cutting spring to lower car???????
K=(Gd^4)/(8nD^3)
G = material rigidity or torsional modulus
d = wire diameter
n = number of coils
D = mean coil diameter
Now when we solve for K of our cut springs, G, d, and D are constant. So we can rearrange the equation to state:d = wire diameter
n = number of coils
D = mean coil diameter
(Gd^4)/(8D^3)=k1n1=k2n2
k2=k1*(n1/n2)
So if we were to cut one coil from my 1LE springs, we can calculate the new k2N1=9 and K1=342lb/in
so k2=342(9/8) = 384.75.
The rear Z28 springs are 113 in lbs.so k2=342(9/8) = 384.75.
N1=9 and K1=113 lb/in
If we cut one coil from them:
k2= 127 inch lbs.
If we cut one coil from them:
k2= 127 inch lbs.
So the OP experienced a 2 inch drop when he cut his springs. Now he's asking the springs to absorb the same amount of load in a shorter distance with only a minimal increase in spring rate. The ride feels "pretty rough" because he's probably getting into the jounce bumpers in the front pretty often which, BTW, have an extremely high spring rate vs. the coil springs.
Note most aftermarket spring kits are in the 500-600 lb/in (front)and 150-175 lb/in (rear) range. They have to be or else the car gets into the jounce bumpers way too often.
Argument settled. Thank you, now please move on and go buy a decent set of springs.
I was being sarcastic. I'm used to responses like "You shouldn't cut springs just because I think it's bad". Obviously all that math is going to confuse some people on here. I appreciate the facts though.
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Thread Starter
Registered User
Joined: Jul 2009
Posts: 7
Likes: 0
holy **** guys i didn t think i would have this many people on this wow..Thanks alot for the coments....My car looks pretty good But { rides like a tank } at first it was ok now its just annoying im going with some good lowering springs..I just thought i could save a few bucks but its not worth all the bumpping around...LoL i need a smoother ride and will never in my life time do this **** again..Was truely a waste of time on my part.. So anyone thinking of doing it. DONT DO IT IF YOU PLAN ON DRIVEING THE CAR PAY THE MONEY FOR SPRINGS AND SHOCKS....
Jimmy you are right. By removing coils the spring rate does increase, but not by that much. The equation for calculating spring rate is:
(Gd^4)/(8D^3)=k1n1=k2n2therefore we can solve for k2
So the OP experienced a 2 inch drop when he cut his springs. Now he's asking the springs to absorb the same amount of load in a shorter distance with only a minimal increase in spring rate. The ride feels "pretty rough" because he's probably getting into the jounce bumpers in the front pretty often which, BTW, have an extremely high spring rate vs. the coil springs.
Note most aftermarket spring kits are in the 500-600 lb/in (front)and 150-175 lb/in (rear) range. They have to be or else the car gets into the jounce bumpers way too often.
Argument settled. Thank you, now please move on and go buy a decent set of springs.
K=(Gd^4)/(8nD^3)
G = material rigidity or torsional modulus
d = wire diameter
n = number of coils
D = mean coil diameter
Now when we solve for K of our cut springs, G, d, and D are constant. So we can rearrange the equation to state:d = wire diameter
n = number of coils
D = mean coil diameter
(Gd^4)/(8D^3)=k1n1=k2n2
k2=k1*(n1/n2)
So if we were to cut one coil from my 1LE springs, we can calculate the new k2N1=9 and K1=342lb/in
so k2=342(9/8) = 384.75.
The rear Z28 springs are 113 in lbs.so k2=342(9/8) = 384.75.
N1=9 and K1=113 lb/in
If we cut one coil from them:
k2= 127 inch lbs.
If we cut one coil from them:
k2= 127 inch lbs.
So the OP experienced a 2 inch drop when he cut his springs. Now he's asking the springs to absorb the same amount of load in a shorter distance with only a minimal increase in spring rate. The ride feels "pretty rough" because he's probably getting into the jounce bumpers in the front pretty often which, BTW, have an extremely high spring rate vs. the coil springs.
Note most aftermarket spring kits are in the 500-600 lb/in (front)and 150-175 lb/in (rear) range. They have to be or else the car gets into the jounce bumpers way too often.
Argument settled. Thank you, now please move on and go buy a decent set of springs.
What springs do you recommend? http://www.stranoparts.com/partdetai...D=18&ModelID=7 ?
TECH Resident
Joined: Jun 2008
Posts: 755
Likes: 1
From: Gainesville, FL
Yup - you're right. I finally found a place that 'splained it to me!
Now, got another question. Pasted below is a pic of a stock rear spring (on the left). If you cut the bottom coil, it won't seat on the axle properly. If you cut the top, it won't seat in the upper pocket properly. So, either way, you've got a spring that's not seating properly. How do you get away with this? The front's are the same, with a smaller diameter bottom and the top where the last coil is not coiled at the same angle as the ones below. How do you get the car handling properly?
Now, got another question. Pasted below is a pic of a stock rear spring (on the left). If you cut the bottom coil, it won't seat on the axle properly. If you cut the top, it won't seat in the upper pocket properly. So, either way, you've got a spring that's not seating properly. How do you get away with this? The front's are the same, with a smaller diameter bottom and the top where the last coil is not coiled at the same angle as the ones below. How do you get the car handling properly?
A friend had that problem on a car. he had to use a torch to heat it up and bend the top in a little so it would sit properly. I'm guessing he put vice grips on the spring and just pushed it inward while hot. Did it and they ended up sitting perfectly. car lowered like 2" even all around. this was like in 2007 and it still sits perfect.
zombie thread... but i cut mine a few weeks ago and did the heather hose mod at the same time... well that was too low for my 305s sticking out and i hit a decent sized dip in the road and it took a slice out of my brand new tire from the fender... i repaced the isolater and now its fine... if the tires didnt stick out from the wheel well a little it wouldnt be a problem
oh and i took out one full coil... used a dremal and a cut off wheel (or two....or three... or fifteen, lol) and it was fine... with the coil cut and the isolater out it dropped about an inch and a half but my trans am was a 4x4 anyway
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
Ive seen a coil cut on the front and the owner said it rode fine. Car was lightened some in the front (150 lbs) though so that may have effected it.
12 Second Club
Joined: Feb 2006
Posts: 876
Likes: 0
From: Catlettsburg, Ky
Meh... I cut 3/4 of a coil off my rear springs and removed the isolators as well. Still running stock shocks, and consistently pull 1.52-1.54 60' every time at the track, front tire hanging 6" in the air.
I seriously doubt putting a "drop" spring on my car is going to improve the performance much more than it already is.
I seriously doubt putting a "drop" spring on my car is going to improve the performance much more than it already is.
I had lowering springs in the rear and thought they sat a little too low, so just a couple weeks ago I cut my stockers, figuring if I didn’t like them I’d just swap back on the others. I couldn’t be more happy with either the ride or the stance. They ride just as good as they did uncut, and look great. I didn’t like the way my car leaned excessively to the passenger’s side, so I cut 1 coil off passenger and 1.5 off driver.
TECH Senior Member
Joined: Jan 2004
Posts: 5,798
Likes: 16
From: St.Charles MO
Meh... I cut 3/4 of a coil off my rear springs and removed the isolators as well. Still running stock shocks, and consistently pull 1.52-1.54 60' every time at the track, front tire hanging 6" in the air.
I seriously doubt putting a "drop" spring on my car is going to improve the performance much more than it already is.
I seriously doubt putting a "drop" spring on my car is going to improve the performance much more than it already is.