I knew my engineering physics class wasn't useless after all.
Hooke's Law for spring force:
F = -kx
Where F is the force placed on the spring, k is the force constant (spring stiffness) and x is the displacement, or distance, of the stretching or compressing of the spring. The force is proportional to the force constant times the displacement of the spring when moved from its at-rest position to its fully compressed (or expanded) position.
So you run over a curb, pothole, bump in the road, small or big, or what-have-you, the chassis drops in height relative to the wheel when the wheel rises up into the fender-well from hitting the bump, and the chassis doesn't want to move because of its inertia, so the spring compresses. At a given constant speed, considering you hit the same bump over and over again at that speed, the force acting on the wheel will be the same every time. Write that down.
Subbing the necessary variables and graphing, the force acting on the spring is linear from the point of rest, which is zero net force, until it reaches its maximum displacement, or when the spring is completely compressed.
Common algebra law says that since the force acting on the spring in the said bump in the road is always the same, raising the magnitude of the displacement x must in turn lower the magnitude of the force constant k to keep F the same constant value, which is has to be in this example.
So therefore, on a spring of a given length and given stiffness, if you cut the spring you steepen the line in the graph, which means that compressing a cut spring two inches takes more force to compress than to compress a regular spring two inches, because the distance between the at-rest point and the fully compressed point of the spring is shorter on the cut spring: if you have to lower x, you have to raise k, which is the stiffness.
So if it takes more force to compress a cut spring, we must remember that the force acting on the spring from the bump is a constant. That means that on the cut spring the distance the spring actually compresses is much less, because the force on the spring moves it a shorter distance because the force constant is larger.
Here it comes: If you lower the distance the spring moves... you have to raise the force constant proportionally to keep the net force constant, which is has to be in this example. A bigger force constant means a stiffer spring, which means a BUMPY ASS RIDE ON STOCK DAMPERS. The shorter the distance the spring compresses, the bouncier the ride feels because it doesn't absorb as much of the forces from the road properly. The chassis will move much greater distances because the spring doesn't absorb momentum by moving instead. The chassis mimicks more of the road variations than the stiffer spring can.
And I think we've all gone over the fact that you need the dampening power to handle stiffer springs.
In case you got bored reading this, in layman's terms, you cut your springs, you raise the spring rate, and you get a crappy ride on stock dampers.
Okay, I'm done. Bye.
Now I could flame you becasue I have said this Oonnee Biiillliiioon(Dr. Evil voice) times or I could say good job.
Are you guys getting this? How many of you have read my posts about this? How many times did you disagree with me about what cutting does to the rate? Guess what, looks like I am not the only one who knows what I am talking about. Am i being a A-hole? Power trip you say. Sorry if it seems that way. That is not my intention. I got pretty frustrated when everyone said I was wrong(cutting/rates) and no one backed me up. Thank you UnderDog!!!GOOD JOB
BTW, when did we start talking about this again(rates/dampers)??Anyway I am glad it came up again.
*edit* Ok that was a lil harsh, but if that is what it takes to get the point across and save some members from making mistakes, so be it.
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Patrick Scott
Yeah, thats a roll cage in there.
I shall call him...Mini-Me
Last edited by PatScottAKA99XE : Aug 26th, 2002 at 10:58 PM.
I just thought I would let Mr. Hooke finally settle the spring rate argument once and for all in case it reared its ugly head again.
Thanks again - Pat
I like your ASE cert. I qualified for it because I worked at the same shop for more than the minimum amount of time and fit the requirements but since I only did mechanic work part time my boss wasn't willing to pay for the cert classes, so I just didn't do it. I eventually left that shop anyway. Such is life.
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'06 MkV Volkswagen GTI / DSG / REVO Stage I / AEM CAI / Custom 2.5" Catback
'99 Nissan Sentra GXE LE 1.6L A/T
Last edited by PatScottAKA99XE : Aug 26th, 2002 at 11:16 PM.
Damn...oh well. I DO autocross from time to time, but I decided to stop until I install my springs. A friend of mine took pics of the car at autocross, and it was scary to see that the car was about 2 inches from the ground in the corners. I was gonna get B&G springs (softer than eibach), but I wanted the stiffer ones for auto-x, so I stuck with eibach. I understand all that has been said in this thread, and I acknowlege the fact that I will be bottoming out on these bumpy-@$$ roads. As much as I hate the uneven fender gaps, I guess I'm stuck with it. I guess I'll be careful on these springs (pro-kits)...but its my mother I'm worried about....she flies over bumps without knowing. Oh well, I think I should stop reading this, because it makes me want to undo all that I have done...just kidding. Thanks for all the info guys, keep the discussion going.
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Team Serious NYC
1.6L N/A.....sold
3.0L Z Turbo.....donated
75 280Z.....new project
Mazda 6......zooom zoom ;)
any of yall knoww which ground controls are the ones listed on their website the bad sleave ones or the good ones you were talking about? They also don't have different rates listed on the website but a bunch of single digit numbers.
Originally posted by Neil any of yall knoww which ground controls are the ones listed on their website the bad sleave ones or the good ones you were talking about? They also don't have different rates listed on the website but a bunch of single digit numbers.
The good ones are the $400 ones, $400 a corner that is. They are $400 each for the rears($800 total) and $520 each for the fronts($1040 total) The fronts are $120 more because they need to get strut housings. This is what I was told when I called them. This price is for damper, threaded perch and mounts(?). You still will need to buy springs $55 each.
I think I may need to clarify what the differences are.
Ground Control coilovers - Threaded sleave kit with for use with stock or aftermarket type B14 dampers(shocks/struts). With springs(I think) One part # does all 4 corners. Total cost: about $400(with out dampers)
Advance Design coilovers - Dampers(shocks/sturts) with threaded bodies. Dual external adjust for compression and rebound. Full race capible. Shortened dampers. No springs included. One part # is only one damper. Total cost: about $2100(with springs.
Advance Design and Ground Control are basicly the same company. You get the Advance Design coilovers from Ground Control.
Originally posted by Blu200SX its nice of you guys to write a whole novel on for the pros and cons of lowering springs...yes personally i am in it for the looks cause face it. i am pretty young and this isnt gonna be my last car so "ooooooo's and ahhhhhhh's" will do just fine. im not a racer or autoxer. i have heard from people that eibach lowering springs like them and some dont. im a little poor so ill take my chances but thanks for the info anyways.
You may be in it for looks, but what you do not understand is that
they really suck. The ride is horrible, the handeling is awful, and it is dangerous. Those that like them dont relize how bad their ride is. I am not talking about racing either. For regular street use they suck.
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Patrick Scott
Yeah, thats a roll cage in there.
I shall call him...Mini-Me
Last edited by PatScottAKA99XE : Aug 27th, 2002 at 11:38 AM.
The good ones are the $400 ones, $400 a corner that is. They are $400 each for the rears($800 total) and $520 each for the fronts($1040 total) The fronts are $120 more because they need to get strut housings. This is what I was told when I called them. This price is for damper, threaded perch and mounts(?). You still will need to buy springs $55 each.
LOL so by time your done with everything (with mounts, rubbers, etc) about $2500 for suspension! Jesus christ i don't even think my 95' sentra is worth that much blue book.
To be honest, they are not good enough drivers to be able to tell that they are bottoming out. Either that or many people don't want to admit that there mods suck.
The reason I originaly worked with Ground Control to come out with a spring kit with higher rate springs is that the carwas bottoming out everywhere, even on the street. On the street a prokit car would bottom violently!
Stereotyped answer. Not all Pro-kit cars bottom out violently on the street. I drive on some of the roughest streets in Atlanta everyday on my way to work. With 3/4" cut out of my stock B14 stops, I get very little bottoming at all. And I'm good enough to know when I'm bottoming. At first, I will admit, they bottomed when my AGX's were set to 1 in the front and 2 in the rear. Now that they are on 2 in the front & 4 in the rear, the hardly ever bottom at all.
LOL so by time your done with everything (with mounts, rubbers, etc) about $2500 for suspension! Jesus christ i don't even think my 95' sentra is worth that much blue book.
There is a hefty price to pay for greatness.
Yeah, the cost of the AD set-up is in that area. Personally I think that its worth the cost to have a setup with as much adjustiblity and quality.
__________________
Patrick Scott
Yeah, thats a roll cage in there.
I shall call him...Mini-Me
LOL so by time your done with everything (with mounts, rubbers, etc) about $2500 for suspension! Jesus christ i don't even think my 95' sentra is worth that much blue book.
I'm almost ashamed to admit that the sum of all the mods on my car probably cost twice as much as my car is actually worth. And blue book never takes that stuff into account either... you'll never see that money again unless you sell the car to an enthusiast. and even then...
Stereotyped answer. Not all Pro-kit cars bottom out violently on the street. I drive on some of the roughest streets in Atlanta everyday on my way to work. With 3/4" cut out of my stock B14 stops, I get very little bottoming at all. And I'm good enough to know when I'm bottoming. At first, I will admit, they bottomed when my AGX's were set to 1 in the front and 2 in the rear. Now that they are on 2 in the front & 4 in the rear, the hardly ever bottom at all.
Just my $.02
Don't you have a stiff ride with 2 and 4 settings? People with AGX's that i've talked 2 said anything above a 3 is jaw shattering I guess in order to keep it from bottoming gotta sacrifice smoother stocklike ride for harder stiffer one. Ahhh the tradeoffs of life..
Don't you have a stiff ride with 2 and 4 settings? People with AGX's that i've talked 2 said anything above a 3 is jaw shattering I guess in order to keep it from bottoming gotta sacrifice smoother stocklike ride for harder stiffer one. Ahhh the tradeoffs of life..
2 and 5 is optimal in my opinion. However, when I had the original Place Racing motor mounts (the extremely stiff ones that have loosened every body piece on my car!) 1 and 2 was max. For some reason, when I went *STIFFER* on the AGX's, the car *FELT* looser. It was weird... lowering the suspension made the car feel stiffer. Maybe that was the car bottoming Now, with ES inserts, 2 and 5 feels best.
I agree with 96BlkSER. With softest setting (KYB AGX), my car seemed to bottom out a lot more. Right now I have setted mine 2 front 5 rear. Ride is not too stiff and with Motivational rear upper mount, it hardly ever bottom out.
My front suspension still has "major" bottoming problem because it's lowered 2".
By the way I am running B+G front (2.0" drop) and Pro-Kit rear (1.4" drop). With KYB AGX set at 2 front 5 rear. This is funny set up, but I like this set up if front didn't bottom out so much. I am just testing this for AutoX and I do not recommend anyone to try this.
well thats certainly a unique setup there. Yeah that 2.0 is a lot. Doesnt it ride strange with the softer bigger b&gs up front and stiffer shorter eibachs on the rear?
whats next you gonna put a b&g left rear, sprint right rear, sportline left front and prokit right front
Originally posted by Neil well thats certainly a unique setup there. Yeah that 2.0 is a lot. Doesnt it ride strange with the softer bigger b&gs up front and stiffer shorter eibachs on the rear?
whats next you gonna put a b&g left rear, sprint right rear, sportline left front and prokit right front
I was trying to make rear springs stiffer because my car understeered bad when I autoXed. You can reduce understeer by using stiffer rear springs, that's why I tried that set up just to see if it helps or not. There were other reasons making my car understeer so it didn't help whole lot, but it did improve the street handling.
There are two more big reason my car still understeer when I autoX. If you were following this thread, you should know the reason 1. It's suspension travel. Another one is rear toe. If I can solve those two problems, I will love the way my car rides.
You have a excellent idea about mixing 4 different springs. I might have to try that set up next.
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Oh well, I think I should stop reading this, because it makes me want to undo all that I have done...just kidding. Thanks for all the info guys, keep the discussion going.
Now, with ES inserts, 2 and 5 feels best.
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