Cut Stock Springs vs. Progressive Springs
02-11-2015, 04:44 PM
#11
2nd Gear Member
Thread Starter
Join Date: Oct 2011
Location: Missouri
Posts: 227
You're worried about matching the shocks/struts to the springs...but not about cutting stock springs because you don't want to get the correct spring(s) to get the height you want?
Those two lines of thinking are totally divergent.
Most OEM springs are linear rate meaning they take the same amount of force to compress throughout their range of movement. The spring rate (in lbs/in) is designed around an expected amount of suspension travel among other things.
Most lowering springs are progressive meaning the more you compress them, the more force is needed to continue to compress them further. This allows them to be shorter (lower) because they can provide better control in a shorter distance.
When you cut a stock spring to lower a car you end up with a very bouncy suspension because you change the distance that the suspension was expected to travel. Stock springs weren't meant to work properly on lowered cars just like lowering springs would never work properly on a stock height car (if you could stretch them).
Notice I said weren't meant to work properly. I didn't say you can't do it.
Go ahead but if you're worried about matching shocks/struts to ride height, I would think properly lowering or raising a vehicle would also be of interest.
On a side note, I also see you wouldn't mind leaving the HR Brand Progressives up front and the modified OEMs out back...that could have unintended down sides like creating excessive over steer from having too stiff of a rear vs front. Springs (front/back) are matched for that reason, for balance.
Do it once, do it right but, in the end it's your car. Do what you want.
Those two lines of thinking are totally divergent.
Most OEM springs are linear rate meaning they take the same amount of force to compress throughout their range of movement. The spring rate (in lbs/in) is designed around an expected amount of suspension travel among other things.
Most lowering springs are progressive meaning the more you compress them, the more force is needed to continue to compress them further. This allows them to be shorter (lower) because they can provide better control in a shorter distance.
When you cut a stock spring to lower a car you end up with a very bouncy suspension because you change the distance that the suspension was expected to travel. Stock springs weren't meant to work properly on lowered cars just like lowering springs would never work properly on a stock height car (if you could stretch them).
Notice I said weren't meant to work properly. I didn't say you can't do it.
Go ahead but if you're worried about matching shocks/struts to ride height, I would think properly lowering or raising a vehicle would also be of interest.
On a side note, I also see you wouldn't mind leaving the HR Brand Progressives up front and the modified OEMs out back...that could have unintended down sides like creating excessive over steer from having too stiff of a rear vs front. Springs (front/back) are matched for that reason, for balance.
Do it once, do it right but, in the end it's your car. Do what you want.
Ya let me throw some $300-$400 shocks on there and turn the stiffness way up the blow them out after 10k miles. That's what I want to do.
I'm also well aware of spring rates and how they work. Yes linear spring rates require the same amount of force per unit displacement. Yes progressive springs have varying springs rates. They have an initial lower spring rate to ease the small bumps of daily driving and then a higher spring rate once you get past that. Its that initial lower spring rate that I'm worried about with how low the car is!
Besides, its not like I'm wanting to cut them for a big drop. That's what I'm trying to fix! Only temporarily mind you until I probably get some weight jacker lcas. Which opens a whole 'nother can of worms considering what springs to get later. So ya, let's go buy three sets of springs.
Wouldn't mind leaving HRs in front? That's specifically why I asked if I should swap both front and rear. That's exactly what I was thinking is that there could be loss of steering control due to the mismatch.
Sorry if I came off like a d!ck, but you kind of did too. I'm completely open to all information and I appreciate input. Nicely
Then again it is the internet and I should grow thicker skin.
Anyways, I'm all about only buying parts once. But, since these springs are causing my tires to get cut, and I need to replace my tires soon, I'd rather not cut up $1000 new tires. And until I get what I want for rear suspension permanently figured out, I need something temporarily. And a $30 set of stock cut springs seems to fit the bill best.
EDIT: I see I never mentioned this was only for temporary use, so, my bad. Let this be known going forward.
Last edited by unitedwestang; 02-11-2015 at 04:49 PM.
02-11-2015, 05:04 PM
#12
2nd Gear Member
Thread Starter
Join Date: Oct 2011
Location: Missouri
Posts: 227
If you don't mind explaining, how does cutting a stock spring create a bouncy ride?
k=Gd(wire)^4/8nd^3(coil)
Since we're not changing the material at all G, d(wire), and d(coil) all stay constant. Since the number of coils is in the denominator reducing it (cutting a coil) would decrease the denominator therefore increasing k (spring rate) making a "stiffer" spring.
I'm just going off the math, and I've been wrong before, but to me it seems as though cutting a coil from a stock spring would actually make it slightly "stiffer".
I will say that I don't think cutting stock springs for a large drop should be a permanent application, or even done necessarily. But for a small drop? Maybe. As a temporary solution? For my particular case, I don't think it will be a horrible idea. Especially since its a weekend car that I don't push in corners.
k=Gd(wire)^4/8nd^3(coil)
Since we're not changing the material at all G, d(wire), and d(coil) all stay constant. Since the number of coils is in the denominator reducing it (cutting a coil) would decrease the denominator therefore increasing k (spring rate) making a "stiffer" spring.
I'm just going off the math, and I've been wrong before, but to me it seems as though cutting a coil from a stock spring would actually make it slightly "stiffer".
I will say that I don't think cutting stock springs for a large drop should be a permanent application, or even done necessarily. But for a small drop? Maybe. As a temporary solution? For my particular case, I don't think it will be a horrible idea. Especially since its a weekend car that I don't push in corners.
Last edited by unitedwestang; 02-11-2015 at 05:11 PM.
02-12-2015, 03:13 AM
#13
4th Gear Member
Join Date: Aug 2007
Location: Stroudsburg, PA
Posts: 1,148
Cutting will make them stiffer in a bouncy way. I assume it has to do with changing the rebound rate but can't give you the technical explanation, I can say that was my experience with my '95. I found the rears much easier to predict the drop than the fronts but it's still a good idea to be cautious and cut less then you think you need to and check and cut again if needed.
You might try new urethane spring isolators as they should give you at least a little bump in height. The best option is to roll the fender lip as suggested earlier.
You might try new urethane spring isolators as they should give you at least a little bump in height. The best option is to roll the fender lip as suggested earlier.
02-12-2015, 09:23 AM
#14
2nd Gear Member
Thread Starter
Join Date: Oct 2011
Location: Missouri
Posts: 227
Thanks for the suggestions, but it already has poly isolators. Right now rolling the fenders is my last consideration. I've seen some pretty botched jobs from rolling fenders. I know you can rent the tool, I've looked into rolling fenders before. Its just my absolute last resort currently.
02-13-2015, 01:56 PM
#15
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
Glad you read my post at all.
Ya let me throw some $300-$400 shocks on there and turn the stiffness way up the blow them out after 10k miles. That's what I want to do.
I'm also well aware of spring rates and how they work. Yes linear spring rates require the same amount of force per unit displacement. Yes progressive springs have varying springs rates. They have an initial lower spring rate to ease the small bumps of daily driving and then a higher spring rate once you get past that. Its that initial lower spring rate that I'm worried about with how low the car is!
Besides, its not like I'm wanting to cut them for a big drop. That's what I'm trying to fix! Only temporarily mind you until I probably get some weight jacker lcas. Which opens a whole 'nother can of worms considering what springs to get later. So ya, let's go buy three sets of springs.
Wouldn't mind leaving HRs in front? That's specifically why I asked if I should swap both front and rear. That's exactly what I was thinking is that there could be loss of steering control due to the mismatch.
Sorry if I came off like a d!ck, but you kind of did too. I'm completely open to all information and I appreciate input. Nicely
Then again it is the internet and I should grow thicker skin.
Anyways, I'm all about only buying parts once. But, since these springs are causing my tires to get cut, and I need to replace my tires soon, I'd rather not cut up $1000 new tires. And until I get what I want for rear suspension permanently figured out, I need something temporarily. And a $30 set of stock cut springs seems to fit the bill best.
EDIT: I see I never mentioned this was only for temporary use, so, my bad. Let this be known going forward.
Ya let me throw some $300-$400 shocks on there and turn the stiffness way up the blow them out after 10k miles. That's what I want to do.
I'm also well aware of spring rates and how they work. Yes linear spring rates require the same amount of force per unit displacement. Yes progressive springs have varying springs rates. They have an initial lower spring rate to ease the small bumps of daily driving and then a higher spring rate once you get past that. Its that initial lower spring rate that I'm worried about with how low the car is!
Besides, its not like I'm wanting to cut them for a big drop. That's what I'm trying to fix! Only temporarily mind you until I probably get some weight jacker lcas. Which opens a whole 'nother can of worms considering what springs to get later. So ya, let's go buy three sets of springs.
Wouldn't mind leaving HRs in front? That's specifically why I asked if I should swap both front and rear. That's exactly what I was thinking is that there could be loss of steering control due to the mismatch.
Sorry if I came off like a d!ck, but you kind of did too. I'm completely open to all information and I appreciate input. Nicely
Then again it is the internet and I should grow thicker skin.
Anyways, I'm all about only buying parts once. But, since these springs are causing my tires to get cut, and I need to replace my tires soon, I'd rather not cut up $1000 new tires. And until I get what I want for rear suspension permanently figured out, I need something temporarily. And a $30 set of stock cut springs seems to fit the bill best.
EDIT: I see I never mentioned this was only for temporary use, so, my bad. Let this be known going forward.
ANYWAYS, having a more clear idea of what you're trying to accomplish...you can try these:
http://carphotos.cardomain.com/ride_...0013_large.jpg
They are about as easy of a fix as you can get without taking the car apart and it is meant for temporary use. They can be picked up at Pep Boys last I found or you can order them online.
I prefer those to these: http://198.173.64.150/images/superior/18-9001-demo.jpg which can fall out.
As for the bouncy ride, travel distance plays a part in the feel of the suspension. Cutting maybe one or two coils may not be as big of a deal but the shorter travel means they'll have less compression and rebound distance. Ideally the spring rate would need to be adjusted for that in order to maintain the same ride quality. Without changing it, the spring will be too stiff for the shorter travel.
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