Hossbaby50
3/4 ton status
az-k5 is running 56's in his stock 52" shackle flip brackets with a longer shackle. It works great and the shackle doesn't collapse.
Harley
Harley
CK5
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56" rear springs installed now have shackle questions...
- Thread starter k5-newbie
- Start date
Move the hanger forward (so your spring goes flat before your shackle does), run an IFS chevy shackle (longer), and move the hanger upward (so you have less lift and less pinion angle).
Here is a 64" Chevy spring with a IFS Chevy shackle on it. The front hanger is moved 3.5" forward. The springs droop ~7" more than what is seen here and that is with 31" rubber and no calipers or anything. I expect the rear end to sag 2-3" when it's loaded. The springs are way too stiff. I already removed one leaf and I'll probably be removing another depending on what happens after it is loaded. With my fat ass on it the thing only dropped about 1". At the same time my Dad and I can lift it up by hand so one tire comes off the ground.
Here is a 64" Chevy spring with a IFS Chevy shackle on it. The front hanger is moved 3.5" forward. The springs droop ~7" more than what is seen here and that is with 31" rubber and no calipers or anything. I expect the rear end to sag 2-3" when it's loaded. The springs are way too stiff. I already removed one leaf and I'll probably be removing another depending on what happens after it is loaded. With my fat ass on it the thing only dropped about 1". At the same time my Dad and I can lift it up by hand so one tire comes off the ground.
az-k5
1/2 ton status
7.5" hole to hole
It works perfect. Same lift as a normal shackle flip, no collapsing of shackles. I used a triangle set up to figure it out and threw in a little CEE for fudge factor.
4" (the spring length increase) is leg 1
5.5" (the stock shackle length) is leg 2
5.5²+4²=46.25
sqrt(46.25)=6.8"
adding another ~.5" to the shackle for CEE fudge only makes it .75" lift wich makes up for my D60 spring pearches.
It works perfect. Same lift as a normal shackle flip, no collapsing of shackles. I used a triangle set up to figure it out and threw in a little CEE for fudge factor.
4" (the spring length increase) is leg 1
5.5" (the stock shackle length) is leg 2
5.5²+4²=46.25
sqrt(46.25)=6.8"
adding another ~.5" to the shackle for CEE fudge only makes it .75" lift wich makes up for my D60 spring pearches.
Shackle angles are soooo fun.
To solve the subject problem, you need to move the bracket back. Going to a longer shackle will help, and at some point would solve the angle problem without having to move the brackets. A combination of the two will probably be the best solution.
You really need to know the actual length of the main leaf on those springs when stretched flat. Once you have that, disconnect the spring from the shackle, run a tape measure from the center of the main eye bolt of the spring to the center of the lower shackle eye. Hold the lower shackle eye at the length of the main leaf, let's just say 56" for this example. With everything set up the way it is now, you're going to find that the shackle won't even reach to the 56" point on the tape measure. What you're looking for is about a 60-70 degree angle between the shackle centerline and flat main leaf.
So, set the bottom end of the shackle at the flat length of the main leaf on the tape, 56" in this example, and then swing the top of the shackle forward from vertical to about 60-70 degrees and that's where the flip bracket needs to be.
Starting with a longer shackle will make it work a bit smoother, about 10% of the spring length is a good baseline point.
Now a little bit of shackle angle theory, hopefully enough to help and not hurt.
You have to be careful about laying the shackle down a long way if you want to have any compression travel past the point the main leaf goes flat. With a long shackle laying way back, anytime the spring has to go into a reverse arch, the effective spring rate will skyrocket due to the fact that as the spring tries to shorten up and draw the shackle forward, it's bringing the shackle eye downward a long way which is trying to pick the truck up. Basically if you want to reverse arch the spring at all, you need to have the shackle a bit more straight up and down.
Another note, with any spring close to the stock arch, the axle will move forward a negligible amount, usually 1/4" or so. With a lift spring with a deeper arch you will see the axle move forward some amount, determined by the arch in the spring. On some lift springs the center pin is offset and it's easy to just put the long part of the spring to the front to move the axle back so that it looks centered at ride height. Otherwise a zero rate will do this too.
one more thing, I would typically NOT recommend moving the axle back in a K5 more than 3-4" because of clearance to the gas tank, this particular truck has a relocated tank that hasn't been mentioned yet, that's how he can get away with moving the axle back 5" or more.
To solve the subject problem, you need to move the bracket back. Going to a longer shackle will help, and at some point would solve the angle problem without having to move the brackets. A combination of the two will probably be the best solution.
You really need to know the actual length of the main leaf on those springs when stretched flat. Once you have that, disconnect the spring from the shackle, run a tape measure from the center of the main eye bolt of the spring to the center of the lower shackle eye. Hold the lower shackle eye at the length of the main leaf, let's just say 56" for this example. With everything set up the way it is now, you're going to find that the shackle won't even reach to the 56" point on the tape measure. What you're looking for is about a 60-70 degree angle between the shackle centerline and flat main leaf.
So, set the bottom end of the shackle at the flat length of the main leaf on the tape, 56" in this example, and then swing the top of the shackle forward from vertical to about 60-70 degrees and that's where the flip bracket needs to be.
Starting with a longer shackle will make it work a bit smoother, about 10% of the spring length is a good baseline point.
Now a little bit of shackle angle theory, hopefully enough to help and not hurt.
You have to be careful about laying the shackle down a long way if you want to have any compression travel past the point the main leaf goes flat. With a long shackle laying way back, anytime the spring has to go into a reverse arch, the effective spring rate will skyrocket due to the fact that as the spring tries to shorten up and draw the shackle forward, it's bringing the shackle eye downward a long way which is trying to pick the truck up. Basically if you want to reverse arch the spring at all, you need to have the shackle a bit more straight up and down.
Another note, with any spring close to the stock arch, the axle will move forward a negligible amount, usually 1/4" or so. With a lift spring with a deeper arch you will see the axle move forward some amount, determined by the arch in the spring. On some lift springs the center pin is offset and it's easy to just put the long part of the spring to the front to move the axle back so that it looks centered at ride height. Otherwise a zero rate will do this too.
one more thing, I would typically NOT recommend moving the axle back in a K5 more than 3-4" because of clearance to the gas tank, this particular truck has a relocated tank that hasn't been mentioned yet, that's how he can get away with moving the axle back 5" or more.
k5-newbie
1/2 ton status
Ahh, Dr Watson is here 
, Thanks soooo much for chiming in. I was planning on moving the shackle flip back along the frame, just wasnt sure how far. Now we have something to go by. I will post up results as soon as we finish.
BTW, do you think I will have too much axle wrap since i'm running the springs backwards? i know I need to "roll" the perches on my 14 bolt to get a better pinion angle, just wasn't sure if I was gonna need a trac bar.
Thanks
Ben
, Thanks soooo much for chiming in. I was planning on moving the shackle flip back along the frame, just wasnt sure how far. Now we have something to go by. I will post up results as soon as we finish. BTW, do you think I will have too much axle wrap since i'm running the springs backwards? i know I need to "roll" the perches on my 14 bolt to get a better pinion angle, just wasn't sure if I was gonna need a trac bar.
Thanks
Ben
Is that flip mounted in the 52" holes? Kinda looks like it, so I guess you flipped side to side. It's been done, but I have no idea what springs or how it turned out. That definitely shouldn't be happening and the hanger needs to move back (or front forward).
Longer shackles would provide compensation for the spring being on the back side of the arch (due to backwards springs) and move the pinion up a bit. But you don't want to get too long or you'll have new problems. Still, might get it in range for a degree shim.
You also need to be aware (and may already know) that the pinion is going to rotate down during axle droop which may bind the u-joint. As already stated, the long side in front also reduces its ability to control axle wrap.
Longer shackles would provide compensation for the spring being on the back side of the arch (due to backwards springs) and move the pinion up a bit. But you don't want to get too long or you'll have new problems. Still, might get it in range for a degree shim.
You also need to be aware (and may already know) that the pinion is going to rotate down during axle droop which may bind the u-joint. As already stated, the long side in front also reduces its ability to control axle wrap.
What was the final fix? How far did you have to move the brackets back? Are you still running the brackets switched from side to side?
TIA!
TIA!
Bhintz
1/2 ton status
I just saw this I just did the swap myself but just with the echobit flip flipped backwards and my shackle angle looked like that, so I got these shackle from summit it gave me the 2 extra inches of lift that I needed and put my shackle angle perfect IMO http://store.summitracing.com/default.asp?target=partdetail.asp&part=SUM%2DG756clarkjw24 said:Bhintz just put this same setup on his. Maybe he'll post up with some pics also. BTW I can tell that its moved back.
Edit: I thinks some people also added a longer stronger shakle with this setup.
nvrenuf said:
TTT
k5-newbie
1/2 ton status
nvrenuf said:
sorry..just saw this post, I moved the shackle flip back 2 1/16" on each side. The shackle is almost 90 degrees, and I think I am gonna move them in a little more to get more of an angle, just haven't had time to mess with it lately. I will post pics though when I finish and if you need something nvrenuf, just PM me
Excellent!! Thanks for the info. 
I've been watching yours evolve because of the similarity (flip with lift springs). I was thinking of moving the brackets back about 3" hoping for a near correct shackle angle. My biggest problem is I'm working with a frame only so I cannot check the shackle angle with actual vehicle weight.
I've been watching yours evolve because of the similarity (flip with lift springs). I was thinking of moving the brackets back about 3" hoping for a near correct shackle angle. My biggest problem is I'm working with a frame only so I cannot check the shackle angle with actual vehicle weight.
k5-newbie
1/2 ton status
here is a pic the way it sits now. I still plan on moving the shackle forward about a half inch to get a better shackle angle.
