Cutting Coil Springs

[horseplay]

I have been thinking about trying this.
I was going to start with a 1/4 a coil cut.
I am looking to get a just a lil lower stance.

My question is doesn't this effect the load rating of the spring (lbs/in) which would be a nice plus for me too.
Is there any formula for this?

[gotstang]

Yes, cutting coil springs affects the stiffness; I've seen several formulas for this and only a few seem to work out right. Wire diameter, # of turns, and height all factor into the load rating. Eaton Detroit has one formula somehwhere on their website and their example is a 67GT spring, so it's pretty useful for us Mustang guys.

Right at the moment, I'm cutting a set of 67 springs to fit in my 66; I'm taking them down to the same height as the originals, then I'll probably cut at least 1/4 of a coil.

Now if I could just find my saw...

[deuce68]

gotstang I cut my front springs and used a die grinder with a flat cutoff disc.

[shelbyman1]

Originally Posted by deuce68

gotstang I cut my front springs and used a die grinder with a flat cutoff disc.

In my opinion the easiest and best way.

[gotstang]

Originally Posted by shelbyman1

In my opinion the easiest and best way.

I agree. Worked like a charm when I did it a few days ago, though I might use the bandsaw to true them up.

[shelbyman1]

Originally Posted by gotstang

I agree. Worked like a charm when I did it a few days ago, though I might use the bandsaw to true them up.

Have found the best way to clean them up is to use an angle die grinder with an abrasive pad.

[mikes69mach1]

I cut 1/2 coil off my Mach with a cut off tool without even removing them from the car. I did take the load off the front tires tho.

[autoxsteve]

I use a hacksaw and take it slow.....

Works fine and it does affect (decrease) spring tension.

[supershifter2]

use a grinder or a saw do not use a torch and dont knick the coils as that will cause a breakage.

[gfmccann-temp]

Originally Posted by autoxsteve

.....Works fine and it does affect (decrease) spring tension.

You're saying cutting the spring DECREASES the tension? In fact the net spring rate will increase. A spring is simply a rolled up steel bar that twists as the spring is compressed. Try twisting a yard stick a quarter turn. Now slide your hand in a foot (= cutting a spring) and try to twist the same rotation... Not so easy.

[supershifter2]

Originally Posted by gfmccann-temp

You're saying cutting the spring DECREASES the tension? In fact the net spring rate will increase. A spring is simply a rolled up steel bar that twists as the spring is compressed. Try twisting a yard stick a quarter turn. Now slide your hand in a foot (= cutting a spring) and try to twist the same rotation... Not so easy.

i 2nd your post ! cutting a coil increases tension. the 620 springs i used back in the early 70's were boss 302 springs that had ( 1-1/2 coils i dont remember exactly ) cut off and that raised the rate to 620 and lowered the car a little bit. i bought mine from MAIER Racing back in the 1970's. i think this was taken from the the boss 302 chassis manual. anytime you remove coils from a spring it becomes stiffer and also lowers the car a tad.

[FredG]

Horseplay,
I found the quickest way to cut the springs was with a cut-off wheel. Then I put a dab of paint on the cut end to prevent rust....For what it's worth, though don't let the advertised spring numbers, like 620 (since that seems to be a popular number) fool you, as I found that that, at least in my experience, it had nothing to with the actual spring rate...might have been the gauge of the wire or something, but all I know is that I wanted a 600 pound front spring rate in my 65 and ordered "620's" from NPD, then Mustangs Unlimmited, and then CJ's. All three sets didn't come close to "620" pounds with the NPD's measuring 495 and 505! The other two were in the low 500's. Wound up calling Scottie at Cobra Automotive and ordered a set of 67 and up big blocks, cut off approx 1 1/2 coils and then brought them over to a local roundy-round race shop (prob the only one on Long Island) for measuring on the spring gauge...605 and 610 pounds!

[DIRTY289]

Originally Posted by gotstang

I agree. Worked like a charm when I did it a few days ago, though I might use the bandsaw to true them up.

If you have a bandsaw at your disposal, wouldn't that be the best tool to cut a spring?

Thanks... Bruce