Is my JCR bumper going to rip off the back of my jeep?

So I am a bit worried about pulling with my rear JCR bumper.
I have been thinking and the way it is, I am putting all the force on the factory 8 bolts only.

Green is the force from a strap, blue is bolts, red is steel.


This is how the bumper attaches to the nut strip. I made my own so uses all of them. But same idea.



Am I just being paranoid? How hard would it be to make a sleeve to fit inside the rails?

The integrated nut strip is the typical way to support loads for the rear bumper. It should give you a long worry free life. Of course a inner rectangle tube down the unibody rail picking up the nutstrip holes would be better and can be done with some fab work.

This is an old thread with many contributors. Many of the pictures are gone but it should give you some an over view of what others have done.

http://www.naxja.org/forum/showthread.php?t=931945&highlight=rear+bumper

Mounting the way you show it should not be a problem for straight pulling using a trap. However, for carrying a tire back there or pulling a trailer additional reinforcing may be necessary.

whitexj98 said:

The integrated nut strip is the typical way to support loads for the rear bumper. It should give you a long worry free life. Of course a inner rectangle tube down the unibody rail picking up the nutstrip holes would be better and can be done with some fab work.

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I know the nutstrip is always great to use. But with how the nut strip is tied to the bumper, it's not really doing anything till the factory nuts pull out of the frame.

techno1154 said:

This is an old thread with many contributors. Many of the pictures are gone but it should give you some an over view of what others have done.

http://www.naxja.org/forum/showthread.php?t=931945&highlight=rear+bumper

Mounting the way you show it should not be a problem for straight pulling using a trap. However, for carrying a tire back there or pulling a trailer additional reinforcing may be necessary.

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That's a great thread, sucks some of the pictures I really wanted to see didn't work though.

So mounting with the factory bolts should be fine, I mean I am sure there are many people out there with the JCR bumper that don't do huge modifications to it and don't have it rip off.

But I am a little nervous about it.
I think I will use the 2x4, 3/16" tubing and feed it into the frame rail like that thread shows on a couple rigs.

Would be nice to see a JCR being pulled on, it's work I will do, but will be out wheeling a couple times before i get around to it.

I am on my second JCR rear bumper on my second XJ.

The first one was their first generation bumper that was held on with the factory 8 bolts and the tie in brackets you posted a picture of. I pulled on that thing hard like most 16-18 year olds do. I towed a trailer with 4 show cows in it and all the show equipment that goes along with that. I yanked many friends out of the mud etc. I was never worried about it ripping off or tearing up the factory bolt holes, mainly because I was young and didn't think about those things, but I didn't need to be because after 4 years of thrashing I sold the bumper as I parted out the XJ and there were no cracks or any other signs of damage.

That bumper is now on another member's XJ with the same results.

Now I have the brand new Adventure Tire Carrier. Along with the nutstrips and tie in brackets, it has a bracket that goes on the corner to reinforce it some more. I have only had it on for about a month or so, but I am not worried at all about it ripping off the back of my Jeep.

Also I don't think you are correct with your diagram about all the force being on the 8 bolts, but I'm not an engineer.

My first XJ had a homemade bumper/tire carrier that tied into all 8 bolts (but not as well as the JCR) and I had my ass dragged up and over obstacles and trails I never should have been with a strap on that bumper. IMHO, having a swingout carrier is worse for your truck that yanking on a tied in rear bumper.

iluv83vettes said:

Also I don't think you are correct with your diagram about all the force being on the 8 bolts, but I'm not an engineer.

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It's not. Without going into great detail, load will be translated to all mounting points. How that load gets distributed at the mounting points will determine if something rips out or fails. More mounting points and more bearing surface at those mounting points reduces the stress and potential for material failure.

xriide said:

Am I just being paranoid?

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Yes. And i have a feeling no matter what anyone says you are going to go on and on about it anyway (by your previous posts). A tow hitch for an XJ only uses the 8 bolts and i have never heard of anyone having a problem.

Jakobi said:

It's not. Without going into great detail, load will be translated to all mounting points. How that load gets distributed at the mounting points will determine if something rips out or fails. More mounting points and more bearing surface at those mounting points reduces the stress and potential for material failure.

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Hmm, doesn't make sense to me. If there is a slight upward I can see it pulling on all.
I was led to believe the stock bolts weren't very strong. But I can't find anyone that's ripped off the bumper despite being told it happens "all the time" from the local group. I had a guy not pull me out cause he said it'll just pull my bumper off.

josh9mile said:

Yes. And i have a feeling no matter what anyone says you are going to go on and on about it anyway (by your previous posts). A tow hitch for an XJ only uses the 8 bolts and i have never heard of anyone having a problem.

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The tow hitch uses the nut strip, which I've always read as the strongest part which is why my post was asking how to get the pull force there. I'm not sure why you have such a problem with me to have made that post, but I'd suggest maybe skip my threads if that's how you feel.

Thanks for the answers everyone. I'll probably still make modifications, but it'll wait till I plate the frame and fix my crooked welding of the bumper.

your understanding of physics needs help.

rockclimber said:

your understanding of physics needs help.

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The worst part is I have Physics 126 and 146 from UofA. It's been 10 years though.
I think with a straight pull like pictured, the top factory bolts would be taking 50%, the bottom factory bolts would take 25% and the nut strip would take 25%
With the pull coming from lower, almost all the force would be on the top bolts, and with a higher pull it would almost all be on the nut strip.

If I took the 8 factory bolts out and then pulled I would bend the bumper down till the eye of the shackle was in line with the nut strip.

I dunno. Wheeling with a 3/4 ton diesel today, and will certainly be getting stuck with spring breakup. I don't think it will go anywhere though.

josh9mile said:

A tow hitch for an XJ only uses the 8 bolts and i have never heard of anyone having a problem.

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The OEM tow hitch that is on my XJ uses 8 nut strip bolts and '0' bumper bolts. Aftermarket tow hitches that I have seen installed on the XJ also uses only the bolts in the nut strips and none of the bumper bolts. The bumper brackets are designed to carry the load on both the horizontal and the vertical plane i:e, they uses an angle iron to secure them to the body of the XJ using the bolts in the nut strip. Think about it, that is the only reason for the nut strip. Neither of the two XJ,s I have owned came from the factory with nut strips.

xriide said:

Hmm, doesn't make sense to me. If there is a slight upward I can see it pulling on all.

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Nothing against you but that's because you lack a fundamental knowledge of statics. It boils down to this, if it's all connected, then load is being transferred. Not necessarily equally but is is being transferred.

techno1154 said:

The OEM tow hitch that is on my XJ uses 8 nut strip bolts and '0' bumper bolts. Aftermarket tow hitches that I have seen installed on the XJ also uses only the bolts in the nut strips and none of the bumper bolts. The bumper brackets are designed to carry the load on both the horizontal and the vertical plane i:e, they uses an angle iron to secure them to the body of the XJ using the bolts in the nut strip. Think about it, that is the only reason for the nut strip. Neither of the two XJ,s I have owned came from the factory with nut strips.

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I should have clarified that I meant the nutstrip bolts, not the actual stock bumper bolt holes.