Rock Krawler Suspension coming Triangulated 4 link

[SierraBronco]

My guess is you’ll be fine…since I haven’t see anyone else mention it I would imagine most people have been fine.

Welp…

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[Mdsuits]

Welp…

I think I finally got mine functional with the smaller shaft from Adam’s, the rock jock sway bar and trimming the skid plate….if I knew before hand what I know now I would have skipped the rk 4 link and ran what I had for this summer and over the winter done the Apg rear setup to match my Apg front.

 

[mpeugeot]

Welp…

Just needs a little duct tape and it'll be fine... Once it finishes self-clearancing.

 

[mpeugeot]

Ok I wanted to make people aware of something I haven’t seen brought up yet about RK’s 4 link……because of its ability to flex and the super short arms you do start to get some rear steer from the rear axle….which would not be a huge deal but the pinion yoke and driveshaft can contact the gas tank….RK is aware of the issue and suggested the smaller Adam’s driveshaft/yoke set up, rock jock sway bar and trimming the oem gas tank skid….i had planned on these upgrades anyway but this will definitely speed up the timeline….for what it’s worth it does drive amazing down the road. Definitely a huge improvement there.

Seems like I remember someone predicting something like this...

@Pressurized I spent 10 years doing 4 link design for bagged trucks. I did half ass shit to clear fuel tanks, compressors and cross members. I can straight up tell you that triangulating just the uppers links makes for some rear steer and coil binding/torn bags. When you cut corners to make it bolt on you get some draw backs.

Rock Krawler needs to prove the system. Just because it works on a jeep doesn't mean it works with ford. As far as I can tell they designed it, stuck it on their in house bronco and passed it out to a few insiders. Exodus installed the first publicly photoed one 2 weeks ago? We are looking at a very limited test base of bias people who I don't trust.

I need new rear links and want this 4 link. I don't want to be the idiot who has to weld new factory mounts on because of a janky design not working.

 

[Mdsuits]

Seems like I remember someone predicting something like this...

Yup. I remember reading this….basically the links are all too short for the amount of travel causing the axle to steer and move side to side quite a bit when it is twisted up…there are marginal gains in ride quality and flex but I don’t think it was worth the hassle, cost and extra stuff to make it work. I don’t see me keeping it long term but it is on there for the foreseeable future….

 

[Muffin Top]

because of its ability to flex and the super short arms you do start to get some rear steer from the rear axle….which would not be a huge deal but the pinion yoke and driveshaft can contact the gas tank….RK is aware of the issue and suggested the smaller Adam’s driveshaft/yoke set up, rock jock sway bar and trimming the oem gas tank skid….

for what it’s worth it does drive amazing down the road. Definitely a huge improvement there.

So the rear steer is just when flexing off-road? It's better than stock on the road? That's something.

 

[Mdsuits]

So the rear steer is just when flexing off-road? It's better than stock on the road? That's something.

Yes it is better on the road…but I believe with a good track bar bracket and an adjustable track bar you could get the stock 5 link almost as good…it definitely has good aspects, but it has flaws as well.

 

[mjp2]

Welp…

I thought I was baller running on-board air tools until you come rolling up with an on-board lathe.

 

[SierraBronco]

I thought I was baller running on-board air tools until you come rolling up with an on-board lathe.

Slowly saves weight too

 

[87-Z28]

.basically the links are all too short for the amount of travel causing the axle to steer and move side to side quite a bit when it is twisted up…there are marginal gains in ride quality and flex but I don’t think it was worth the hassle, cost and extra stuff to make it work.

When panhard bar is level with centered axle, max lateral motion is less than 1.5” for oem 5 link. (44” bar with <12 shock disp gives 15 max deg axle rotation and about 1.7” lateral motion). Less than 0.5” lateral motion for 6” of shock articulation. Very minimal affects for 5 link under most conditions. Panhard bar must be level.

5 link forces axle lateral motion to sweep along panhard bar frame hard point (pivot). 4 link can also result in out of plane motion that is not purely up and down. These motions are now dictated by the arc swept from the shortest links (usually the uppers). The shorter the link the greater the out of plane motion for the same given amount of axle rotation. Infinitely long links result in perfect up and down axle translation.

4 link definitely can have advantages but needs significant design considerations. Using factory hard points (mounts) may over constrain the 4 link design. Ties the design into predetermined link lengths and mount load capacity. Neither of which may be optimal.

Not at all saying this design is not good or 4 link is a bad idea. Quite the opposite. Just needs careful design considerations. the jury is still out on this 4 link design.

there are marginal gains in ride quality and flex but I don’t think it was worth the hassle,

I would love to see some real world data on the increased amount of articulation by the rear axle when going from oem 5 link to this 4 link. It is hard for me to imagine a significant improvement if 5 link panhard is level at ride height and flexible Johnny joints are on all links. I do think the 4 link may be better, just how much and is it worth the effort.

 

[Valhalla]

Leaf spring the rear...

 

[Arokcrwlr]

There are definitely drawbacks to this design - we really need longer arms and different mount points. I have discovered all of these issues myself. I am hitting the gas tank skid and just kissing the exhaust. I'm not going to worry about the exhaust for now. For skid clearance, I am putting on an Adam's DS this week...hopefully it will address most of those clearance issues.

I will say that I do see a huge improvement on road. I was using a RJ track bar and relo bracket before and my track bar was level, but I was still experiencing bump steer. I have no bump steer on road with this 4-link. Where it was down right scary was when panic braking - really had to concentrate to keep it out of the ditch. If budget allowed I would definitely go with the APG solution.

 

[Valhalla]

I see you guys talking about bump steer. I have zero on my 23 badlands. My suspension is not modified. I Run a body lift to fit 37's. Did you guys have bump steer before modification of the suspension?

 

[SierraBronco]

I see you guys talking about bump steer. I have zero on my 23 badlands. My suspension is not modified. I Run a body lift to fit 37's. Did you guys have bump steer before modification of the suspension?

I never noticed it on our more door bronco with stock suspension. Definitely had it on two of my older raptors

 

[Arokcrwlr]

I see you guys talking about bump steer. I have zero on my 23 badlands. My suspension is not modified. I Run a body lift to fit 37's. Did you guys have bump steer before modification of the suspension?

Yes, if I hit a railroad crossing at speed - not catching air but enough where the suspension would unload and came down compressing the suspension. Also, panic braking the front end would dive and get kind of squirrelly. Example - on the way to work one morning, doing about 60mph, I came around a turn in the road to find a bus broke down in the middle of the road - slammed the brake and almost ended up in a ditch.

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