• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

STRUCTURAL STRENGTH/2 DOOR OR 4 DOOR XJ

J

JEEPTUBE

NAXJA Forum User
Location
citrus heights
WHAT IS STRUCTURALY STRONGER? THE 2 DOOR, OR 4 DOOR UNIBODY? MY FRIEND SAYS THE 2 DOOR IS. BUT I SAY THERE ARE MORE PILLARS IN THE 4 DOOR THAT KEEP IT FROM TWISTING AS MUCH. WITH HIS 2 DOOR HE WILL GET OUT ON THE TRAIL AND HAVE A HARD TIME SHUTTING HIS DOORS WHILE FLEXED OUT. WITH MINE I CAN OPEN AND CLOSE ALL 5 DOORS WHILE FLEXED OUT AND NOT HAVE ANY ISSUES. HMMMM.

COULD IT BE MY FRIENDS SHITTY LIFT SETUP BINDING ON ITS SELF?

I HAVE THE RUBICON LONGARMS ON MINE.

SMOOTH AS SILK.
 
Well i belive the 4 door would have more strength like you said, but the 2 door is also pretty strong too, i seen a guy roll a 2 door off of a 12 foot drop off and it rolled twice landing upside down (he took out a few large trees) but we just rolled it back over and drove it back up the bank all that broke was the front and left side rear windows, it did not cave the roof at all. But about the doors not closeing when flexed, my 97 4 door does that also its not just a 2 door thing.
 
you could shape mine like a pretzel right now.....now floor. I gained a whole new respect for the XJ unibody in taking mine apart, and I'm still taking it apart,and apart etc.
The number of spot welds is incredible. The floor pans are welded to the body, cross rails and various stiffeners along with the "frame" and it is all tied together. I would think the 4 dr. would be the stronger because of the pillars.
 
The torsional strength of a box (basic XJ body structure) depends on the integrity of each of the sides. The more you remove from one side or any combination of sides, the weaker it (the box) will become. With a larger hole being required to accomodate 4 doors, it should be the weaker of the two. It is doubtful that the added pillar will make up the difference. It adds column strength in a vertical direction which might help in a roll-over, but wouldn't add much torsional resistance to fight chassis flex.

Comparing an individual 4dr to another 2dr doesn't really resolve the question. Who is to say how each has been modified and what effect that would have. Who knows how many tiny cracks might be growing in one vs the onther, difference is weight, amount of flex, blah, blah, blah...
 
MaXJohnson said:
The torsional strength of a box (basic XJ body structure) depends on the integrity of each of the sides. The more you remove from one side or any combination of sides, the weaker it (the box) will become. With a larger hole being required to accomodate 4 doors, it should be the weaker of the two. It is doubtful that the added pillar will make up the difference. It adds column strength in a vertical direction which might help in a roll-over, but wouldn't add much torsional resistance to fight chassis flex.

Comparing an individual 4dr to another 2dr doesn't really resolve the question. Who is to say how each has been modified and what effect that would have. Who knows how many tiny cracks might be growing in one vs the onther, difference is weight, amount of flex, blah, blah, blah...
Click to expand...

Concur. The two-door should actually be somewhat stronger, because more of the vertical/horizontal elements are filled with permanent "shear panels" (Google it if you want to know more,) than the four-door.

Besides, I'm inclined to think that the 2-door has a C pillar as well (behind the doors...) it's just relocated slightly.

Also, I think it's worth noting that greater flex could also indicate a greater tolerance for abuse and stress/strain. While I haven't verified this experimentally, if the elastic limit of the steel panels aren't exceeded, it should flex and recover rather neatly. I'd think the four-door would be more likely to have its elastic limits exceeded because of the reduced permanent shear panel area, and that could result in deforming the unibody with less stress.

Granted, I'm not a mechanical engineer (yet...) but that's my take on it. If I'm wrong, please point out my error...

5-90
 
5-90....

The C-pillar technically is present in all cherokees as it would be the one right behind the 1/4 glass.

All things being equal, which they usually are not, the 2 door "b-pillar" right behind the door is not larger than the 4 door, but tied in, overall into the body better.

But yeah...I'm going with you and max on this one.
 
I didn't mean that the pillar itself would be larger, just that there would be a larger permanent shear panel filling in the space between the pillars.

Pillars are strength elements, while shear panels help to locate the pillars. Try this sometime - make a small wooden square frame, and try to distort it. Then, fill it in with a sheet of lightweight rigid something (light plywood, panelling, veneer will do in a pinch, just so it's fairly rigid) and try to distort the frame again.

That panel you nailed on is a "shear panel." In order to function as a shear panel, it much be rigid, rigidly attached, and fill in the space between the strength elements. A shear panel does not usually contribute directly to the strength of the design, but it enhances the strength of everything else.

The doors are not shear panels - they're not rigidly attached, and they're not permanenent elements. That's why I'm inclined to think the 2D will be stronger - because more area is filled in with shear panels than the 4D. Since a shear panel will also help with "bounce back," that's why the flexion in the 2D chassis may be greater, but it will also experience less permanent deformation.

5-90
 
12GaugeXJ said:
DUDE. CHEROKEES SUCK. THE WILL FOLD LIKE A TACO. GET A REAL FRAME. THATS ALL. AND YES, IM SHOUTHING. :D
Click to expand...
high school must be out for the summer ...
Jeepn_Idiot.jpg
 
Yea, Highschool was out about 3 years ago. And I didn't know you lived next door and thought I was sexy. Thanks for the complement asshat. :D Later on after that picture was taken, my head was between my womans thighs.
69.gif
 
You must log in or register to reply here.

Similar threads

WGxj
please delete
Replies
2
Views
135
DirtySouthXJ
D
XJones
Free - front doors for 4 door XJ
Replies
0
Views
1K
XJones
XJones
2
2 Door XJ Regulator Fix
Replies
1
Views
1K
Ronbo
Ronbo
A
1987 Jeep Cherokee 2 door with pop out window
Replies
4
Views
1K
AJ_learns_XJs
A
Goose_XJ88
(Possibly) 2 door doors and black interior pieces
Replies
0
Views
1K
Goose_XJ88
Goose_XJ88
Back
Top