How to stop unibody flex/torsion

[xcm]

Sooo, the cage didn't do anything as far as the hatch not closing when not on level ground. The creaks are still there. Pretty disappointed and pissed off.

(the bad part of bolt on cages)

Probably just gonna sell it.

(the good part of bolt on cages)

 

[kastein]

There are no diagonals going across the vehicle, so that isn't much of a surprise unfortunately.

 

[Desert4x4]

I too, thought that was horrible. When I installed my rock hard cage, I ripped out the carpet, bolted it all in, then cut the carpet so it would fit around the cage pillars. The whole thing is incredibly solid and I am really happy with it. Took a while to fit it. Especially with an overhead console.
I have HD off-road stiffeners, a rigid co front bumper, and a well tied in rear setup... The whole thing is way more stiff.

Does your tailgate bind up when you have a tire off the ground? Mine still does.

 

[Desert4x4]

There are no diagonals going across the vehicle, so that isn't much of a surprise unfortunately.

Yea. true. Putting diagonals across the back would take up too much room id think. I wonder if that harness bar that runs between the b pillars would do anything.

 

[Rod Knee]

Yea. true. Putting diagonals across the back would take up too much room id think. I wonder if that harness bar that runs between the b pillars would do anything.

I doubt the harness bar would help at all. As mentioned, you need triangulation. Just look at any bridge truss and you will see what a cage should look like.

 

[zachandandy]

The only way to eliminate unibody flex completely is to leave it parked on level ground. Plating and a full cage go a long way but it will still flex a bit.

 

[NCCherokee]

Yea. true. Putting diagonals across the back would take up too much room id think. I wonder if that harness bar that runs between the b pillars would do anything.

I'm not really familiar with this particular cage, but if it is similar to most bolt in cages, then it is essentially free floating around inside your unibody, with some pivot points on the floor. Triangulation will make the cage itself stronger, but isn't gonna do anything until you tie it into the unibody in more places, not just the floor. Look at EricXJ's build or pretty much any jeep speed or hybrid cage. They are welding the interior cage to the ABCD pillars wherever possible, and to/through the roof and to the gutters in some case.

All that weld makes the cage and the unibody one piece that moves together and resists movement together.

Right now you have a cage that may save your life in a roll over, but not your jeep. I wouldn't sell it just yet. I'd weld the connections and to the floor, the. Start figuring out triangulation you can add or pay someone to add later, and way you can weld it to the pillars. Unless its like a mile away from the pillars, then I would consider selling it.

 

[Boostwerks.com]

The only way to eliminate unibody flex completely is to leave it parked on level ground. Plating and a full cage go a long way but it will still flex a bit.

I wouldn't go that far. Have you seen a WRC spec cage? The only time they flex is when they crash. Properly engineered cages will prevent the chassis from flexing almost entirely.

Desert4x4, do you have any pictures of the underside where the cage bolts through? It uses backer plates no? Any inside pics?

 

[Desert4x4]

Yes it has plates on the underside of the floor. That way it sandwiches the floor between the foot and the plate. For the front feet, my awesome rock slyders from detours are in the way. So I drilled a hole and bolted the cage foot to the slider using washers as shims. Seems to work OK. I put the plate on top of the floor to lift the front hoop a little. It pushes down on the dash pretty far. I then used fender washers for the other two bolts on the front feet. I might call rock hard to see if I can get some more plates

 

[srmitchell]

Does your tailgate bind up when you have a tire off the ground? Mine still does.

I can't tell you the last time I needed to open my hatch with a tire off the ground. I also have long arms and a ton of travel, with no sway bars so I rarely lift a tire unless I am doing something extreme.

I will say this- Between the cage, the frame stiffeners, my rough country long arm crossmember, my rigidco front bumper held on with well over 20 bolts, and my rear bumper which is tied into my hitch out back for a total of 21 bolting locations, the body feel FAR more rigid than stock.

Yes, the cage crushed the dash a little, and it creaks. I cared for a while and then I remembered that the jeep is 13 years old and chasing creaks is insanity.

 

[Desert4x4]

So if you stack about 3 of those plates under the front hoop feet, it only pushes down on the dash on the left corner a little.

Overall, I like the cage. The front hoop could've fit better, but the rest of it seemed to fit very well, especially since I mounted the rear hoop about an inch to the driver's side to accommodate a speaker.

 

[jeeperjohn]

you ever seen pictures of rock hard cages that were used in rollovers? they dont fair to well

Do you have any links to share? I am interested in seeing how they fail. It would also be interesting to see a comparison of how they hold up compared to weld in types that have the same number of mount points.

 

[ktfung]

Need some mig welding unibody advices

Hi. with 0.23 solid wire what voltage setting and gas flow rate that you found successfully weld frame stiffeners to unibody without burn through ? Thanks

 

[clean4drxj]

There are no diagonals going across the vehicle, so that isn't much of a surprise unfortunately.

I think what ken means is there's absokuteky no trianglation in the rockhard cage what so ever, I've seen one inperson, they look great to someone that doesn't know a whole lot..

 

[Desert4x4]

I think what ken means is there's absokuteky no trianglation in the rockhard cage what so ever, I've seen one inperson, they look great to someone that doesn't know a whole lot..

If it had more triangulation you wouldn't have as much space inside though. Its a good comprimise

 

[kastein]

Not really, seeing as you wanted to stop flex/torsion and put in a roll cage that does almost nothing to stop that.

But hey, whatever floats your boat.

 

[ColoradoRaptor]

If you have to be told why mounting a cage over your carpet is stupid, I'm not sure what to say really. Here goes...

Would you build a house by building a foundation, putting a layer of old mattresses over the top of it, and then building the frame over that?

LOL...............:roflmao:

 

[Desert4x4]

Well I unbolted only one foot of the roll cage the other day and drove over a bump. It creaked about twice as much, so the cage definitely does do something.

I'm starting to think that all cherokees flex and probably always did at least a little. I rode in a friends cherokee and it definately creaks a lot too, and has stress cracks in the D-pillar.

Chevy C channel frames from the 80s definitely twist more that the Cherokee I'd say.

So, aside from building a very substantial frame and welding it to the car everywhere, I think stopping unibody flex is like hasta

Hate it or love it...... I guess

 

[Boostwerks.com]

Well I unbolted only one foot of the roll cage the other day and drove over a bump. It creaked about twice as much, so the cage definitely does do something.

I'm starting to think that all cherokees flex and probably always did at least a little. I rode in a friends cherokee and it definately creaks a lot too, and has stress cracks in the D-pillar.

Chevy C channel frames from the 80s definitely twist more that the Cherokee I'd say.

So, aside from building a very substantial frame and welding it to the car everywhere, I think stopping unibody flex is like hasta

Hate it or love it...... I guess

A unibody requires a well built cage to eliminate flex. The problem is that when you twist a unibody so many times, cracks WILL start to form. Period. Picture twisting a pop can over and over.

Frame railed vehicles are simply designed to twist evenly over the full length of the vehicle. The purpose of the body mounts being that they will absorb some of the twisting forces before transferring it to the cab/body.

There are drawbacks and benefits to both designs however. The unibody design is great for a low COG. However, it NEEDS to be reinforced if used offroad.

 

[blistovmhz]

I've got a question... Why do so many people seem to have this problem, but none of my 6 Jeeps ever have?
I've got no problem stuffing opposing wheels on a 6.5" lift. Even when the Jeep was stock (but with 6.5" lift) I've never had a problem with doors binding.
I beat the hell outta my Jeeps (to the point that most Jeepers try to talk some trail sense into me), and most of my Jeeps have been beaters.

My current rig is 6.5" long arm, 35's, wj knuckle (OTA/OKK), some decently built bumpers that both tie 2' into the frame rail, and I put a track bar mount brace in just cause, but I've just never had any symptoms of unibody flex.