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Rear Spring Shackles

Started by JimNolan, 2017-08-07 10:27

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JimNolan

   Need some help here guys. My 57 Fairlane 500 has drooped about 1" since I put new springs on it about 8 years ago. I guess drag racing etc hasn't helped any either. You used to see the whole wheel when looking at it straight on and now it's about an inch lower than that. If I flip the shackles it'll be too high, I know that. And, air shocks etc is out of the question.
The spring shackles that we use are shackles that the pins are 2 1/2" apart and the spring is on top of the spring mount, not under it like a flipped shackle would be.
   MY QUESTION:  Has anyone used a shackle that has 1 1/2" pin spacing, and if so what was the results. I just ordered a set two days ago and they'll be here tomorrow. I measured my spring shackle this morning and I've got about 1 1/8" space between the spring eye and the mounting eye. So that would put the spring pretty well on top of the mounting eye.
Thanks guys.
If there are no dogs in Heaven, then when I die I want to go where they went.

John Palmer

#1
Jim, I think new springs normally "take a set", or "settle" after they have been used for a while.  You might be able to get your inch back with the shackles, but remember that you will only change the ride height by one half the amount of the change in the difference of the rear shackles.  This is because you still have the stationary end of the spring mounted to the frame.

For about a hundred bucks, any local Spring Shop will re-arch your springs.  Just tell them exactly how much of a change you desire.

We used to drag race a rear leaf spring Falcon.  We ran it with an "open" differential.  To get the car to launch with equal traction on each slick we used a much stiffer spring only on the side that would unload during launch.  You have a great deal of "tune-ability" racing with leaf springs, and they don't always have to be the same from side to side. 

JimNolan

#2
Thanks John
I would like to add this. By reducing the pin spacing on the shackle I should also change the spring rate of the spring. By shortening the shackle pin spacing I should be limiting the length the spring would go to flatten out. To put that into prospective, when drag racing with slicks I put the drive shaft into the body of the car (I wasn't using a snubber on the differential, after that I bought a snubber and put on the differential). Point is, the spring should regain some of the arch it had by preventing it from flattening out as much.
If there are no dogs in Heaven, then when I die I want to go where they went.

John Palmer

#3
Using a good quality "compression and rebound" adjustable shock designed for the weight of your car is also a very good investment for drag racing.  The shock needs to be able to control the axle movement during the point of weight transfer.  The springs should be able to support the cars weight during the launch, and the shock controls the rate the spring moves.  At no point should the weight be supported by "bottoming out" on the snubber's.  A cheap way to measure the amount of suspension travel during the launch is to install "zip ties" on the shock shafts.  Then you can measure how far they are pushed up the shafts, after the run.  Bottoming out on the snubber's, is the magic point when parts start breaking, has been my experience.

What do you use for traction bars?

If your chasing big ET improvement, it's all going to come in the first 60 feet.  It really does not take huge tires, the "small tire radial guys" have set some incredible ET's on small, and DOT tires.  It's all about controlling the movement, and weight transfer.

These suggestions come from 19 years of track time wrenching on my sons car.  Our last run was a 1.50 60 foot, and a 10.60 ET, at 132 MPH running on 145 cubic inches at 8000 RPM.  The car/driver weight was 2000#, running 280 HP at the crank, and an additional 70 HP shot of NOS.  This was all done on a 6" wide M&H tire.

JimNolan

John, the drag racing is moot now. I took out the 375 hp engine and put a little 390 with 325 hp in it last year and haven't spun the wheels so far. I have Traction Masters old style traction bars on it. The fact it doesn't wheel hop and break axle's like it did before speaks volume's for the traction bars. But, the racing is over with and ride and stance is what I'm looking for now. I run the 1956 stock Fairlane shocks on the back. I'm not a big fan of the shocks putting much of a load on their frame mounts. Those mounts were flimsy at best in 1957.
If there are no dogs in Heaven, then when I die I want to go where they went.

JimNolan

UPDATE: The spring shackles that were 1 1/2" from pin to pin didn't work. They needed about a 2" span to get them on. I got tired of fighting it and just put the original shackles back on it. Between thinking I'd broke the flexible brake line going to the rear end and having traction bars that limited movement of the springs, I just gave up. Rear fender will just have to hang below the top of the wheel rim. I'll just tell everyone it's a low rider. lol
If there are no dogs in Heaven, then when I die I want to go where they went.

geraldchainsaw

Jim,  your right about the shock supports,  both of mine have been reworked.    i changed orig shocks to a higher or longer stroke just so i could get the wheels off when i get a flat

JPotter57

Low rider?  Your 57 probably sits higher than when it was new, lol.  Trust me Jim, your car looks great as it is...
1957 Ford Custom 427 2x4 4 spd
Old, loud, and fast.