Pirate 4x4 banner
1 - 20 of 32 Posts

·
Registered
Joined
·
27,625 Posts
Discussion Starter · #1 · (Edited)
Anyone interested in a discussion about leaf spring tech? I'm not talking about what junkyard combos work best or how to lift my yj. I'm talking about getting the most out of a properly designed setup and how to get there. I've built a lot of leaf-sprung rigs and after spending money on good springs and shocks, I was very happy with the results. After deciding which springs you are going to run, what's the next step? What are the different options and configurations ( and the compromises of each).

Front axle:
-Shackle in front vs. Shackle in back?
-Shackle configuration (specifically mounting point, location and reference to other suspension components)
-Shackle length as more than a function of packaging, more of a function of travel?
-Spring sliders? http://www.liquidironindustries.com/product.php?productid=17611

 

·
Registered
Joined
·
27,625 Posts
Discussion Starter · #2 ·
Rear axle:
-Shackle orientation (standard, inverted, tension)?
-Shackle length?
-Sliders? (yeah my curiosity has been peaked)

I will add and edit tomorrow, but that's it for the night
 

·
Registered
Joined
·
27,625 Posts
Discussion Starter · #4 · (Edited)
Front axle, shackle in front. I'm hoping someone with actual knowledge and tech can chime in as well. I'm just going off of what I've done and found researching, no quantified data per se.

Benefits:
-Possible to build lower
-Front axle moves forward during compression (firewall clearance)
-Most can use a standard slip driveline, not long travel
-On a climb the tires are directly pulling at the chassis due to the fixed location of the spring

Cons:
-For years people have been doing shackle reversals claiming better stability and road manners. Is this really true, or were there other problems with the suspension (worn bushings, poorly designed parts, too long of a shackle, bad geometry)?
-It could be argued the ride may be harsher in the rough stuff at speed due to the axle having to move forward. I will argue that this motion is no different than a 3 or 4 linked axle and those make up the current majority of "go fast" 4wd's.

I did a lot of researching before I built my first front shackle rig. I was mostly curious about where the shackle should be in relation to the spring eyes. I found a reference to the shackle mounting point being better if above the fixed spring eye elevation. IIRC it had something to do with roll axis angle, which would affect road handling characteristics. In any event this idea also went along with some OEM applications, primarily a leaf sprung super duty. The shackle is mounted very high up on the chassis, with the fixed spring eye sitting on the bottom of the frame, at a much lower portion of the frame.
(I'll have to add a picture later)

I've now built two rigs with a front shackle design. The first was the 4skinner build: http://www.pirate4x4.com/forum/showthread.php?t=1003306 I traded this off as a rolling chassis, but am still friends with the owner and he has been happy with how it works/ handles. This rig has seen trail use for about 5 years now, very limited street/ highway time.

Frame Mount:


Shackle and mounts:


 

·
Registered
Joined
·
178 Posts
I dug up this thread while researching leaf springs/vehicle dynamics.
I thought I would add this link I found on the subject.
RPM Net Tech Articles: Leaf Springs - Powered by: AFCO

Leaf springs have been used in dirt track racing forever so if people are interested in more hardcore tech like roll center height, and how that can effect things like roll center migration, chassis roll rate and cool things like that, I would look there.
 

·
Registered
Joined
·
111 Posts
Good thread, I'm staying tuned.

So if front shackles are superior, why does my Toyota have rear shackles, and should I change them?
 

·
Premium Member
Joined
·
29,255 Posts
Good thread, I'm staying tuned.

So if front shackles are superior, why does my Toyota have rear shackles, and should I change them?
I'd say that if what you have currently works for you then no, there wouldn't be much gained by swapping them around unless you are redoing everything anyways.

Rear shackle gives a bit more lift, hence why so many run shackle reversals on vehicles equipped with front shackles (jeeps, IH, etc.)

100 ways to skin a cat, that is like asking why GM doesn't use drop out diffs and toyota does.
 

·
Registered
Joined
·
537 Posts
I'd say that if what you have currently works for you then no, there wouldn't be much gained by swapping them around unless you are redoing everything anyways.

Rear shackle gives a bit more lift, hence why so many run shackle reversals on vehicles equipped with front shackles (jeeps, IH, etc.)

100 ways to skin a cat, that is like asking why GM doesn't use drop out diffs and toyota does.
Great thread I will be watching.
From what I have read the reason so many jeeps, IH, ect. run a shackle reversal is more to keep from bending the springs.
When you come up on a large rock, rock ledge ect., the first thing that is going to come in contact is your leaf spring/shackle. (shackle forward) In order to get over it you have to give it some power. Hopefully it will climb and not bend your springs.
I run shackle up front (Jeep YJ) and this has always worried me.
Sliders would be a good alternative to a shackle reverse and would help bring the rig down some but I would think you would also have to extend the front end out some.
Anyone have some close up shots of rigs running sliders and can they be run with military wrapped springs?
 

·
Registered
Joined
·
2,588 Posts
I run a 6" shackle reversal up front with my 52's in my buggy. Having said that, I'm still working on a skid plate to go from my bumper down, and to my motor crossmember. The idea is to make it relatively easy to install/remove for when the weekend situation calls for needing it.

Hows everyone doing with their box sliders? I see someone earlier asked how they were holding up on DD's. Im kinda curious as well since I would have to be able to run these at high speeds, as well as let them fully droop when I have front end lift.
 

·
Registered
Joined
·
8,917 Posts
That link has some good info in it. I was with a guy one time that had shackles up front, he drove right up to a rock and the shackle hit the rock, he tried to climb the rock and before I could get the word "STOP" out it bent the main leaf right back. Took us a while to bend it back to where he could drive. I am sure the leaf didnt last long after. I would like to see what the benefit for having shackles up front are.
 

·
"All Weeee Drive!"
Joined
·
12,032 Posts
I've got 4-5 trips on my sliders: 56" Ford F150 springs, slider toward the rear on front springs.

So far, I like the way they flex/perform.

However, 2 things bother me: They are noisy... The springs will grind/slide on the inside of the slider (metal on metal), as well as shift from side to side making loud "clanking" noises. I added a poly spacer before last trip (round, the size of a silver dollar). It helped, but I think it needs to be larger to keep the partial wrap secondary spring from rubbing.

Second, I think I already bent my sliders (from landing on rocks).... I'll snap some pictures one day this week. (don't get me wrong, they are beefy, my rig is just heavy).

Here is some poser/flex shots... (note, my front DS was too short, so I moved the springs back 1 notch in the adjustable hangers).

 

·
Premium Member
Joined
·
29,255 Posts
TOYOTAPARTS:21161082 said:
That link has some good info in it. I was with a guy one time that had shackles up front, he drove right up to a rock and the shackle hit the rock, he tried to climb the rock and before I could get the word "STOP" out it bent the main leaf right back. Took us a while to bend it back to where he could drive. I am sure the leaf didnt last long after. I would like to see what the benefit for having shackles up front are.
Hopefully within the next year i am going to be hacking up my rig a ton, figured id give front shackles a try as well. Mostly trying to keep my front end from unloading on steep climbs. Currently it does pretty good too a certain point. Going to also add a front traction/ladder bar and that is easier to do on the mounted side instead of shackles side.

Running second gen ruf pack so the approach angle is pretty good, hopefully adding a bumper/winch mount Will give something to catch before the springs hit the rocks.

Also, with a ruf back and offset center pin, running the long side as the mounted side and short side shackled should (in theory at least) give better flex with same spring rate as the mounted side is more or less the link or radius arm and the shackled side is more of spring rate and control.

I plan on getting rid of the chevy rear and running backwards third gen rears, the long side is close to the same so should get similar flex but a shorter short side should help with departure angle.

I will update when that happens though, still need to get moved before i start anything :laughing:


Edit: mike, absolutely interested in your pictures on how they jammed.
 

·
Registered
Joined
·
1,847 Posts
Military wraps and spring clamps, that's my biggest advice on leaf springs.

If you look at OE vehicles that ran shackles up front, most are of an older design, scouts, jeeps, cruisers etc. The slightly newer trucks, like chevys and Toyotas, have the shackles in the rear.

My guess is that the jeep designers went for a forward shackle because of packaging, limited ground vehicle suspension design knowledge(not their fault, they just didn't have the knowledge base that we have today), and the fact that these vehicles weren't meant for high speeds or rockcrawling back then. Other companies like Toyota copied them and made cruisers, and everything worked fine for awhile.

Chevy with a bit more knowledge now redesigned things and put the shackle in the back and that worked even better now that highway speeds were higher. Latter Toyota copied that too and the steering and made the minitruck.:D

Of course who knows what ford was thinking with the superduty, they fixed that though in 05 and went coils.

There are tradeoffs with each, shackles in front or back, but I believe either will work just fine if correctly set up. Like everything else we do, you have to have a good setup and geometry for it to drive down the highway at 70mph without killing a busload of nuns and still reliable crawl over rocks.

The sliders interest me. Most I've seen are mounted horizontaly under the frame rails. Would there be any advantage to mounting them at an angle under the frame? Could having them angled keep u-joint angles in check possibly or is there some other gain in the geometry of the system?

Kevo
 

·
Registered
Joined
·
1,847 Posts
Another thing to think about when thinking about leafs pushing or pulling on an axle.

In 4wd that front axle is actually pulling the rig along. Most people look at suspensions as if the vehicle is pushing the axles along, in reality its the axles pulling the vehicle along. Well, at least until you break something.:D

So shackles in the front would have the front axle pulling on the leafs to move the rig, and shackles in the back would technicly be pushing on the leafs to move the rig.

The earlier example of the shackles in front jeep pushing the front end into the boulder is somewhat wrong. That front end, if its working, is actually pulling the body along with it as it goes in, up and over.

Kevo
 

·
Premium Member
Joined
·
29,255 Posts
Kevo: from reading a few different articles and links from the circle track and car guys the consensus is that the 'proper' angle for the Sliders is to be pointed at the solid mount eye. As in, if you draw your line between the spring eyes, your Sliders should follow that line for smooth operation.
 

·
"All Weeee Drive!"
Joined
·
12,032 Posts
Kevo: from reading a few different articles and links from the circle track and car guys the consensus is that the 'proper' angle for the Sliders is to be pointed at the solid mount eye. As in, if you draw your line between the spring eyes, your Sliders should follow that line for smooth operation.
This has been discussed a lot on PBB...

http://www.pirate4x4.com/forum/jeep-hardcore-tech/652426-sliders-versus-shackles.html


http://www.pirate4x4.com/forum/international-harvester/1090594-80-800-shackle-reversal.html
 

·
Premium Member
Joined
·
29,255 Posts
good links, thanks.

question for you mike from your second thread.

My biggest issue has been hitting my front shackle on a rock, which in tern forces the shackle to invert/bend the spring... It's happened about 3-4 times in the last 2 years & I'm tired of it.
Just want to be clear as I toss this stuff around in my head, were you running clamps on your springs? seems like keeping them from inverting could be straightforward enough, though I have inverted my rear shackled fronts (stock toy) before, I have never had that issue when backing up into objects where the rear suspension acts essentially as a front shackle setup.


3-4 times in a couple years sounds like a bunch to be replacing springs, but I don't really want to spend a couple hundred bucks going to links :laughing:
 
1 - 20 of 32 Posts
Top