]

So it goes over rocks and through mud then?

 

[broncosor]

Nice read.
After riding offroad both in a Jeep Wrangler 2020 and a Bronco, what I am sure is that at high speed there is no comparison. The Bronco kills the Jeep.

 

[ZackDanger]

Recent quote from another thread that seems apropos:

[...]

What do I like most: This is tough, (I cant say everything lol) I guess my favorite thing is the suspension, as a chassis engineer I really appreciate the work that went into this. Its one thing to build a custom race rig, but to build something that can be mass produced cost effectively and hold its own this well at speed or on the rocks without compromising the "road manners" necessary to sell a modern vehicle is not an easy feat. [...]

What do I like least: As an engineer I know that there is more performance that could have been squeezed out of the suspension (IFS specifically, i'll give up on my dreams of OEM triangulated rear axle lol). (I have pursued a patent myself only to see Ford, specifically some engineers I know, had already published it) Maybe some of this is what's coming to the Warthog? We'll see, but it certainly could be applied to more than that. I can't slight Ford too much for not squeezing out more performance from the get go, after all you have to get a product out the door and cant develop a model forever. [...]

What surprised me the most: As I have said before, I have not worked directly on the Bronco, so some things I thought I "knew" were total misconceptions. Sasquatch package surprised me. And although I am not getting it (no reason on Badlands imo) I think it is brilliant. Through development I thought the larger Hoss equipped Broncos were the rumored "Warthog" and that the Warthog would be launched along side the normal Broncos as a "Raptor" variant. I was pleasantly surprised to see that these beefy Hoss boys were available across the board and were still not even what we were considering the "Warthog"

 

[Philly]

The current Bronco probably would already be a “mid arm” setup to use Jeep terms. It’s not short arm... but it’s not quite long arm either. The warthog will probably be more of a true “long arm”.

That would be nice! Realistically I won't need it, but I like the idea of pulling parts off an old Warthog later on or at least being able to order some parts tested and backed by Ford. I know aftermarket will be great, but because I know next to nothing about IFS, OEM support makes me warm and fuzzy inside.

 

[Newbie]

 

[vrewald14]

Love it. As an enginerd myself makes complete sense.

Fascinating background as well about benchmarking, military definition, Rubicon trail, etc...

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