okay so WTF?

[Kaldar142]

So, i put on my ground control coilovers and everything is great, except............

I didn't have the spacers and poly bushings to put in the rear konis, so i did that today when they arrived today.

Although, there is a slight problem... the springs don't sit flush on the perch, its almost like the axle is off center or something. the rubber thing won't allow the spring to sit flush.

check out this bullshit...

 

[Kaldar142]

and heres a money shot of my rearend

 

[EagleStroker]

Dumb question, are you sure it's not upside down? And it looks slow....

 

[Kaldar142]

its exactly the same both sides, i can make it sit flush if i hold it there but as soon as i let go it will go back

 

[j-stang]

does it straighten up when you put some weight on it? maybe try jacking the axle up an see if putting the cars weight on it will line things up where they are suposed to be?
i dont know anything about this set up but am looking into it fwiw

 

[Kaldar142]

they stay exactly where they are when i jack it up

 

[SoundGuyDave]

I *THINK* I know what the problem is... I can't see for sure, but it doesn't look like you have adjustable control arms, which may be what you need.

When you lower the car, it tends to do two things to the rear axle: 1) roll the pinion angle towards positive (pinion points more upwards), and shift the axle rearward relative to the spring pockets.

To correct (properly) you need to have all three of the arms adjustable, and start by re-centering the axle over the spring pockets with the lowers (watch your thrust angle!). THEN adjust the upper for pinion angle, and recheck the relationship between the spring perch and the axle pad again. Repeat both of the above as necessary, and it's faster if you do it with the suspension loaded. Once you're done, re-adjust your Panhard rod... Oh, wait, you've got one of them new-fangled Watts Links in there; never mind!!

From the way the spring is sitting in the well, I would bet that's your problem, OR, and this is a long-shot, see if during the shock install, the spring fell off the locator pad up top and is wedged between the locator and the front of the well. If it's sitting pretty around the donut up top, and the nipple is poking down into the spring well, then check your rear end for center under the wells.

That's all I've got offhand... I'll be tackling that exact project in a couple of months, so I am looking hard at this for potential problems...

 

[SoundGuyDave]

Okay, I can see it now, it's definitely the rear axle positioning... In your first pic, look where the bump-stop rubber is relative to the flat of the frame. They SHOULD be lined up! Since they're not, that pretty much indicates what the problem is... Hopefully, you've got adjustables all the way around and can dial that out.

 

[Kaldar142]

i have the adjustable UCA, which is all i thought i needed.

I have the pinion angle corrected, but i can see what you're saying... i was thinking it had something to do with that, because it just wasn't making sense but then again my car has all aftermarket suspension.

SO you think i need a set of adjustable LCAs? and what exactly is thrust angle?

thanks for the insight dave, i think you're right

 

[Kaldar142]

Hey dave, why was it fine before with my other springs though?

 

[DusterRT]

Here is mine for reference, note though the axle is supported by the jack but it doesn't look it's at much of a different level than yours. Yours does look off quite a bit, but I think some adjustment of the UCA could take care of it (at that angle, a little adjustment can rotate the axle quite a bit now that I think about it). My adjustable LCA's were set at stock length; I'm not sure if the CHE fixed UCA is longer/shorter than stock or not.

 

[SoundGuyDave]

Kaldar: I'm not going to say categorically that you NEED adjustables, but I would bet on it... Also, do you have a higher-res photo of the entire rear suspension? I'm not sure what, but something looks off to me, and I'd appreciate the opportunity to look a little closer. Same angle as the "money shot" would be awesome, just higher-res so I can blow it up without pixelating... Thrust angle is the differential between where the front wheels and the rear wheels are pointing. If you've ever seen old B-bodies dog-tracking down the street, that's what it's about. We want 0.0* of thrust angle, so that when you're going straight, your rear tires point in the exact same direction as your fronts. If, for example, the driver's side LCA was an inch longer than the passenger side, then the rear axle would NOT be perfectly perpendicular to the centerline axis of the car. Follow? Easiest way to measure is to put the car up in the air, with the tires on ramps so that the suspension is loaded, and use a plumb-bob. Use the plumb directly under the center of each ball joint, and make a mark on the floor. Now, do the same, but under the center of the LCA mount on the rear axle. Now, cross measure (driver's front to pass rear, etc.) and then compare your numbers. If the differential is less than about 1/8", you're golden. As another quick check, measure the center of the wheel centercaps front to rear on each side, these should be within roughly 1/16" of each other.

As to why it was fine with your stock springs, I'm not sure, but I'll venture to guess that with a longer free length, they didn't appear to be as cocked as the shorter ones are, so it just may not have been as visually noticeable. Also, with the adjuster being concentric with the spring it's MUCH more noticeable than having something off perpendicular. At least to my eyes, it's easier to see something amiss on a parallel than a perpendicular.

A few questions so that we can help collectively peek over your shoulder while you fix this thing...
Whose LCAs are they?
What else was changed out in back at the time you did the springs?
Do I see LCA relocation brackets (whose?), and if so, is it possible one of them is tweeked?
Are both sides equally off, or is it just the driver's side?
Can you see witness marks from the spring rubbing the back of the spring bucket in the chassis?
Also, this is a long-shot, again, because you seem pretty together with the mechanical end, but when you did your pinion angle, you did use the angle difference between the output shaft and pinion shaft flanges, and not just slap a level on the bottom of the diff, right? Running excessive positive pinion angle *could* tip the spring perch, but I don't know if it would do that much. Also, that wouldn't account for how FAR off your bump-stops are from the frame "target."

Car's never been crashed, right?

 

[Kaldar142]

they are both exactly the same side to side, car has never been crashed.

i took the driveshaft off and measured it on the flanges with a digital angle finder. unless i did it wrong and ended up extending it out too much somehow, i did turn it quite a bit because from my understanding it was out of alignment since it had never been set before. this was the ONLY thing prior to installing coilovers that i did. i used to have d-specs/pro-kit, which had no problems but they had alerady been on my car at the time of me messing with the pinion angle

i can send you a bigger picture of that one, the one thats hosted isnt that big.

they are BMR non-adj lcas and CHE relocation brackets, i believe they are ok.

 

[Pony DNA]

they are both exactly the same side to side, car has never been crashed.

i took the driveshaft off and measured it on the flanges with a digital angle finder. unless i did it wrong and ended up extending it out too much somehow, i did turn it quite a bit because from my understanding it was out of alignment since it had never been set before. this was the ONLY thing prior to installing coilovers that i did. i used to have d-specs/pro-kit, which had no problems but they had alerady been on my car at the time of me messing with the pinion angle

i can send you a bigger picture of that one, the one thats hosted isnt that big.

they are BMR non-adj lcas and CHE relocation brackets, i believe they are ok.

Hi Kaldar,

I think SoundGuyDave has it about right, you need to check to see that your chassis is square and install some adjustable LCA's. From the images you posted your axle is rotated with the pinion up. Part of the problem is the fixed LCA's and the LCA relocation brackets. You need the adjustable LCA's when using the CHE LCA brackets because they move the pivot point on the axle.

With all the poly bushings you are going to have installed the pinion angle should point down only about 1 degree when compared with the driveshaft. CV joints on the drive shaft are not as sensitive to misalignment as conventional U-jointed D.S. would be.

I would suggest a Steeda adjustable LCA with a poly/rod-end combination. They do not have a part number for this setup but if you call Steeda and ask for Gus he can hook you up. You could also go with a poly/poly setup but this is is not as bind free as the poly/rod-end combo.

HTH!

 

[DusterRT]

Thrust angle is the differential between where the front wheels and the rear wheels are pointing. Easiest way to measure is to put the car up in the air, with the tires on ramps so that the suspension is loaded, and use a plumb-bob. Use the plumb directly under the center of each ball joint, and make a mark on the floor. Now, do the same, but under the center of the LCA mount on the rear axle. Now, cross measure (driver's front to pass rear, etc.) and then compare your numbers. If the differential is less than about 1/8", you're golden. As another quick check, measure the center of the wheel centercaps front to rear on each side, these should be within roughly 1/16" of each other.

they are BMR non-adj lcas and CHE relocation brackets, i believe they are ok.

I installed my CHE LCA brackets with the LCA's adjusted to factory length; and they were waaay off, so much that you could see something didn't look right. I measured a 5/8" difference side to side..all my rear suspension links are CHE and I've been very happy with everything, but gotta say that's disappointing! I would have sent them back if I hadn't gotten the adjustable control arms..I probably should have but I just wanted to be done with it, haha.

The scientific way to measure is to follow one of Dave's methods; or you can try my quick-n-dirty way of doing it. Take a machinists rule, stick it on top of the plastic rocker trim and measure off the flange of the wheel opening to the tire (measure off the steel quarterpanel/wheelhouse joint, not the rocker trim). Yours may not be as far off as mine, but I can pretty much guarantee it's going to be off..anyway after I did this I took it in to the alignment shop and my thrust angle was .02 degrees, which was good enough for me (so unless I got lucky this is a reasonably accurate and much quicker/easier reference point to measure from).

 

[Random Asshole]

holy hell, wtf are you guys doin here?

This is throwing me off the more that I look at these pictures.

The first shot makes the rear axle look so cockeyed that it doesn't even look like you can get the tire on without hitting the car.

When comparing Duster and Kaldars car, I notice the spring seat/gold collar don't look the same between the two. Dusters has holes in it almost making me think it's made of two halves bolted together. Is it just a generation gap or possibly a wrong part?

Dusters spring seat also appears to be a little bit higher than Kaldars. Hard to tell though. Tried counting threads but it;s not clear enough.

Then there's the thrust angle. If the rear axle was like a "/" and not "|" (in relation to the front), then the springs be angled opposite on each side. So that would leave pinion angle, yeh? I understand what was said about lowering the car and what it did to the location of the spring pockets in relation to the seats on the axle, but would it really affect it that much? I dunno, yogi. If we are talking greater than 2.5in drop, then I could agree. I just walked out and looked at my car. With a 1.3-1.5 drop and ALL stock arms, my springs appear pretty perpendicular to the road. I never noticed how far upwards my pinion flange was pointing up at the sky with the car on the ground. I think I know how I may have toasted the joints on my DS..lol.

OR the spring is just cocked in the bucket up top.

I'm done pretending I know what I'm talking about and reposting pretty much was Dave said.

 

[Kaldar142]

Mine are adjusted lower than dusters, it's the same part.

So basically I need to get adj. lcas and shorten them to bring it closer, then measure my pinion angle.

So you don't think that maybe I adjusted my UCA incorrectly? It couldn't be that far off by only adjusting the uca?


Also, random you bring a good point, my axle is shifted very far back that it puts thw wheels close to the rear bumper, but it's the same on both sides.

 

[kevinatfms]

check your pinion angle and adjust your UCA neg to achieve your desired angle, do it with the weight on the rear axle

 

[SoundGuyDave]

Okay, it looks like we're starting to close in on the issue and the solution... If I were you, here's what I would do:

1) Temporarily remove the relocation brackets, and see if that centers your axle out (at least visually). This costs nothing, and if it changes nothing, then we have other issues. If removing the brackets puts the axle in the right spot, then you know that you'll need adjustable lowers to run the CHE brackets, and that CHE's design on the bracket was less than well thought out. The holes in the bracket should describe an arc based on the front of the rear LCA. In theory, you should be able to pin any of the holes and not change the location of the rear end. Not everybody managed to get that right... Both Steeda and BMR got that right, but I can't attest to CHE. This could be interesting!
2) If, however removing the brackets does NOT reset the axle position, then I would pull one of the lower arms and compare length to the OE piece. You should be able to set them side-by-side, and run bolts through both of them without problem. If you can't, or the CHE arm is visually longer, then that's your problem.
3) If the brackets are right, and the control arms are right, then your UCA adjustment is way off for some reason. Assuming that everything worked correctly stock, the chassis mount points are in the correct location, and absent crash damage, that couldn't have changed, so...

I have no doubt that you did it right, but I'm going to restate the pinion angle measurement procedure just to get it out in the open for anybody that may be attempting it! With the car in the air, but loaded on the rear suspension (and with the chassis sitting level! Think ramps rather than jackstands.) remove the driveshaft, and use an angle-finder to measure the angle of the transmission output shaft flange relative to the ground. Let's say, for sake of argument, that it's 2*, and points slightly towards the ground. Call that "-2*." Now, measure the pinion shaft flange the same way, and compare the two. In this case, for example, the angle is 1*, and the flange points up slightly, so we'll call that "+1*." Add the two numbers together, and THAT is your net pinion angle, in this case a net -1*. For auto cars, you want around -1 to -2*, and for sticks, between -2 and -3*. If you run poly/rod control arms, reduce the angle by one degree, (-1 to -2 for sticks), and if all rod-end, just set it at -1 and be done. What you're doing with pinion angle is pre-loading the rear suspension so that under acceleration, you wind up with a net ZERO pinion angle, and the different bushing materials will have different rates of deflection.

With a little luck we can figure this out and get you all sorted!

 

[05BlackGT]

I have the same GC setup. If the springs are properly seated up top, then yes, the pinion angle is way off. I also got confused with all the math and ended up with a crazy angle, so now adjust mine by sight, then take measurements to verify and adjust as necessary.