Overhauling Cut Springs

[RUS777]

I was watching the OVERHAULING last night on Military channel where they were overhauling veterans rides.

Anyways the episode with the 1968 Pontiac Firebird which was painted black. Chip Foose went on and designed this custom suspention and frame for the car, and @ the end, being unsatisfied with how the front sits, he decided to lower the front of the car. He simply took front springs off and CUT THEM?!?!?

I always knew that cutting springs is a "no go" and seeing it done by one of the leading custom car manufacturers was seriously jaw dropping.

Am I the only one who is surprised to see that? What do you guys think?




Here is a pic of the CAR:

[californium90]

yes i saw that too. i dont have very much knowledge about suspension systems but i guess whatever chip decides goes ?

[RUS777]

Originally Posted by californium90

yes i saw that too. i dont have very much knowledge about suspension systems but i guess whatever chip decides goes ?

Yeah, but I do not think it is safe.

Springs are designed for a certain rebound rate, and cutting them probably messes it up.

[RTexasF]

I saw that episode and thought it odd also. It was like "We're outa time, do whatever".

[RUS777]

I do not know, I was thinking that there is an explanation out there that I am not aware of about cutting springs, something along the lines like "well if you have after market adjustable shocks you can cut the springs so much and would not hurt anything".

But I guess RTexasF explanation "We're outa time, do whatever" decribes the situation pretty well.

I am not going to be surprised when this car will end up in the ditch or something like that due to going 80-100mph with the front end bouncing like crazy.

[searich07]

RUS777, To lower car by cutting suspension springs is a very BAD idea; because your spring rates will be all wrong. Lowering a car is more than just short springs. Its short springs with proper spring rate, stiffer dampers to compensate for reduced suspension travel, and different alignment settings to compensate for fact that suspension is further up in its travel, Regards

Richard

[Aceman196]

If you cut the springs a little Im guessing it is ok as long as you adjust the rest of the suspension. Chip knows what he is doing i think. I would never do it to a car but I am also not a master car builder.

[searich07]

Quote Aceman196:

“a master car builder”

Does not mean that a car builder is an engineer, physicist, or mathematician or knows what spring rate even is, or how to balance spring rates, or why spring rates must be balanced.

Computing spring constant k for a compression spring that exerts a force F when deformed to length Ldef. Spring constant k is found by inverting Hooke's Law.

Rate of a spring is the change in the force it exerts, divided by change in spring deflection. It is force gradient versus deflection curve. An extension or compression spring has units of force divided by distance, for example lbf/in or N/m. Torsion springs have units of force multiplied by distance divided by angle, such as N•m/rad or ft•lbf/degree. Inverse of spring rate is compliance, that is if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. stiffness (or rate) of springs in parallel is additive, as is compliance of springs in series.

Also further computation leads to rate, deflection, and load..

Solid Height = (Number of Coils – 0.25) x Wire Diameter
Example, for a spring with 14 coils and a wire diameter of 0.5”, Solid Height calculated as:
Solid Height = (14 – 0.25) x 0.5 = 6.875

Rate= Load (lbs.) ÷ Spring Deflection (in.)
Example, if a spring deflects by 2.75” under a load of 300 lbs with Rate calculated as:
Rate = 300 ÷ 2.75= 109

Deflection = Load (lbs) ÷ Rate
Example, a spring under a load of 300 lbs with a 109 Rate with deflection calculated as:
Deflection = 300 ÷ 109 = 2.75

Load = Deflection x Rate
Example, a spring with a 109 Rate and a 2.75” deflection with load calculated as:
Deflection= 2.75 ÷ 109 = 300

Regards,

Richard

[vasekvi]

Once you do something like cut springs, it is all about show. Not about go.

[tomcarhonda]

Well cutting springs is a cheap way to go if you don't have money to go buy others. Much more of a stiffer ride because your are making the spring lose its rates. Of course you will have the desired ride height, but you will have to mess with the toe and camber.

[RUS777]

Originally Posted by searich07

Quote Aceman196:

Does not mean that a car builder is an engineer, physicist, or mathematician or knows what spring rate even is, or how to balance spring rates, or why spring rates must be balanced.

Computing spring constant k for a compression spring that exerts a force F when deformed to length Ldef. Spring constant k is found by inverting Hooke's Law.

Rate of a spring is the change in the force it exerts, divided by change in spring deflection. It is force gradient versus deflection curve. An extension or compression spring has units of force divided by distance, for example lbf/in or N/m. Torsion springs have units of force multiplied by distance divided by angle, such as N•m/rad or ft•lbf/degree. Inverse of spring rate is compliance, that is if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. stiffness (or rate) of springs in parallel is additive, as is compliance of springs in series.

Also further computation leads to rate, deflection, and load..

Solid Height = (Number of Coils – 0.25) x Wire Diameter
Example, for a spring with 14 coils and a wire diameter of 0.5”, Solid Height calculated as:
Solid Height = (14 – 0.25) x 0.5 = 6.875

Rate= Load (lbs.) ÷ Spring Deflection (in.)
Example, if a spring deflects by 2.75” under a load of 300 lbs with Rate calculated as:
Rate = 300 ÷ 2.75= 109

Deflection = Load (lbs) ÷ Rate
Example, a spring under a load of 300 lbs with a 109 Rate with deflection calculated as:
Deflection = 300 ÷ 109 = 2.75

Load = Deflection x Rate
Example, a spring with a 109 Rate and a 2.75” deflection with load calculated as:
Deflection= 2.75 ÷ 109 = 300

Regards,

Richard

Well then say for example he had calculated everything up, and then he adjusted the damper on the shocks to match.....still with he way he cut the spring it would not have the same bearing surface (nice and round all the way around) against where the top of the spring sits vs the stock spring. So then the LOAD on the spring would not be centered, it would be off to the side, which would lead to the buckling of the spring....which would equal to spring not compressing up and down, but instead it would just bent side to side......

Like I said, Chip went on and designed/engineered one off frame for this car and screwed it all up by cutting the springs at the end.

[12153]

I don't mind if anyone takes a hacksaw or torch to their springs (coil or leaf). Just don't DRIVE the car..for MY sake..as well as YOURS.

"Willy drank a Beaker, now Willy is no more. What Willy thought was H20, was H2S04."

For those who don't comprehend my poetic Chemistry analogy? Let me put it to you, in really simple English: You do STUPID stuff? Expect to get injured/killed. And possibly injure/kill innocent others. Decimal point.

[09^CBP^6MT]

If the springs are not progressive rate springs, (and depending how much was cut) it might not matter as much as people thing. Right?

[thisaznboi88]

Don't cut springs. It kills the ride makes it bouncy like a beachball. Do it right or don't do it at all.

[BigE]

I'm wondering if they just did it to test the look and ended up ordering custom spring sets before releasing the car to the owner. Foose isn't an idiot like that loser fool Dwayne, that Boyd Coddington had running his shop.

BigE