LOST JEEPS :: View topic - Rubicon Express Super Flex Rear Control Arms

The whole idea with the adjustable rear arms is to recenter the rear diff in the rear wheel well housing to eliminate the rub we get at the front of the rear wheel wells.By moving the bottom of the axle out you point the pinion down creating(could and will over time) pinion angle problems which lead to early u-joint failure.To solve the pinion angle problem you need to get a custom upper mount(boomerange) to push the top of the rear diff out to,thus putting the pinion angle back where it is supposed to be,also a new driveshaft may be in order to since you only have so much length with the rear slip yoke(not always but is a good idea).

By moving the bottom of the axle out you point the pinion down creating(could and will over time) pinion angle problems which lead to early u-joint failure.

From what I know
The reason people put ADJ control arms on ANY jeep is to adjust pinion angle more so than to recenter the rear axel
I have adjustable upers and lowers on the TJ and am in the process of getting fixed lowers to eliminate problems that I have with adj lowers

If you are having rubbing problems it is from a lack of proper bumpstoping
the stock length is ideal for keeping the rear centered and keeping the bumpstop hitting on the center of the lower pad

Look at it from a stand point of a circle and the control arm is on the outside fixed to the center no mater how far you move the arm it follows the same arc
make it longer and it travels different ,on a different arc so with out proper bumstop spacing it will still rub and you will get a multitude of other problems
like drive line vibes ,failing U-joints just to mention a few

I can not think of how to explain the adjustment on a standard DS ,like the one in a KJ, but in a TJ with a CV shaft ,drive shaft with 3 u-joints, you need to point the pinion up at the rear of the T-case
I think that in the KJ you need to do the opposite ,point it down, but I could be wrong
If some one else knows what I am talking about please correct me if I am wrong

I've had the RE LCAs on the rear for over 2 years now and find they really improve the handling off road. They don't seem to offer more flex but for some reason I feel like I end up with more rubber on the trail that I did without them. A great improvement IMHO.

They're the exact length of the stock ones. I didn't want to monkey around with angles and stuff.

And Jeep owners don't just put these things on to move the axle around. When you look at the flex joints vs stock it just make sense to go with them.

Author:	Jeep4me99 [ Mon Apr 09, 2007 10:41 am ]
Post subject:	Rubicon Express Super Flex Rear Control Arms
So what is the advantage to having these??? Anyone have them?? Opinions???

Author:	KW AV8R [ Mon Apr 09, 2007 10:43 am ]
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I've heard that there are some issues with the pinion angle after the installation of these ... I'm not too sure how bad it is though .........

Author:	Troysterr [ Mon Apr 09, 2007 10:50 am ]
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Advantages: 1) Improved articulation (although I can't explain exactly why). 2) They're adjustable, so you can move the rear tires back slightly, so that they stuff more evenly. (Normally, you'll rub on the front of the wheel well.) 3) Greasable. I don't know about any pinion angle issues. That doesn't make any sense to me, but I'm no expert. They're on my shopping list. Probably next spring.

Author:	KW AV8R [ Mon Apr 09, 2007 10:57 am ]
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They are/were on my shopping list but I'm going to hold off until I know more.

Author:	Signcutter21 [ Mon Apr 09, 2007 12:43 pm ]
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I have them on mine and havent had any probem for over a year they've been on. I just make sure to grease em up after every oil change as a safety precaution. You can feel the rear end move a bit more when taking corners, due to the added flex they allow, so I just dont drive fast around them. You also dont have a spot for a rear sway bar to hook up, but I never had one on anyway. Not sure about the pinion angle aspect either. You set them to stock (or slightly longer) length and insall two bolts per side. I'd like to see more info though if you have it, just as a heads up. Also had heard that JKS has a rear control arm that will fit the KJ too. later, mike

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Author:	tjkj2002 [ Mon Apr 09, 2007 12:52 pm ]
Post subject:
The whole idea with the adjustable rear arms is to recenter the rear diff in the rear wheel well housing to eliminate the rub we get at the front of the rear wheel wells.By moving the bottom of the axle out you point the pinion down creating(could and will over time) pinion angle problems which lead to early u-joint failure.To solve the pinion angle problem you need to get a custom upper mount(boomerange) to push the top of the rear diff out to,thus putting the pinion angle back where it is supposed to be,also a new driveshaft may be in order to since you only have so much length with the rear slip yoke(not always but is a good idea).

Author:	DaveKJ02 [ Mon Apr 09, 2007 4:48 pm ]
Post subject:
tjkj2002 wrote: The whole idea with the adjustable rear arms is to recenter the rear diff in the rear wheel well housing to eliminate the rub we get at the front of the rear wheel wells.By moving the bottom of the axle out you point the pinion down creating(could and will over time) pinion angle problems which lead to early u-joint failure.To solve the pinion angle problem you need to get a custom upper mount(boomerange) to push the top of the rear diff out to,thus putting the pinion angle back where it is supposed to be,also a new driveshaft may be in order to since you only have so much length with the rear slip yoke(not always but is a good idea). I put a set in. Yeah, pushing the wheel back to "recenter" it puts the pinion angle out of specs to the point I have driveline vibrations. I just ordered a custom adjustable bracket from Jeff Daiels Jeep. The braket will allow you to push the top of the diff back, and reposition the tri-link arm back up to where it sits stock (up into the KJ). Overall this should allow the diff to drop more since the tri-link ball joint wont be as maxed out as it is after you lift it. Then an SYE looks like its in the cards too. PS-Dan at Jeff Daniels said he's planning on fabbing some extras to have on stock.

Author:	Troysterr [ Mon Apr 09, 2007 6:07 pm ]
Post subject:
tjkj2002 wrote: By moving the bottom of the axle out you point the pinion down creating(could and will over time) pinion angle problems which lead to early u-joint failure. That's interesting--I guess I haven't been paying close enough attention to your posts. I guess I'll live with the rubbing for now...although I won't be able to live with it forever, because eventually my tires are going to eat all the way through the fender, and then I'll be in a world of hurt.

Author:	jason thompson [ Mon Apr 09, 2007 7:14 pm ]
Post subject:
From what I know The reason people put ADJ control arms on ANY jeep is to adjust pinion angle more so than to recenter the rear axel I have adjustable upers and lowers on the TJ and am in the process of getting fixed lowers to eliminate problems that I have with adj lowers If you are having rubbing problems it is from a lack of proper bumpstoping the stock length is ideal for keeping the rear centered and keeping the bumpstop hitting on the center of the lower pad Look at it from a stand point of a circle and the control arm is on the outside fixed to the center no mater how far you move the arm it follows the same arc make it longer and it travels different ,on a different arc so with out proper bumstop spacing it will still rub and you will get a multitude of other problems like drive line vibes ,failing U-joints just to mention a few I can not think of how to explain the adjustment on a standard DS ,like the one in a KJ, but in a TJ with a CV shaft ,drive shaft with 3 u-joints, you need to point the pinion up at the rear of the T-case I think that in the KJ you need to do the opposite ,point it down, but I could be wrong If some one else knows what I am talking about please correct me if I am wrong

Author:	tjkj2002 [ Mon Apr 09, 2007 7:30 pm ]
Post subject:
jason thompson wrote: From what I know The reason people put ADJ control arms on ANY jeep is to adjust pinion angle more so than to recenter the rear axel I have adjustable upers and lowers on the TJ and am in the process of getting fixed lowers to eliminate problems that I have with adj lowers If you are having rubbing problems it is from a lack of proper bumpstoping the stock length is ideal for keeping the rear centered and keeping the bumpstop hitting on the center of the lower pad Look at it from a stand point of a circle and the control arm is on the outside fixed to the center no mater how far you move the arm it follows the same arc make it longer and it travels different ,on a different arc so with out proper bumstop spacing it will still rub and you will get a multitude of other problems like drive line vibes ,failing U-joints just to mention a few I can not think of how to explain the adjustment on a standard DS ,like the one in a KJ, but in a TJ with a CV shaft ,drive shaft with 3 u-joints, you need to point the pinion up at the rear of the T-case I think that in the KJ you need to do the opposite ,point it down, but I could be wrong If some one else knows what I am talking about please correct me if I am wrong Well for a KJ you need to point it up(the pinion on the rear diff) towards the t-case like a TJ,all vehicles you need to point the pinion up towards the t-case/tranny output.Having the lower rear adjustable arms are fine but when you adjust them out to recenter the rear diff and not move out the upper mount(boomerange) the same amount you point the pinion shaft down torwards the ground thus increasing the driveline angles.DaveKJ02 said he is getting a upper mount that can be adjusted out to help get the correct pinion angle,but than again you are effectively pulling the rear driveshaft out of the t-case most likely requiring a longer driveshaft.

Author:	unixxx [ Wed Apr 11, 2007 8:37 pm ]
Post subject:
When using CV driveshafts, the yokes should be pointed towards the transfer case. However, to compensate for axle assembly rotation during acceleration, the front yoke should be pointed slightly upwards and the rear yoke slightly downwards. When using a standard driveshaft with two cardan joints, the angle between the transfer case and driveshaft should match the angle between the yoke and driveshaft.

Author:	lilmatty [ Wed Apr 11, 2007 10:27 pm ]
Post subject:
I've had the RE LCAs on the rear for over 2 years now and find they really improve the handling off road. They don't seem to offer more flex but for some reason I feel like I end up with more rubber on the trail that I did without them. A great improvement IMHO. They're the exact length of the stock ones. I didn't want to monkey around with angles and stuff. And Jeep owners don't just put these things on to move the axle around. When you look at the flex joints vs stock it just make sense to go with them.

Author:	tjkj2002 [ Wed Apr 11, 2007 10:37 pm ]
Post subject:
lilmatty wrote: I've had the RE LCAs on the rear for over 2 years now and find they really improve the handling off road. They don't seem to offer more flex but for some reason I feel like I end up with more rubber on the trail that I did without them. A great improvement IMHO. They're the exact length of the stock ones. I didn't want to monkey around with angles and stuff. And Jeep owners don't just put these things on to move the axle around. When you look at the flex joints vs stock it just make sense to go with them. Yes there is nothing wrong with running them if you set them at the stock length,there joints will flex better than the OEM's rubber bushings.Problems will occur when you lengthen them without lengthing the top to.

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