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Rear shock hoop

damo252

NAXJA Forum User
Location
Roxborough, CO
I have been wanting better flex from the rear of the XJ. I ripped off a rear shock mount, so I have to fix it anyway, and have been thinking about a rear shock hoop.

I have seen the cross enterprizes one, but was wondering if there are any other ones out there?

And do they really allow more flex? (I really don't know if my shock limit flex or not :dunno: )
 
bigwhitey said:
Take it off, flext it and find out.
Ditto.
If you haven't raised your axle mounts, now would be a good time to do so.
That would allow you to run a shorter shock.
 
damo252 said:
Why would I want to run a shorter shock?

Isn't the point to run a longer shock so that they don't limit compression or droop of the springs?
You may need to adjust your bumpstops accordingly, to avoid bottoming, if at all.
If you raise your axle mounts 3" you will have 3" more extension, but 3" less compression, which may not be a factor.
It wasn't a factor on mine.
 
couple of issues. Yes I have made a shock-hoop that doubled as a rear stiffening cross member.
The stock upper shock mount is the highest and furthest mounting point away from the axle mount. this allows you to run the maximum length possible for a given application. Relocation with have some sort of negative effect on the shocks ability to dampen.
To make up for the shock length you have to move the upper mount inboard further. and the more angle you mount a shock from the direction of wheel travel, the less it dampens. example, if a shock is mounted straight up and down. then the shock 100% effective. if a shock is mounted at a 30 deg angle to the travel of the suspension arc of movement then you have only 75% effectiveness of shock dampening. 45 deg and your shock is only 50% effective.
But.... a shock hoop can be engineered to utilize 2 shocks per side. and if you've raised your lower mounts then you can still use a shock with a decent size of travel range.
 
I use an 8" travel shock mounted to the factory upper mounts and as far out board as I can go on top of the axle. I use every bit of it's travel, and need no more.

JKSshockmounts.JPG
 
Alright I see what you are saying about decreasing the shock length now.

What about bar pin eliminators, is that a good way to decrease the shock length?
 
no offense but you don't have rocks in Florida like we do in the west or even a little further north of you. but if you wanted to Whitey, you could make newer mounts for the tubes and gain probably another 2-3" of shock length on the axle tube. If your mounts were on the bottom edge of the tube and they stradled the ubolt some...
BPE's I consider a temp solution because it cuts about 1/2" to 1" off the upper mount. They call them bar pin eliminators but its still a bar pin and its still fastened in a similar fasion to a stock spring. a few years ago BPE's were a good solution at offering up more shock options because many shock MFG's didn't make every shock with a bar pin option. same goes for those goofy front upper stud style shock mount converter thingy's that let you use the more common eye to eye shocks that were more redily available vs the stock style of bar pin bottom and stud top.
But even bilstein 5150's can be supplied with the stud mount and bar pin type bottoms. same goes for RE monotubes. They come in all flavors and styles.
If you want to raise your lower mounts then something has gotta give. either moving the uppers inboard and doubleing up or putting the uppers through the floor, or some other means of keeping travel.
 
BPE's'll move 'em, what, an inch?.

This is mine with stock upper mounts and raised axle mounts and 12" shocks.

is.php

Would bottom out, on high speed whoops.


Here it is now, with the same shocks, but with a shock hoop.

is.php

Not bottoming out, now and I still don't run out of length.
 
Rawbrown said:
To make up for the shock length you have to move the upper mount inboard further. and the more angle you mount a shock from the direction of wheel travel, the less it dampens. example, if a shock is mounted straight up and down. then the shock 100% effective. if a shock is mounted at a 30 deg angle to the travel of the suspension arc of movement then you have only 75% effectiveness of shock dampening. 45 deg and your shock is only 50% effective.
But.... a shock hoop can be engineered to utilize 2 shocks per side. and if you've raised your lower mounts then you can still use a shock with a decent size of travel range.
in the interest of accuracy, a shock mounted 30° off the plane of motion will provide 86.6% effective damping, and at 45°, 70.7% effective.
 
Rawbrown said:
no offense but you don't have rocks in Florida like we do in the west or even a little further north of you. but if you wanted to Whitey, you could make newer mounts for the tubes and gain probably another 2-3" of shock length on the axle tube. If your mounts were on the bottom edge of the tube and they stradled the ubolt some...
BPE's I consider a temp solution because it cuts about 1/2" to 1" off the upper mount. They call them bar pin eliminators but its still a bar pin and its still fastened in a similar fasion to a stock spring. a few years ago BPE's were a good solution at offering up more shock options because many shock MFG's didn't make every shock with a bar pin option. same goes for those goofy front upper stud style shock mount converter thingy's that let you use the more common eye to eye shocks that were more redily available vs the stock style of bar pin bottom and stud top.
But even bilstein 5150's can be supplied with the stud mount and bar pin type bottoms. same goes for RE monotubes. They come in all flavors and styles.
If you want to raise your lower mounts then something has gotta give. either moving the uppers inboard and doubleing up or putting the uppers through the floor, or some other means of keeping travel.

I try to keep my stuff from dragging throughthe mud here. I lived in Washington state 3 years ago and I'm moving to Maine this December. Maybe after that I could get stationed in California.
 
MaXJohnson said:
in the interest of accuracy, a shock mounted 30° off the plane of motion will provide 86.6% effective damping, and at 45°, 70.7% effective.
i was waiting for someone to do the correct math on those angles:attom::twak:

not to mention that due to the decrease in shock motion/ per travel of axle... this may effect the designed function of any internal "smart" valving that depends on shaft velocity (IAS..etc.). Not sure if this would even be felt or not:eeks1: probably not a problem
 
What about moving the shocks outboard? Say attaching the shocks to the spring plate and running them up into the wheel well? Anybody had any luck doing something like that?
 
I really like the "truck" look on the cherokees when you cut out the back section, but I'm not sure I am ready to start cutting it up yet.

Jenssen I like that set up though, good work
 
I did the truck chop myself with my Friends and a case of beer on a weekend, the shock hoop was orignally built by a friend, but when I jumped it kept tearing off so the pictures above are when evolution machine and fabrication redid it when the sponsered me to run in a tough truck competition,..

They have some whizzy shit there take a peek www.evolutionmachine.com


and oh man does it take abuse!!!!! You can pick up the truck by it :)

qzghf6.jpg
 
Last edited:
Sorry, I did no math. My info on shock effectivness at a given angle was taken from QA1. Just looking back at it, the # they give is called correction factor which I figured as a %. But... That is calculated for spring rates so. I do see the Data that shows your #'s to be correct. Just so you know I didn't try and pull #'s out of my axle...
and as for mounting then more outboard, my tires rub the inside of my wheel wells so thats something to consider.
jjvande said:
i was waiting for someone to do the correct math on those angles:attom::twak:

not to mention that due to the decrease in shock motion/ per travel of axle... this may effect the designed function of any internal "smart" valving that depends on shaft velocity (IAS..etc.). Not sure if this would even be felt or not:eeks1: probably not a problem
 
JENSSEN said:
I did the truck chop myself with my Friends and a case of beer on a weekend, the shock hoop was orignally built by a friend, but when I jumped it kept tearing off so the pictures above are when evolution machine and fabrication redid it when the sponsered me to run in a tough truck competition,..

They have some whizzy shit there take a peek www.evolutionmachine.com


and oh man does it take abuse!!!!! You can pick up the truck by it :)

qzghf6.jpg

how was this mounted before when it tore off? is it bolted on now?
 
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