Ok, so this has just been bugging me recently - why do jeep wranglers have the shackles in front on the front leafs, and yotas on the back of the front leafs? what's the advantages/disadvantages, and how come they're different?

Shackle in the rear gives a better ride on road. Shackle in the front pushes the wheel forward and into obstacles under flex. I believe there is axle wrap or pinion angle issues when switching front to rear (can't remember).

yeah there is big pinion angle issues on most cars when you do a "shackle reversal" but it makes a huge difference to how a car goes over obsticals because the spring bounces backwards and helps you over rather than bouncing forwards and hindering forward travel. also means you dont have shackles as the furtherest forward part of the car to hit everything you try and drive over

yeah there is big pinion angle issues on most cars when you do a "shackle reversal" but it makes a huge difference to how a car goes over obsticals because the spring bounces backwards and helps you over rather than bouncing forwards and hindering forward travel. also means you dont have shackles as the furtherest forward part of the car to hit everything you try and drive over

First off, we`re not talking about cars. Second, you have your explanation backwards. With shackles forward, your front axle pushes into the obstacle giving better traction to get over, having shackles in the rear lets the axle push away limiting traction. The are many pro`s and con`s for both. If your rig is a daily driver, shackles to the rear make a big difference in handling and ride quality (good). Shackles to the rear can mean alot of nose dive while braking (not good). Shackles forward mean more traction on the trail in theory (good). Shackles forward mean a better chance for spring damage when they hit something (bad). My take, I run shackles reversed because my rig is a DD. I personaly don`t feel it suffers offroad because of that.

I have seen plenty of rigs both ways and I have never seen one be of a specific advantage on the trail. Forward shackles won't give you more traction....spring rates are spring rates....they will just be more efficient. I know, I know...I've read all the theory on the stuff, but ultimately I think vehicles are just designed one way or the other out of convenience to the manufacturer given chassis specifics. I will contend that shackles in the back does ride better due to a more ideal suspension reaction angle, but unless that's super important to you I wouldn't worry too much about if your shackles are in front.

I agree with the way the vehicle was engineered. But on the trail I have seen up close both a Yota and an YJ. the Yota has a tendency to steer off the obsticle with the front axle when you flex onto it. The Jeep turns into the obsticle during flex. Shackle reversal will create a driveline angle problems, but that is fixable with wedges or changing the spring pirch on the axle. I personally like the jeep style shackles, but I prefer the wheelbase and easy parts of a Yota.

i was just wondering as i read the post.....for you guys that do run SR what is the angle of your rear shackles with full weight.. and what springs...are the shackles just about up and down or are they back slightly....on my cj i run 2.5 yj SOA and have my shacles about 45* back.. so when i wheel, i get some uptravel, but a lot of downtravel and i run some bumpstopps so i can only go up about 4 inches.. i am a member and the search on here really blows so anything can help...i know my jeep drops the front end when i slam the brakes..but i dont drive down the road often and its not that bad but does that shackle angle matter that much as far as street driving..let me know..thanks

MY front shackle angle is a little more vertical than yours mostly because of my really long front springs and the frame shape. Even with widebody boomerang shackles I still had to watch out for frame contact during up travel so mine aren't quite ideal, but they aren't the limiting factor right now either. My rear shackles do sit at a 45 degree angle though and I really like it for the equal up and down travel.

hey, andy, did you get your shocks to stay on the rear axle yet?

Shocks are over rated. I'd just like to keep my motor in one piece. Shocks won't do me much good with a motor in pieces again and you know that.

I run shackles to the rear in my cjunk, my buddy has his shackles in front and has had way more spring damage.

The reason for shackle placement either front or rear is dependant upon spring arch. On a YJ, the stock springs are pretty much flat, so any movement up or down is going to shorten the distance between the axle mount and the rear spring mount moving the axle to the rear when it encounters a bump. This makes for a better ride on the road. The Toy has some arch to the spring, so when the axle travels up, the distance between the spring mount and axle mount increases moving the axle rearward, again for a better ride.

Cliffnotes: If you are running an arched spring, moving the shackle to the rear can improve the on road ride, if your running flat springs, keep the shackle forward.

There is little mystery to suspension design, its all geometry, look at it for a bit, and it will all make sense.

http://www.jeeptech.com/susp/elkcahs/nonr2s.jpg
http://www.jeeptech.com/susp/elkcahs/rev3s.jpg
http://www.jeeptech.com/susp/elkcahs/narch1s.jpg
http://www.jeeptech.com/susp/elkcahs/rarch2s.jpg

wow kwrangln is one of the few ppl that understand why some vehicles have front shackles. Any vehicle that came with front shackles had either flat or negative arch leaves stock.

But what came first...the flat springs or the forward shackles? It all goes back to whatever was most convenient for the engineers at the time I think. I mean you could say the same of spring over versus spring under setups. Spring unders have more steeply arched springs than spring overs, but what came first...the spring design or the axle attchment design?

But what came first...the flat springs or the forward shackles? It all goes back to whatever was most convenient for the engineers at the time I think. I mean you could say the same of spring over versus spring under setups. Spring unders have more steeply arched springs than spring overs, but what came first...the spring design or the axle attchment design?

Not entirely sure what you're trying to prove, I explained why shackles are placed where they are from the factory, now you want to know what came first? Does it matter?

What actually came first, was NO shackles. Early horse drawn carrages used fully eliptic springs. Picture two leaf springs, one on top of the other joined at the eyes.

Then came transverse leaf springs with the center joined to the frame and a shackle at each end attached to the axle.

Sometime in the 1920's longitudinal leaf springs like we are used to seeing became pretty much standard with the shackles placed for the best ride and handling. Flat spring, front mounted shackle, arched spring, rear mounted shackle. Most springs from the factory are pretty flat, since they tend to ride better in the first place.

Ride and handling are but a small portion of suspension design, you also have to take into account ride height, load carrying ability, intrusion into the passenger compartment, and overall packaging.

You're wondering about the methodology of suspension building that has been understood for almost 100 years, who cares what came first, you're not going to change physics and geometry.

If you're going to try to convince anyone that the manufacturers just put the shackles wherever they fit the best, then you're mistaken and a fool.

intrusion into the passenger compartment, and overall packaging.


If you're going to try to convince anyone that the manufacturers just put the shackles wherever they fit the best, then you're mistaken and a fool.

Don't you contradict yourself right there? :flipoff2: Seriously...I'm not trying to get into a pissing match at all. I understand plenty about suspension design and spring design. I also understand that a huge part of manufacturing from an engineering perspective is compromise for price, space, ease of manufacturer, whatever and I think that that probably has more to do with why the manufacturers chose to put the shackles like they did. With the constraints on frame design, ride height, wheelbase, and yes....even ride quality....I think Jeep just found it best to have the shackles in the front while Toyota went with them in the back. I don't think one design is any better than the other. Both have advantages and disadvantages but ultimately were chosen for their perspective positions by a whole slew of things, much of which probably wasn't directly "suspension related."

I could possibly buy into that if Jeep hadn't produced a model with a shackle reversal from the factory (50's M38A1), and then went back to their standard setup. There are enough people running a shackle reversal on jeeps for whatever reason to prove it is'nt complicated, or hard to accomplish within the design constraints of the frame package, so we're left with design to optimize the factory suspension design.

I run shackle foreward on my explorer and it flexes well, but my main problem is the axle pushes back and sometimes flips the shackles over and it gets bad wrap which caused me to shear my pinion the other day.

Moved mine to the rear on almost flat springs, rides better and straighter, takes bumps better but softened up the suspension when hitting whoops at speed and required more shock relocating bumpstops, long travel driveshaft, and degree shims.... I bored holes through the frame and welded in pipe for the top of the shackle so it doesnt hang down very low below the frame, shackles sit about straight up and down at ride height.......... I am happy with it and wouldnt go back, it nose dives when braking, but its a trail rig not a daily driver.

What does the frame look like where your shackles are mounted? My shackles are mounted at a point where the frame is bowing in, bending down, and right where a body mount ties in. Talk about a pain in the ass....Wide body boomerang shackles help keep things aligned, but it just wasn't going to work to run shackles in the front without shorter front springs.