I run the shackle in the back. Maybe its because GM puts them that way or because I used to run off road vehicles and the first thing we always did when we snagged a jeep was move the shackles to the back to take some of the dodgyness out of them. Anyway they handle better with the shackle in the back. But a lot of these fellas are going to tell you the other way around.
Up until 36 , Chevy trucks had the shakle in the front and the spring eye anchored in the rear. In 37 they flipped it around , dont know why. I dont know if it really makes a difference, I would be curious to hear. Mitch.
Mitch, The way it was explained to me was that with the shackle in the front when you hit a bump it affects you caster adjustment in a negative way. With the shackle in the rear it squishes in a different direction. I do know it makes all the difference in the world on a Jeep CJ. Perhaps the difference isn't as noticable on a longer wheelbase vehicle but if it handles better a certain way and you are building it anyway why not build it the way that it handles best.
Randy, after talking with Adam about this on the '49, we decided the shackle in the rear is often a better idea because of how the spring flexes. The force from hitting a bump in the road is up and toward the rear. With your pivot point in the front, it puts much of the stress on the solid mount in the rear and provides very little flex from the shackle. The F-1 has shackles in the front which is why I asked him about it... We decided when I get the new springs and lowered axle we are going to look into putting the mounts in the front and the shackles in the rear. The steering setup allows for movement so stock pieces should work.
Think like this.. - When the long end of the spring is "pushed on", the spring can wind up into all kinds of strange shapes and do all kinds of ugly things to the oveall length of the spring, thus moving the axle all over the place. When the spring is "pulled on", it'll go up and down from two loads. One load is purely, up and down, the other is from the possible changing in the arch, which is a lot less of an actual movement in the axle. By far the better/safer way to go is solid in the front and shackle in the back. Mike
It was explained to me to be better with the fixed mount at the rear, and shackles at the front! That was how I did my Pop (Anglia) back in the '80s, based on the Hot Rod New Angle Anglia chassis build-up, I think. I believe it is to do with the steering, especially if you have a side-steer setup, and also the caster, as porknbeaner said. Anchored at the rear is more like a four-bar or wishbone setup, so the arc of travel would better match the drag link arc. Plenty of Ford pickups came that way from the factory, so I guess there must be something in it.
Steering has a big part in the shackle location. The shackles should be on the opposite of the steering gear. If the drag link runs forward from the box to the axle, the shackles should be out front. If the drag link runs from the front of the frame back to the axle the shackles should be at the rear of the springs. I think the same applies for cross steering as well putting the more solid non shackled mount closest to the steering gear/steering link.
Stock setup on my '60 F100, and on a '91 Jeep Wrangler, was shackle in the front. Never had any handling trouble with either, even after the F100 was lowered. I think something other than (or in addition to) shackle location causes handling problems for people.
The shackle position has an effect on the steer of the car. This is compounded if you are using a side steer car as the swing of the steering drag link changes as the load/arc on the spring changes. The position of the shackles should be based upon the major intended use of the car, long distance road, street - strip or full race. If you check various early beam axle automotive design you will see that the shackle position varies. It appears to be based upon the desired characteristics of the vehicles handling over contoured roads, the arc of the spring for soft ride and the steer effect as the suspension moves during spring load. To complicate your decision also remember that the direction of roll of the anchored spring eye, up or down, will also have a slight effect on the amount of spring movement imparted to the axle during load or unload condition. Of utmost importance is not to build a design where the axle center line wallows fore and aft as the spring flexes. This creates a tracking nightmare at the steering wheel. Assuming you are building a gasser style car the shackle position to the front may be your better choice, as the axle position with a fixed rear mount remains more constant as the front end rises on acceleration and returns to ride ride height.
My understanding is that the rear spring should be solid on the front, and the front spring should be solid on the rear. This is so that when you turn the flattening of the spring increases the distance between axles slightly, and helps the car corner. Of course mud boggers or anything that's been drasticly changed may not apply to this effect.
If the shackle breaks or comes loose, the natural reaction would be to step on the brakes. If it is on the front, the spring becomes a pole vault. If it's on the rear, the spring just hits the bottom of the frame and nothing really bad happens.
The distance from the spring eyes to the axle is different. Shackle at front or rear don't matter as long as the anchored end of the spring is the short end(axle to spring eye).
do a SEARCH this has been covered many times before,mines in front has been for 35 years,works great........why over think it
No one is overthinking it at all. He asked a question and it was answered. So you have a car that has had the shackle in the front for a long time. If you moved the shackle to the back you would notice a marked difference. Does that mean that I think you should move yours to the back? Not really if you're happy with the way that it handles leave it the way that it is.
I just can't get past that fact.I know Dick Spardo has forgotten more about suspension design than most of us will ever know, and all the complicated stuff about handling and geometry, etc., and that's all god on a silky smooth drag strip, but if the car is going to be used on the street, it just seems sht shackle in front is wrong, from a stress point of view. But smarter people than me(Jeep and Ford engineers) do it that way, so it is what it is.
I bought an axle and springs from speedway motors. Their instructions (on line pdf) said to put shackle to the rear. From what i understand a front mount can flip over under certain circumstances and cause a real caster issue. The rear mount can not flip over... I put mine to the rear.
Every big truck on the road today has them on the rear. Most also have the steering box out front too. Doesn't seem right, but there ya are! It would seem to make sense to have the more solid mount on the end where the steering comes from. That way the axle movement won't cause bump steer.
I guess mine is all wrong by what i'm reading from everyone. .... But why does it ride so well and drive so nice. Should i follow all these remedees and MAKE IT RIGHT?? or just bang gears and keep grinnin.
Bang them gears!!!!!!!!! I'm going with them in front. No good reason, it just feels right. And Stone, Woods and Cook did it so that's good enough for me!
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