rear stiffeners

Is there much benifit from running rear stiffeners? I see alot of builds with just the main stiffeners and sometimes the front. I already have staangs fab stiffeners on my jeep and I fab up a set of fronts like the tmr's. I was just debating if doing the rear was worth it

nobody has an opinion on rear stiffeners

Nope. Other than I getta get off my butt and install mine

Doesn't seem like its worth the effort?

RocDog makes some nice full length stiffeners, but im yet to find a wright up or anybody running them

Oil Town XJ said:

Doesn't seem like its worth the effort?

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my jeep is well used, had 300,oookm life onroad before it became my frankenstein monster and I've had 4 years beating time on it. The hd chassis stiffens made a huge differnce, hopin the rear stiffeners,well stiffen. I plan on fronts soon, then tie it all together with some tube. They certainly cant hurt!,especially if you can make/ install them youself for near free

From my experience, if you don't cover at least two planes with "stiffeners" then they're not really stiffening.

Sure for the front they do a pretty good job of helping to prevent cracks from steering/trackbar leverage, but I'd like to see some that wrap around underneath the rails for the front/rear.

MoparManiac said:

From my experience, if you don't cover at least two planes with "stiffeners" then they're not really stiffening.

Sure for the front they do a pretty good job of helping to prevent cracks from steering/trackbar leverage, but I'd like to see some that wrap around underneath the rails for the front/rear.

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Exactly. There is a difference between stiffeners that actually stiffen the chassis and reinforcement plates that help to avoid frame cracks. Both are needed.

As far as stiffening the rear, the whole chassis benefits from any stiffening that can be done. The main benefit of stiffening the chassis is to make it last longer and not eventually crack to pieces when used offroad regularly. Fixing frame and body cracks all over the place is a major PIA and efforts to avoid it should be taken by anyone modifying their vehicle. Doing something front to back is a good idea, if it can be done, since simply strenthening one area can cause more flexing in other areas. The main area of concern is between the control arm mounts and the spring hangers, since this is the area where suspension flex stress is centered, but the front springs and weight in the rear of the rig also exert forces on the chassis.

Richard, in your opinion, how does having long arms attached at the frame near the crossmember effect chassis flex? Would this require different bracing than a short arm setup? Thanks and sorry for the hijack.

jeeperjohn said:

Richard, in your opinion, how does having long arms attached at the frame near the crossmember effect chassis flex? Would this require different bracing than a short arm setup? Thanks and sorry for the hijack.

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It's probably hard to quantify how much stress actualy comes from the arms. If the short arms have poly or rubber bushings then the mounts can take a good amount of twisting stress which will get transfered to the frame and body. If the arms have heims or some form of johnny joint then there's not so much stress. As we know, the arms and joints don't move as much with the long arms, so less twisting stress on the mounts and frame, but again it depends on what type of joint is used on the arms. I think part of the strenghening is for the mounts, and part is for the frame and body.

I think reinforcing between the front and rear mounts is good, but reinforcing for the whole length of the chassis is much better. Some twisting force comes through the mounts, but also quite a bit comes from the springs both front and rear. It's been awhile since we've had a good discussion on frame cracks, partly because they aren't so prevelant anymore since we've learned and more people are doing frame reinforcement and even cages from the beginning of their builds. But really, the only way to sufficiently stiffen the chassis is with a cage, and then it should carry forward to the front bumper somehow. I went a long time without any cracks and I thought that was really cool, but then it all seemed to fatgue at the same time and I got cracks everywhere. I posted a couple times way back about all the places that I had cracks, it's a pretty long list.

MoparManiac said:

but I'd like to see some that wrap around underneath the rails for the front/rear.

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x999, are you listening sponsors?

I'm running the hd offroad stiffeners, and they seemed great the first 2 months, but most of the creaking is back, and the hatch pops again.

Whats the best way to make your own wrap around front and rear stiffeners?

I know someone with a full shop who would help me fab, and weld a set for cheap.

srmitchell said:

I'm running the hd offroad stiffeners, and they seemed great the first 2 months, but most of the creaking is back, and the hatch pops again.

Whats the best way to make your own wrap around front and rear stiffeners?

I know someone with a full shop who would help me fab, and weld a set for cheap.

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Fronts are pretty easy. I made a set, but with the several companies selling a set for fairly cheap, its a toss up to do it yourself vs buying them.
http://naxja.org/forum/showthread.php?t=970131&highlight=homemade+frame+stiffeners

Rears I have never done, but they seem even easier than the fronts. Only issue I could see is that "body mount" right in the wheel well. Maybe this summer I will build a set.

I dont see a notch in HD rearstiffeners for the body mount, are you suppose to grind it down

Keep in mind that there is a difference between reinforcing the frame to avoid frame cracks and adding rigidity to the entire chassis to avoid body and frame cracking. Structure adds rigidity, extra thickness just makes that particular section stronger. Structure means multiple angles and multiple pieces, like a cage, or frame stiffeners that have multiple angles. Plating a section of frame is just a thicker frame, running tubing along the outside of that same section adds structure. A lighter piece of tubing, or an angled section of lighter plate, will add more rigidity that a heavier piece of flat plate.

So, goatman...

What would be the best way to reinforce the rear section without a cage? I've got a good rear bumper, but maybe a really good gas tank skid would help?

I know that like asking how to get traction without good tires, but a cage is a huge undertaking, and many of us want to increase the longevity of our dd's.

The front is easier because of braces and bumpers, but the rear seems hard.

One thing you can do is strengthen the rear crossmember, which is horribly weak. Many people find cracks around nearly all of the 8 bumper mounting holes in that crossmember when bumpers are removed after awhile. It's pretty straight forward to add a plate to the inside of that crossmember channel which will add more strength to the bumper mounts and will act as sort of a shear plane to resist rear chassis flex, plus let the bumper do a better job of adding rigidity to the chassis. Bumpers should be mounted well down the bottom of the frame with some boxed tube and not just a little piece of flat plate. I think skid plates would flex too much to make much difference, but I guess a good hitch would add something.

Something else that I did that I haven't seen talked about in a long time is adding a section of sheetmetal plate to the bottom of the tailgate latch. On the earlier XJ's with fiberglass hatches the latch can actually rip out of the hatch. You can cut out a piece of thin plate and drill some holes and pop rivet it to the bottom of the hatch to add a good amount of strength to the latch.

Those are good ideas.

In reference to strengthening the rear crossmember, where would the plate go? I've done lots of work back there, and I know that the 8 bumper bolts are very close to the shackles.

Heres what mine looks like now. (Not to thread jack, this is good info)

Where did you get that Cash for Clunkers decal? I want one

Goatman said:

A lighter piece of tubing, or an angled section of lighter plate, will add more rigidity that a heavier piece of flat plate.

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x100000


Shape = Strength




Colin's (Moparmanic) has some flat plates on the outside of his front rails. After he just put his sexy new bumper from AJ on there, he had a nice little run in with a tree. Just behind the bumper mounts, the framerail and plates both folded up and crunched in. no welds broke, just some nice bent frame action:thumbup: plates on the bottom would have really helped.




All the middle stiffeners out there (HD offroad, TNT, ruffstuff, etc..) are nice setups that do a great job because they fit around the contour of the framerail; the top, that little side angle, and the bottom. I was excited when i learned HD was coming out with front and back stiffeners too, but bummed when i found out they were one plane only. the fronts i feel are real important to plate the bottoms, if itll see abuse go ahead and do the insides too (think SBS style). the rears could benefit from plates on the bottoms and reinforce/tie-in the front hanger mounts. the sheetmetal around the stock shackle mounts really needs some plating. plating the side and bottom and some shackle relocation mounts is the way to go to see advantages of rear plates.