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Research, bro!
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So, I'm having a full through dash cage built for my JKU. :bounce: DOM being order tomorrow and Jeep going under the scapel in about two weeks. I've had a PSC cage sitting in my garage for a while that I was going to modify to fit my goals, but decided to ditch that idea and go all in once I determined the vents/speakers could be saved.

Rig is not my DD, but driven multiple hours to get to trailhead as well as used to go on general camping/outdoor type trips, along with the occasional "damit, I just feel like driving the jeep" ride.

I'm going to to do frame tie-ins to the A- and B-pillars. What are your opinions/experience on the pros/cons or using bushings at the tie-ins - besides the obvious "it dampens the transfer of vibrations?" My understanding is a bushing creates a pivot, and hence weak point. ("Weak" being relative, but still there non-the-less.) Just how much more noticable are vibrations in a non-bushing design? Conversely, any idea how much "weaker' a bushing design is? ie the trade-offs.

I don't want to bring the suck to my road ride if not using a bushing design, but if those that have ridden in both say it's not much more suck, I might just go that route for additional strength. I haven't ridden in either to have any experience.
 

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About time your getting yours done...I know you have been racking your brain about pulling the trigger. Make sure your builder considers the fact of your windshield being attached to the cage when considering how you tie to the frame unless you like replacing windshield glass.
 

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The best design would be to cut holes in the floor/tub and run the tubing straight through to the frame and weld the tubes directly to the frame. This would still isolate the cage from the body and eliminate the vibes. You could use some CV boots or something similar to seal up the holes around the tubing. My YJ was built this way.

On my JK, I tied in the A and C pillars with control arm bushings, just cuz I had them in my garage. Still planning on doing the B, but at that point I will be re-routing all bars through the floor, directly to the frame like mentioned above... and eliminating the bushings all together.

Like control arms, the softer the bushing, the less vibration. But as you
mentioned, it creates a "squishy" spot in your cage design.

If you use bushings, it's important to pay attention the the direction in which the bushing will be loaded if you roll. :)
 

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Mine is welded to the body and tied into the frame via poly bushings. Even with bushings at the frame it has stiffened up the chassis quite a bit. It is enough that I can tell a difference driving it. I would be more worried about the frame or body fatiguing if you welded it all together.
 

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Mine is welded to the body and tied into the frame via poly bushings. Even with bushings at the frame it has stiffened up the chassis quite a bit. It is enough that I can tell a difference driving it. I would be more worried about the frame or body fatiguing if you welded it all together.
For sure. I wouldn't weld it all together(body/frame). But if you cut holes in the floor and run through the body(keeping the body isolated) you're good to go.:)
 

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The best design would be to cut holes in the floor/tub and run the tubing straight through to the frame and weld the tubes directly to the frame. This would still isolate the cage from the body and eliminate the vibes. You could use some CV boots or something similar to seal up the holes around the tubing. My YJ was built this way.

On my JK, I tied in the A and C pillars with control arm bushings, just cuz I had them in my garage. Still planning on doing the B, but at that point I will be re-routing all bars through the floor, directly to the frame like mentioned above... and eliminating the bushings all together.

Like control arms, the softer the bushing, the less vibration. But as you
mentioned, it creates a "squishy" spot in your cage design.

If you use bushings, it's important to pay attention the the direction in which the bushing will be loaded if you roll. :)

I'm probably missing something here, but you said the A and C are tied to the frame. Is then the B floating or tied to the body? Going cage to frame through holes in the body is strong, but I would not say its the "best way" if you still want to use the factory tops. The cage would float inside the body. Thats bad news if you plan on using the soft top, hard top, door surrounds, or tie to the windshield, because all those components connect to the CAGE AND BODY.
 

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For sure. I wouldn't weld it all together(body/frame). But if you cut holes in the floor and run through the body(keeping the body isolated) you're good to go.:)
I understand what you are saying. I'll probably do that when I take mine off the road for good since it won't have a windshield or top to worry about.
 

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The windshield has plenty of support without tying into the cage. Look at the Spyder JK's.
Yes, My B pillar bars are just into the body for now. A and C to the frame through plates in the body and bushings at the frame.
If the B is is to the body and the A and C are to the frame, that is alot of stress at the B pillar/body attachment point. Having no upper windshield support is fine for a trail rig, but is not even close for a long time DD or freeway traveling rig. Just measure the distance between your cage and windshield at a stop, then measure it at 75mph. Its readily apparent the winshield is flexing. Now factor wind gusts. All the reapeated stress and force is transferred to the lowest connection point which has the lowest leverage advantage for support. The "nutsert style" threads in the JK body begin to loosen up inside the sheet metal.
 

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Actually in a 2-door the b pillar lands right directly on top of a body mount. A simple sandwich plate and a few bolts makes it plenty strong.
My bad, I was basing my info on a 4door JKU which is what the OP is doing. The bodies are longer and the factory body mounts flex in a different direction and in a different porportion than Poly joints.
 

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if your cage is designed well and correctly your seats/belts will be attached to it an in essence a "capsule" should the bushing bolts ever shear.

Mind you we are talking severe levels of stupidity here :laughing: like barrel rolling it on the highway at 80mph.

Shearing a 5/8-3/4 bolt (no need to run a sleeve in the bushing, just a bigger bolt) takes some effort. Doing a isolated cage takes more time, cash and effort to make it just as strong and safe as a direct to frame mount.

Will you get less vibration.....maybe. you have to think about the durometer of a urethane bushing vrs the durometer of the factory rubber mounts. Not only are you mounting a "harder" bushing but you are mounting it out further than the factory mounts (less leverage) so pretty much your vibration is based on the hardness of the urethane mount as the factory ones are now moot.

But it is still less than steel on steel :D

I will mount mine on bushings in a nice double shear not necessarily for ride but more so for modularity. This way I can still pull the body off if need be as well
 

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CoLo4, I am giving my fab guy pics of your cage and stealing some of your ideas. Im not sure im going to use the bushing mount. I may just do a straight weld to the frame. Whats your thought.
 

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Research, bro!
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Discussion Starter · #18 ·
I'm probably missing something here, but you said the A and C are tied to the frame. Is then the B floating or tied to the body? Going cage to frame through holes in the body is strong, but I would not say its the "best way" if you still want to use the factory tops. The cage would float inside the body. Thats bad news if you plan on using the soft top, hard top, door surrounds, or tie to the windshield, because all those components connect to the CAGE AND BODY.
Excellent point. I am tying the the upper cage to the windshield and am thinking about fabbing up some sort of rubber isolator between the two to help mitigate cage and body movement variances there.

Going to sell the PSC cage?
Yea. Gonna wait until the it's done though, just to be sure no issues arise with the through-dash.

Having no upper windshield support is fine for a trail rig, but is not even close for a long time DD or freeway traveling rig. Just measure the distance between your cage and windshield at a stop, then measure it at 75mph. Its readily apparent the winshield is flexing. Now factor wind gusts. All the reapeated stress and force is transferred to the lowest connection point which has the lowest leverage advantage for support. The "nutsert style" threads in the JK body begin to loosen up inside the sheet metal.
Completely agree. About two weeks ago I drove in a newly installed PSC caged JK. Took it on the freeway and there was a lot wind buffereing at the windshield header. This was with the hardtop on too. That sealed the deal on connecting to the windshield for me.
 

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CoLo4, I am giving my fab guy pics of your cage and stealing some of your ideas. Im not sure im going to use the bushing mount. I may just do a straight weld to the frame. Whats your thought.
Just cut holes in the floor and go straight to the frame. No bushings necessary. As for the windshield header, you could tie that into the cage with bushings. :)
 

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RRauzer any update as to what you went with on your cage? I am looking to do the same on my two door and am looking for options.
 
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