Cutting stock springs....Q's inside

Peckaldee · 01-27-2002, 11:18 PM

Have any of you guys ever experimented with cutting the stock springs? If so, how much to achieve a 1" to a 1 1/4th drop?

I've always heard that it's not recommended to cut the stock springs. But they are linear so it shouldn't matter if some of the turn is taken off. This shouldn't be done on progressive springs but the stock linear's should be ok.

I'm going to be installing new swaybars very soon and would have a chance to do this while the car is in the air. Although I'll be going to the Eibachs in less than a year, I was wondering if I could get away with it for the time being.

I'd like to see some different speculation on this. Thanx

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Justin Peck
95 Z28 A4 w/ 3.42's, some mods

273 RWHP, 308 ft-lbs RWTQ w/ HPP tuning(now running LT1_Edit)

Best time - 13.50 at 103.21

Pecks Z - Website of the Ride!

Dr.Mudge · 01-28-2002, 02:57 AM

I haven't cut the springs, but if you do just make an estimation that you want to cut 1/2 coil or 3/4 etc.

Make sure you dont heat the spring up while you do it, not sure how hot it would get from friction of the cutting wheel (dont think blade would do the job easily), but excessive heat would destroy the springs rate, making it softer (without retreating it).

I wouldn't cut too much, while the rate will increase some I dont think it would be stiff enough to have a safe, very low car, so I think you wouldn't want to cut off much.

Norm Peterson · 01-28-2002, 08:17 AM

I have cut springs before. Loss of temper over 1/4 of a coil isn't going to be a problem - that much sits on the spring seat anyway and can't go anywhere, can't flex, can't sag, can't break.

They can be cut with acetylene if you're quick about it. It's when you don't have enough heat to get the cut to start that you begin to have heat travel problems. For a little insurance against heat traveling along the spring, lay the spring on its side in a tank containing a couple of inches of water.

If you're really concerned, get a carbide blade for a hand hacksaw. Those things can cut almost anything and you have complete control of how much heat is being added to the spring.

Norm

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1979 Malibu, 355, 5 speed, cornering tweaks, some other stuff
2001 20th Anniversary Maxima, 5 speed

[This message has been edited by Norm Peterson (edited January 28, 2002).]

Peckaldee · 01-28-2002, 11:32 PM

OK, heat shouldn't be a problem. We'll be using a metal cutting wheel that we use to cut inch thick steel all the time. I'll just make sure to water it down really well.

Now, how much should I take off to achieve this 1" drop or a little more. Nothing more than 1.5" though.

Dr.Mudge · 01-29-2002, 01:07 PM

Measure the total length, count the # of coils. I'd probably start with 1/2 a coil though and see how it works, although if you count it you would be closer to 'getting it right' the first time without constant assembly/dissasembly.

Peckaldee · 01-29-2002, 03:13 PM

I talked to a buddy of mine today that is cutting the springs on his 97 SS. He seems like he's going low. Taking 2" off the back and 1.5" off the front. I may do close to the same but I'm gonna want the front end to be slightly higher than the rear. So how does 1.5" front and 1" rear sound to you guys?

Dr.Mudge · 01-29-2002, 07:45 PM

The weight is pointed towards the front to keep the car turning well in corners, not sure that the opposite would be a good idea.

How about a balanced cut front to back then?

JordonMusser · 01-29-2002, 09:45 PM

I think you are confused how a spring works

even as a linier rate spring, removing a coil is going to make the spring quite a bit stiffer.

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-94 Black T-Topped Z28 M6, 10s, and daily driven!
-96 CBR F3, modded of course
-92 Talon Tsi AWD, also too many mods..
-99 Tony Kart

http://www.fastblackcar.com

Peckaldee · 01-30-2002, 05:25 PM

Jordon,

This could be true but I don't see how it would get stiffer? You would have less travel but just cutting some off isn't going to change the rate of the spring. All cutting will do is leave you with less spring and a lower car.

V6Bob · 01-30-2002, 07:16 PM

Here's why it's stiffer. A coil spring is just a torsion bar wrapped in a spiral.

Take two torsion bars of the same diameter steel, one long and one short. Twist them at the ends. The short one is harder to twist, less leverage. So the shorter coil spring is stiffer in lbs/inch.

Math version: Spring rate is:

K = G X(d, to the 4th power) / 64n X(r, cubed)

G is a constant (depends on the spring material), d is diameter, r is radius, and n is the number of coils. Cut the spring, n goes down, spring rate goes up.

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2000 Firebird convert, chameleon/tan, M5, Y87, TCS
KBDDs, BMR STB and Panhard, 245/50-16 GSCs

[This message has been edited by V6Bob (edited January 30, 2002).]

Dr.Mudge · 01-31-2002, 05:52 PM

Here is a 'trick' from "How to Make Your Car Handle".

They put a coil spring compressor on the spring, compress it a 'bit', and put it in an oven at 400ºF for a 'few minutes'. Take it out and compare measurement to before and see if its sufficient.

Not sure how adviseable this is, but they seem to imply this will not destroy the rate as a torch would.

n = number of active coils, or free coils + 1/2 coil

[This message has been edited by Dr.Mudge (edited January 31, 2002).]

JordonMusser · 02-01-2002, 09:28 AM

what V6Bob said

in the simplist terms, its a torsion bar in a coil...

------------------
-94 Black T-Topped Z28 M6, 10s, and daily driven!
-96 CBR F3, modded of course
-92 Talon Tsi AWD, also too many mods..
-99 Tony Kart

http://www.fastblackcar.com

Steve in Seattle · 09-02-2002, 06:00 PM

Just a quick clarification, a torch does nothing to a springs k-value (spring rate). The k-value is determined by the physical dimentions of the spring, and the material its made of. Heating the spring improperly can lead to decreased spring load, where the spring "sets" with a lower coil length; making it sag a bit lower. But the spring rate remains the same (it just has less travel left).

Cutting and removing a length of coil DOES change the rate as stated above.

(I know this was a pretty old thread, but I wsa doing a search and thought it might be useful) I belive the trick in how to mark your car handle was actually an attempt to retain the stock spring rate, but to lower the car an inch or so.

(but I'll have to check to make sure)

Dr.Mudge · 09-04-2002, 01:37 PM

Wow, yes this is an old one... I wouldn't cut the stock springs that much though, ouch