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fb csp/dailydriven spring rate help

Old 10-05-05, 04:09 PM
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fb csp/dailydriven spring rate help

Hey guys,

Just need some help on my rear spring setup. to tell you more about the car, it's a 82 gsl daily driven and autoxed 1 or 2 times a month. I have some power (rb header, highflow cat, 2gcdfis w/ tt) and i'm trying to sort out the suspension.

I just picked up some camber plates and coilover perch setup, from reading this board, it sounds like i'm looking for 350-400/125-175. So I think I'm going to start with 375 front and 175 rear. my question is what style spring do i need for the rear? what spring dia and what lenght is nescessary? I'm also running energy suspension bushings up front, i think stock front sway and no rear sway, and koni sport in front and koni specials in the rear. Right now i'm running es 100 tires which aren't the best, but will have to do until i get some funds

anyway, let me know about spring rate as well, i'm curious what you guys think...

Alvin
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Old 10-05-05, 06:12 PM
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Sounds like your on the right track for rates if you keep the rear suspension close to stock. It will be pretty kinda of soft up front for auto-x. My preference is the G-Force Engineering set-up which will totally fix the rear end geometry problems. If you want to do that as second step, you will end up with stiffer springs in the rear, in the 275lb range to match your 375 fronts for auto-x.

You need 5" dia springs in the rear, boxed on one end. Free height depends on what rate you end up with. About 8" with the stiffer rates (300 or so) taller for softer ones. You might need to buy a softer 10" or 12" spring and cut it to get the height you want to end up with and the rate you want. That only takes some math to figure out.
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Old 10-06-05, 09:19 AM
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I saw the camber plates and spacers you picked up in your other thread; nice stuff! But you canít use those spacers in CSP. Using them will move you to prepared or mod.
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Old 10-06-05, 07:39 PM
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i know, i just pay for the package. I think i'm going to be running stiff enough springrate that the turn in spacers won't do much anyway...

Alvin
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Old 10-06-05, 08:03 PM
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Originally Posted by jgrewe
Sounds like your on the right track for rates if you keep the rear suspension close to stock. It will be pretty kinda of soft up front for auto-x. My preference is the G-Force Engineering set-up which will totally fix the rear end geometry problems. If you want to do that as second step, you will end up with stiffer springs in the rear, in the 275lb range to match your 375 fronts for auto-x.

You need 5" dia springs in the rear, boxed on one end. Free height depends on what rate you end up with. About 8" with the stiffer rates (300 or so) taller for softer ones. You might need to buy a softer 10" or 12" spring and cut it to get the height you want to end up with and the rate you want. That only takes some math to figure out.
Good advice here! Also great advice to look up G-Force.
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Old 10-07-05, 05:01 PM
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I actually do know about gforce, but i was told that these components aren't ideal for a daily driven street car...
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Old 10-07-05, 05:20 PM
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Probably true, the rear end fixes all have sherical bearings so that could be annoying to some people. I predict there will come a time in your project when you will say, "Heck with it" and lean toward race car over street comfort. Resist that urge unless you can afford two cars. I'll bet there are a bunch of people out here that started the same way you are and ended up with a car that is fun to drive on the street for about 15 min. at a time.
In your situation I'd go for the spring rates you were thinking of and a huge front bar w/ no rear bar. Don't put urethane bushings in the rear or just put them in the lower arms. It's the upper arms that cause the trouble.
I'd still suggest you get G-Forces set-up manual. There isn't anything like it for any other car that I know of. It would take a library of books, and years of your time, to come close to getting the insight to your car the manual provides.
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Old 10-07-05, 05:51 PM
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I'm thinking of picking up the manual, I'm just going to get my springs and stuff first. I know this is back a$$ward, but there are four autoxes coming up in the next two months and i want to be at least have a decent turning car. Then I'll spend the money on the manual and do some more work...

Alvin
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Old 10-09-05, 09:48 PM
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"I think i'm going to be running stiff enough springrate that the turn in spacers won't do much anyway..."

Wrong! The G-Force turn in spacers correct the front roll center height for cars that have been lowered; they are not about spring rate, they are about fixing front geometry problems caused by lowering the ride height! Read Jim Susko's book, and save a lot of money by not making mistakes.
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Old 10-09-05, 09:59 PM
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but it doesn't matter, because as stated before, I can't run the spacers in csp, and i actually do understand that it fixes the geometry, but with stiffer spring rate, the suspension movement is reduced, so the goal is to not have it matter as much...
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Old 10-10-05, 05:21 PM
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I bought my rear springs here: http://iscracing.net/

For my car with the watts linkage 150#. 400# on the fronts. It's my primary drive to work car I would like a bit softer rear spring so I can soften the front end a bit. The Illuminas (the IT units from Mazdaspeed) can't quite control the fronts.

My car with the gForce rear end setup, 300#R and 500#F.
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Old 10-10-05, 08:34 PM
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hey guys, just one more quick question. I've ordered a set of 375 fronts, but I'm still undecided between 150 and 175 rears. I want something that is fairly neutral with a hair of over steer, would 175 be too stiff?
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Old 10-10-05, 09:33 PM
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If you don't have any urethane back there you should get what you are looking for with the 175's. That's about the limit for a stock rearend rate, much higher and the rear will try to show you the fast way around the turn all the time(by trying to pass you on the outside!)
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Old 10-11-05, 04:02 PM
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Originally Posted by speedturn
Read Jim Susko's book, and save a lot of money by not making mistakes.

I wish Jim made a book about REPU dual a-arm front and leaf sprung rear suspensions....................................... .......................
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Old 10-12-05, 07:07 AM
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BTW, I forgot to mention that my 150# rear springs from ISC, measured 175#.
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Old 10-12-05, 11:02 AM
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cool, sounds like 175 from gc/eibach!

Thanks!

alvin
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Old 05-27-07, 02:28 PM
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Alright, I'm resurrecting this post. about a year a half ago, I started getting this car built to the CSP rules. My current mods are listed below. As predicted from someone else above, I'm slowly changing over to a full race car. I've picked up a trailer and now have access to a truck.

Now, keep in mind that the driver (me) could use a lot of work, but the car with a good driver in it has given the miatas a run for their money... The current setup has been pretty good, we have ran in a lot of autoxes as well as a couple of track days. The reason I know the setup is still a bit off is because when the car is driven at the limit on street tires (driving schools and such), the car pushes initially and then goes into oversteer. Note that this does not happen on race tires (v710/A6) and the car works really well. I believe this is due to the rear suspension binding. I am picking up the g force tri link and panhard as well as the 275 lb springs as recommended. The main concern now is that I still won't be able to run the turn in spacers.

Anyway, I'm just documenting this more than anything... hopefully I'll have something favorable to report...
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Old 05-27-07, 03:31 PM
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Originally Posted by speedturn View Post
Wrong! The G-Force turn in spacers correct the front roll center height for cars that have been lowered; they are not about spring rate, they are about fixing front geometry problems caused by lowering the ride height!
Oddly enough, I found my handling to get much better the *lower* I made my ride height. Turn in (on pavement) is quick enough that it unsettles the rear, so I figure it doesn't need to be better than that.

Right now it's so low in the front that I rub the front tires on the upper chassis rail when racing. It overloads the rebound damping when that happens Despite that, I took FTD at the last outing against cars with 3x the power and twice the driven wheels.
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