body movement and frame mounted cages - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 17 Old 01-04-2019, 10:46 AM Thread Starter
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body movement and frame mounted cages

Hey y'all I have a genright cage for my jku, I've been told that mounting to the frame was a no-go as the body moves too much compared to the frame. I was wondering if there are stiffer body mounts that would allow less movement in the body and reduce rattling of the body and cage meeting? if anyone has any input I'd greatly appreciate it!
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post #2 of 17 Old 01-04-2019, 12:15 PM
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Originally Posted by Brady Phelan View Post
Hey y'all I have a genright cage for my jku, I've been told that mounting to the frame was a no-go as the body moves too much compared to the frame. I was wondering if there are stiffer body mounts that would allow less movement in the body and reduce rattling of the body and cage meeting? if anyone has any input I'd greatly appreciate it!
Who told you it was a no-go?

Generally cages are mounted to the frame through bushings too.

Energy suspension makes a body mount kit that uses stiffer bushings.

Once you've added cage mounts (bushed) to the frame your body movement will be roughly nill.


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post #3 of 17 Old 01-04-2019, 12:22 PM
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This thread has my two favorite topics.
Genright cages and bush
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post #4 of 17 Old 01-04-2019, 04:14 PM
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This thread has my two favorite topics.
Genright cages and bush
Does GAR fall into the latter category? What about bacon, guns, and beer?

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post #5 of 17 Old 01-04-2019, 06:18 PM
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post #6 of 17 Old 01-04-2019, 07:27 PM
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Once you've added cage mounts (bushed) to the frame your body movement will be roughly nill.
I don't know a whole lot about cage design, but if you have independent body and cage mounts, wouldn't you typically keep the cage fully isolated from the body throughout leaving the body-movement unchanged? Or do you tie the cage directly into the body (and if so why?)
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post #7 of 17 Old 01-04-2019, 09:08 PM
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To have the cage truely isolated from the body it would have to be an exo cage or have big holes cut in the body where the cage goes through it. Most cages only tie to the body out of simplicity. I would think that the thing to do would be to sandwich the floor between your cage frame mount, and the cage that is inside the tub. Have some feet to spread the load and give you places to bolt the cage pieces together through the tub.

*edit* while having some bushings right at the frame.

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post #8 of 17 Old 01-05-2019, 01:13 AM
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Originally Posted by christensent View Post
I don't know a whole lot about cage design, but if you have independent body and cage mounts, wouldn't you typically keep the cage fully isolated from the body throughout leaving the body-movement unchanged? Or do you tie the cage directly into the body (and if so why?)
That's actually a difficult question to answer if you're getting technical. Most accurate answer would be....it depends. Lots of things come in to play.

Having the body and cage completely isolated (and free to move in different directions independently ) from each other CAN have some very bad consequences. Seat and harness not both bolted to the same thing would be an example.

Adding frame tie-ins with a cage welded (or bolted) to the tub is no different than adding more body mounts to the tub. It's the same thing. Even with exactly the same durometer bushings for the cage and body mounts, doubling the number of mounts will effectively cut body movement in half.

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post #9 of 17 Old 01-05-2019, 08:59 AM
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A lot depends on the vehicle. On the JK it takes a tremendous amount of work and time to do a truly isolated cage that has strength and that is due to the A pillar. The rear sections are pretty easy to do. The JK A pillar is pretty strong and does a great job of protecting in a roll over. Older jeeps like the TJ and Cjs had almost no strength in the body section below the windshield frame. This is why cages are generally connected to the windshield frame at the top. Since you connect there you need to use bushing tie ins everywhere else or risk breaking the windshield when the body flexes and it really does flex a lot on my 2 door and bet it is way more on a 4 door.

If you were not to connect to the windshield and wanted something that was going to protect you, you would need to remove the dash so you could not only do the A pillar but have a second lower dash cross bar and cage up thru the center of the console to the top of the windshield. Some triangulation in this area as well. In addition you want the cage to extend into and around the engine compartment. If you want to look at good cage design just finds some ultra 44 chassis to look at and see how the upper section is constructed.

Many people think they need a cage when they don't as the JK does a good job with its cage that was designed and crash tested to protect. No after market cage that I know of has any kind of actual testing or evidence of adding any protection over the factory design. These after market cages and bolt in sections can also be more prone to cause injury in an actual crash or roll over. People are eager to add a hard steel structure to their jeep but often don't take into account things like head and body clearance to the tubes and almost nobody adds proper padding to the tubes in areas of their heads. You will find cages are designed around fitting the top on the jeep and not sized for the occupants. Good seats and proper restrains is very important here as the factory belts will allow the occupants to move around too much where they may come into contact with cage.

I would say for most people a cage is not necessary and you are just wasting your money on a custom cage or bolt on additions if you are not going to run the trails that warrant them and if that is what you are running a properly built buggy will be a better rig and offer you more safety at a lower price point. When you get down to it there is no actual evidence that an aftermarket cage is going to protect you any better then the factory designed and tested envelope.
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post #10 of 17 Old 01-05-2019, 11:31 AM
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@thedirtman , I have to clarify one thing you said. And, lots of folks tend to get this wrong. There is no roll over testing that factory vehicles go through. None.

The two agencies that do crash testing are the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS).

The NHTSA gives a roll over rating. Here's how that plays out. It has exactly zero to do with how the cage performs.
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Finally, NHTSA's last test is a rollover rating. Interestingly, this isn't a test at all but rather a mathematical formula that takes into account a car's width and center of gravity. While NHTSA doesn't actually test vehicles for rollover risk, the agency maintains that this test is valid after comparisons with statistics from actual car crashes.
The IIHS has what they call a roof strength test.
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There's a roof-strength test, where a metal plate is pushed against a car's roof to determine whether it would easily collapse in a rollover.
The roof test is static. The plate is pushed straight down (slowly) on the roof until the vehicles weight is sitting on the roof.

To be fair, getting good data rolling vehicles is impossible. You'll never get a vehicle to roll the same way twice in a dynamic test. To say Jeeps have been tested for it is incorrect.

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post #11 of 17 Old 01-05-2019, 12:31 PM
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I think dirtman's is sage advice.
I still want one. Will probably get it sprayed with rhinestone encrusted bedliner.
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post #12 of 17 Old 01-05-2019, 02:13 PM
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In a Jk most of would experience a slow rollover. With a factory roll bar the front is supported by the windshield frame only. Wouldn't it be greatly beneficial to tie that portion into the floor like poison spyder offers?

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post #13 of 17 Old 01-05-2019, 02:35 PM
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not really since it has almost no side to side support.

and thanks for the clarification Kevin, but still the rops are designed for protection from the factory. I can't see them putting out a vehicle with a soft top that has not addressed roll over strength of the ROPS.

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post #14 of 17 Old 01-05-2019, 03:03 PM
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Originally Posted by thedirtman View Post
not really since it has almost no side to side support.

and thanks for the clarification Kevin, but still the rops are designed for protection from the factory. I can't see them putting out a vehicle with a soft top that has not addressed roll over strength of the ROPS.
There's no doubt the factory cage can hold the weight of the Jeep. Passing the IIHS's test proves that. You make a good point, I wonder if they deal with convertibles differently.

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post #15 of 17 Old 01-05-2019, 07:49 PM
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Originally Posted by gt1guy View Post
There's no doubt the factory cage can hold the weight of the Jeep. Passing the IIHS's test proves that. You make a good point, I wonder if they deal with convertibles differently.
Apparently a roll "cage" system pops up out of nowhere (usually the rear head-rests eject and are replaced by a steel bar) when a convertible detects it is about to roll over. I had no idea those cars did this!
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post #16 of 17 Old 01-06-2019, 08:44 AM
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My Audi A4 convertible has that system and a crazy strong windshield.

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post #17 of 17 Old 01-06-2019, 11:17 AM
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Quote:
Originally Posted by christensent View Post
Apparently a roll "cage" system pops up out of nowhere (usually the rear head-rests eject and are replaced by a steel bar) when a convertible detects it is about to roll over. I had no idea those cars did this!
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My Audi A4 convertible has that system and a crazy strong windshield.
Then I guess that's what the IIHS would be testing against.

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