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Old 08-07-2005, 10:48 AM
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Rear Shock Placement, Angles

Cliffnotes: Trying to figure out shock mount placements, LOL!


I'm in the process of changing my rear suspension out to a set of Posies rear springs and I bought the kit with the shocks and hangers. The instructions call for the bottom shock mount to be located about an inch from the axle saddle, and the top locates at about 9-10" inboard. See photo of installation instructions and note it says "make sure that your shock is compressed to about 12 1/2" with the full weight of the vehicle."

So here's where I am:

With the new springs in place and the u-bolts snugged down I jacked the rear up one side at a time until it just moved the body of the car, indicating to me that I had the weight of the car on the suspension. Then I put a jackstand under each axle and let the jack down. I then started looking at locating the shock mounts. With the shock extended to 12 1/2", the lower shock mount bolt on the highest setting available on the lower bracket, and the top mount bolted onto the shock, I took a look at where everything would fall into place. The only way the top mount could locate inboard 9 or 10 inches with the shock at 12 1/2" is if I move the bottom mount inboard also, like about 8" inboard! I can however get it to reach the frame with the shock at the 12 1/2" length.

It's my understanding that placing the shock in a vertical position would provide the best dampening while moving in a straight line. And placing the upper mounts inboard would help with smoothing out the cornering some. As a general rule is this assumption correct? I'd prefer to mount it like the instructions, but can't see how to do that. Right now, I'm tempted to go to the frame with it like the picture, but figured I'd post up and see what everyone else would do.

ANY ideas or suggestions welcome! Sorry for the novel,,
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Old 08-07-2005, 11:26 AM
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Hey Zip, I am assuming this kit is vehicle specific??

I dont understand your reasons for jacking up the car. I took the instructions to read sitting in its normal state. Which would mean all four tires installed, car fully assembled and car on FLAT ground.

Maybe I just didnt follow what you were doing.

Rich
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Old 08-07-2005, 11:59 AM
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Quote:
Originally Posted by rrmccabe
Hey Zip, I am assuming this kit is vehicle specific??

I dont understand your reasons for jacking up the car. I took the instructions to read sitting in its normal state. Which would mean all four tires installed, car fully assembled and car on FLAT ground.

Maybe I just didnt follow what you were doing.

Rich
Yep, you're right it is vehicle specific. But, I have to add a upper mounting point for the top shock mounts (square tubing, angle iron or whatever to weld the mount to). And this is what I ran into.

That's how I understand it to read too. By putting the jackstands under the rear axle my intent is to put the weight of the body on the suspension, would'nt that be the same as having the tires on and sitting on the ground? If I put all 4 tires on and sit it on the ground there won't be enough room for me to crawl under the car and work. So I'm attempting to simulate having the weight on the suspension, with the car elevated enough to get under it and work.

Thanks,
Phil
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Old 08-07-2005, 12:32 PM
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OK, gotcha.

Yes the jacks would be the same thing as long as the car is sitting with the same front and rear height as normal.


I understand the custom top mount deal.

If I understand you correctly the shock is to short at 12 1/2" from eye to eye to mount where you want?


Seems like it you mount your shock (12 1/2" length) to the bottom mount and tip the top shock in towards the center 9-12", that is where they are saying to put it?? Using trig that means the shock is mounted close to 45 degrees.

That just seems wrong !

Rich
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Old 08-07-2005, 12:57 PM
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You have the pictue now,, I just needed some prodding to get more info out there, LOL. You're right it's about a 45 degree angle if I swing the top inboard about 9 or 10". However my wife and I were just out there looking at it and she suggested maybe they meant to measure from outside on the frame (I've been measuring from the inside on the frame) which would make it alot closer resulting in a better angle on the shock.
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Old 08-07-2005, 01:05 PM
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Well I can see why you would. The "destructions" say inside of the frame.

Personally, I would think that the 12 1/2" part is important as the shock needs to be located in the proper location of the stroke. Most shocks I have looked at are just canted in a little. Seems to me if you do that, it will be OK.

Is there any support at posie?

Rich
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Old 08-07-2005, 01:59 PM
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I haven't called Posies yet, I just ran into this today and thought I'd toss it out looking for some ideas. Heck I doubt anyone is goinna' answer the phone on a Sunday, LOL. And like you, I'm of the same opinion as far as shocks, I'd think that's why they are specific about making sure the shock is compressed to 12 1/2". I'd take that as the "optimum" location in the stroke of the shock.

Here's the difference in the shock angles between measuring 10" inside the frame and 7 and 3/4 after subtracting the 2.25 frame width. I taped a yardstick in place butted up against the frame for reference.
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Old 08-07-2005, 02:03 PM
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Yea that angled one is too much. The other does not look bad. What is this on anyway?

Thats a lot of leif spring !

Rich
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Old 08-07-2005, 06:39 PM
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I'd go with the second shot in the second set of pix. At least in the second set of pix, both shock mount eyes are in the same plane as opposed to 90 degrees out. Lot less chance of snapping off a mounting lug...

Russ
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Old 08-08-2005, 04:40 AM
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Quote:
Originally Posted by rrmccabe
Yea that angled one is too much. The other does not look bad. What is this on anyway?

Thats a lot of leif spring !

Rich
I thought it was excessive too, the second one I could live with but I didn't measure the angle it sits at. I'm going to try to get in touch with Posies today and see what they have to say. It's on a '41 Chevy, the springs on these cars are looooong!!!
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Old 08-08-2005, 04:45 AM
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Quote:
Originally Posted by S10xGN
I'd go with the second shot in the second set of pix. At least in the second set of pix, both shock mount eyes are in the same plane as opposed to 90 degrees out. Lot less chance of snapping off a mounting lug...

Russ
Yeah that's what I was wondering about. I'd rather not put it in a position that may cause other issues besides the ride quality. Actually I'm thinking maybe a little more vertical on it would be better,,,,
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Old 08-08-2005, 06:59 AM
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I put mine as vertical as possible and as far out board as possible..the 12 1/2 inches sounds right with the suspension at ride height which you should be very close to with the car on jackstands..

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Old 08-08-2005, 06:59 AM
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Yea didnt think about it but the bolts have to be parallel to the length of the car. Otherwises as your suspension moves up and down it would not pivot on the bolt.

OK on 41 Chevy. Glad the leafs are not going on the late model Camaro in your pictures !! Not unless you are running moonshine

Rich
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Old 08-18-2005, 05:23 PM
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OK here's how I ended up. I recieved a email reply from Posies and they said to use the setup that resulted in the second picture above. That's measured from outside on the frame which puts the shock 7 3/4" from the inside of the frame. BTW it's worth mentioning here that they were quick to reply!

After considering the replies and doing more searching I decided to do as OMT suggested and put them as vertical as possible. I didn't want the top mount over on the frame so they ended up at 80 degrees.

I used enough angle iron to add a second set of mounts out as far as the 7 3/4" that Posies recommended. I have the mounts on the way, and will add them when they get here. Sort of a "just in case I want to try it there" gas pain I had

Thanks to each of you that replied, I appreciate it! I hated to bring this back up top, but I wanted you guys to know how I went with it.
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Old 09-19-2005, 11:48 PM
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Important question about direction of shock eyes

In your first picture , you show the shock eyes/mounting bolts in different directions. The top bolt is parallel to the axle and the lower bolt is perpendicular. In all the other pix you have them in the same direction. I am getting ready to fab/mount some rear shocks with the eyes in different directions like your top pix. I think I'm getting ready to do it wrong. I think it's a well known fact that they should be both parallel to axle so that they can rotate as the axle flexes up and down. I think I'm the only one who doesn't know this. Someone please help to state the design rule if any for this.
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