This has probably been addressed before, but with all the dead build threads I can't find it. What is the advantage of the shackle design that wraps up to the top of the frame in the rear? Just curious.

Leni

One advantage, if set-up correctly, keeps the shackle from camming under on itself when you back up into something. The frame limits it, yet the shackle can still fully extend for the spring.

Also lowers the vehical without taking leaves out of the spring pack.

And looks trick as shat if done properly by either of the above guys.:D

And looks trick as shat if done properly by either of the above guys.:D

Like this...done by Tool Box Guy :D

http://pics.montypics.com/albuquerque_jim/2008-11-22/1227374067_hpim1116.jpg

Yeah...just like that. It looks awesome, don't get me wrong, but I knew there was a reason behind it besides looks.

watch your shackle angle... There are cons to the above posted setup if you set it up wrong.

watch your shackle angle... There are cons to the above posted setup if you set it up wrong.

Please elaborate...

Laid back shackle angles hurt climbs and helps you roll.

Laid back shackle angles hurt climbs and helps you roll.

So, the straighter the shackle, the better it climbs? I imagine this is due to the suspension not "un-loading" as much...is that accurate?

How does this look?

http://pics.montypics.com/albuquerque_jim/2008-11-18/1227065631_hpim1115.jpg

Please bear with me, this is my first leaf sprung rig. Thanks for your resonses.

When I got those shackles from Brett he told me to mount the front hangers so that the long part of the shackle was as vertical as possible.

Don't forget to account for any added weight in the rear of the finished rig.

This is good 'put. There's more going on with this system though. Spring preload plays a role hear also. In what I see Jim you have a alot of arch/preload to the spring it's self. This will apply some down force on the center line of the axle thus some what compensating. But the advice is correct in that the geometry of how a 'laid back' shackle effects anti-squat. Think of it this way, the shackle design isn't to flatten out as the spring compresses, it's to hindge the spring and allow the spring to compress providing the needed anti-squat. The shackle will simply rotate until it's done, the spring however is the kinetic (stored energy)piece to this link. You need the spring to hold the rear up as you climb. IMHO

Visualize this as your "Shackle Angle". It puts it a little more into perspective of a regular shackle setup.

I would say that you have too much shackle angle. It will ride better, but it won't climb as well. It just depends on what you are setting it up for.

It's not just the angle of the shackles but the radius in which they rotate. I think it's a great start and I'd run it. If it seems to squat under load you have options. Decrease shackle length, or increase spring rate. For fun I could calc it, but if you wanted an engineered system you'd of bought rather than built it right.

I would say that you have too much shackle angle. It will ride better, but it won't climb as well. It just depends on what you are setting it up for.

I see your point. I will see how this handles and go from there. I don't want to start rebuilding things before I even finish it.

It's not just the angle of the shackles but the radius in which they rotate. I think it's a great start and I'd run it. If it seems to squat under load you have options. Decrease shackle length, or increase spring rate. For fun I could calc it, but if you wanted an engineered system you'd of bought rather than built it right.


Decreasing shackle length will lay the shackle back even more. I had a slightly laid back shackle begining of the season and straighten'd rigth up almost vertical, made a big difference on bumping ledges and big climbs.

So If a person were to go from a 6" shackle to say a 7" or even 8" shackle in the rear to straighten the angle up what would the disadvantages be? Would the rig be less stable side hilling etc? I'm just curious on that. My rig sags about an 1"-2" lower in the back where the rear springs settled more than the front and shackles are easier to install then reinstalling the leafs I removed.

Depends on their design and your rigs primary purpose. But as a general rule shackles are not intended to provide lift, that's the job of the spring. Now, can you get away with it without troubles, sure. You mention that you removed some leafs from the pack. Keep a couple things in mind here, you modify the engineered design of that particular pack. The lift, the anti-wrap, and the anti-sqaut are all impacted by doing this. Is this rig driven on the road? If so, then the 6" shackles you already have may be more than what's safe. Need more info to provide an educated response.

I understand that the original question was about the design of the rear shackle which turned into a disscusion about shackle angle. What about the shackles on the front springs, does this apply to those also.

I understand that the original question was about the design of the rear shackle which turned into a disscusion about shackle angle. What about the shackles on the front springs, does this apply to those also.

To a certain extent, yes. Does the front shackle angle effect how the rig will climb? Not so much, because all the weight is on the rear when climbing. The main thing to remember is, if the shackle is straight up, the spring is doing all the work. This is good. If the shackle is laying back (like in the picture) it is adding progressiveness to the spring. In other words, the chassis will move up or down more than the spring, making the spring rate less. This is why the rig will ride better with more shackle angle.
In my opinion, if you want performance the shackle angle should be straight up at ride height. Now you don't want the shackle to cam foreword on rebound as well as cam backwords on compression so you might have to adjust the shackle angle at ride height to accomidate that.

Is that as clear as mud? You will also find that the more people that you ask this question, the more different answers you will get.

To a certain extent, yes. Does the front shackle angle effect how the rig will climb? Not so much, because all the weight is on the rear when climbing. The main thing to remember is, if the shackle is straight up, the spring is doing all the work. This is good. If the shackle is laying back (like in the picture) it is adding progressiveness to the spring. In other words, the chassis will move up or down more than the spring, making the spring rate less. This is why the rig will ride better with more shackle angle.
In my opinion, if you want performance the shackle angle should be straight up at ride height. Now you don't want the shackle to cam foreword on rebound as well as cam backwords on compression so you might have to adjust the shackle angle at ride height to accomidate that.

Is that as clear as mud? You will also find that the more people that you ask this question, the more different answers you will get.

Good input...for this rig I want a combination family buggy that also meets competition specs. So this is probably a good balance.