can extended front shackles affect caster THAT MUCH???

[Greg72]

If you're trying to take out excessive caster you could also try spacing DOWN the front spring hangers you built....

That would have the same effect as a shim (depending on how THICK of a spacer would be required to get you into the correct range)

I'm not sure which would be the easier way to test your theory....I apologize for not reading the whole thread. Some of those guys (most notably Greg72) sure do write a LOT to answer a simple question!!

 

[cegusman]

When doing my 52" spring swap with a 7.25" shackle my caster went to -14 degrees, Death wobble sucked. I reinstalled my 4 degree tapered zerorates and got it to -10 degrees caster and the death wobble happens a lot less now. I do need to change my tierod and ends due to mine being bent so I am hoping it will help cure it some more. If not I will get some 10 degree zerorates to get it back to the stock -4 degrees.

 

[RockinChevy]

When doing my 52" spring swap with a 7.25" shackle my caster went to -14 degrees, Death wobble sucked. I reinstalled my 4 degree tapered zerorates and got it to -10 degrees caster and the death wobble happens a lot less now. I do need to change my tierod and ends due to mine being bent so I am hoping it will help cure it some more. If not I will get some 10 degree zerorates to get it back to the stock -4 degrees.

Hey cegusman, how much lift are you getting with those 7.25 front shackles and 6" rear shackles and shackle flip?

 

[79k20350]

Being a science nerd and all that jazz, it's trigonometry to the rescue:
arc = difference between shackle length; not precise but should be good approximation given the relationship between arc and radius; in this case 2" (6" shackle vs. 4" shackle)
radius = distance between spring eyes (I assume 47", not sure?)

arc = (angle/180) x radius x Pi; solve for angle:

angle = (arc x 180) / (radius x Pi)

angle = (2" x 180) / (47" x 3.1415) = 2.438 degrees of change in the angle at the front spring eye, which should result in an additional 2.438 degrees positive caster angle

within limits, each 1" in additional shackle length over 4" would add 1.219 degrees to the caster angle

it would remover castor... so it would be adding negative castor

 

[cegusman]

Hey cegusman, how much lift are you getting with those 7.25 front shackles and 6" rear shackles and shackle flip?

Around 5" - 5.5" That is with the zerorates front and rear.

 

[79k20350]

Nope, pinion goes down with a longer shackle.

yeah im an idiot... Originaly thats what i thought was positive/ negative but when i was looking at gregs post it through me off... oh well

 

[RockinChevy]

Around 5" - 5.5" That is with the zerorates front and rear.

Thanks that's exactly the lift I want to get when I'm done with my 52s and 56s with zero rates. One more thing, for the 6" shackles, did you flip the brackets around so they're angled towards the rear or left them angled towards the front? I have 6" shackles but I can't see how they'll work with 56s and shackle flips angled to the rear..... that's what's keeping me from putting them on..
Sorry for the hijack if I'm not on point with the original thread title...

 

[k204dr]

So, does a 85 1008 d60 have the same caster as a 89 3500 d60? just need to know if they changed anything other than just lengthening the shackles?
I don't have any deathwobble, but I have to chase my truck around on the road.

 

[cegusman]

Thanks that's exactly the lift I want to get when I'm done with my 52s and 56s with zero rates. One more thing, for the 6" shackles, did you flip the brackets around so they're angled towards the rear or left them angled towards the front? I have 6" shackles but I can't see how they'll work with 56s and shackle flips angled to the rear..... that's what's keeping me from putting them on..
Sorry for the hijack if I'm not on point with the original thread title...

Answered your pm but will answer here also. I flipped the brackets from side to side. Here is a pic of the shackle angle:

 

[cegusman]

So, does a 85 1008 d60 have the same caster as a 89 3500 d60? just need to know if they changed anything other than just lengthening the shackles?
I don't have any deathwobble, but I have to chase my truck around on the road.

Both willl have tha same castor angle, sould be around -4 to -6 degrees. Anything more and death wobble has a chance to visit you.

 

[Citizen Rider]

I was looking at doing the shackle angle/move the frame hanger thing this weekend. Based on the measurements I took you would probably between 5 & 6" shackles. That's with my 2.5" lift front springs.

I think the 7.25" shackles are for the 52" swap where the spring is longer and hence the need for longer shackles than you would with stock length springs.

I moved the mount on my blazer, with 6" stock length springs, and used a 7.25" shackle. When the springs are flat, i actually just miss the frame with the spring eye. I also reused the upper front hole instead of the lower one.

 

[mrk5]

I was looking at some of the pictures showing the different shackle angles and I was curious about how the longer shackles were affecting caster.

I went out and measured my truck with the stock shackle setup. Measuring from the center of the existing big hole through the frame down to the center of the spring eye it is 4.25", which is what I'd expect.

So I used 2 pictures and scaled out how much further the spring eye is from the stock location.

I can see how the caster angle would be so far off after changing the shackle angle and longer shackles.

I noticed in a product review here on CK5, Hill Offroad's extended front shackles came with 4° shims. http://coloradok5.com/hill4wheeldrivereview.shtml

I think when I do my 52s, I'm going to drop the front hanger an 1" or so, too. Especially since the General is still driven to and from the trail I don't need DW coming to knock at my door.

 

[twoslo4five0]

man good stuff right here guys!!

 

[jamber2541]

Being a science nerd and all that jazz, it's trigonometry to the rescue:
arc = difference between shackle length; not precise but should be good approximation given the relationship between arc and radius; in this case 2" (6" shackle vs. 4" shackle)
radius = distance between spring eyes (I assume 47", not sure?)

arc = (angle/180) x radius x Pi; solve for angle:

angle = (arc x 180) / (radius x Pi)

angle = (2" x 180) / (47" x 3.1415) = 2.438 degrees of change in the angle at the front spring eye, which should result in an additional 2.438 degrees positive caster angle

within limits, each 1" in additional shackle length over 4" would add 1.219 degrees to the caster angle

so going back to the front diff, you would need a 2.5 degree shim for a 6" or a 5.5" shackle to be @ factory specs and we would be talking about a steel shim

 

[RootBreaker]

I know a while back before I bought my ord zero rates I needed to test lifting my truck up 1 more inch.... the deal with the test in NJ will only allow my door to be 33" off the ground... so I wanted to lift the truck 1 inch and see what happens...

well I went from the stock shackle (4"?) to 2" longer... took the truck for a ride...

dayumn.. it wandered all over the road.. turns were freaky.....
took them off..... as it did tell me that my ord zero rate will put me ok....