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What coil over spring rates?

I have a complete Koni Cup (adjustable firmness, front and rear) coil over setup, less the springs, that I'd like to install on my mostly street driven 944... What spring rates/manufacture/suppliers would you all recommend?

Thanks,
John


Last edited by John Schaefer; 10-10-2014 at 05:28 AM..
Old 10-10-2014, 05:24 AM
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Old 10-10-2014, 05:58 AM
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Do you plan to keep the rear torsion bars in place?
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Old 10-10-2014, 07:42 AM
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the spring diameter is going to be the determinant factor. the perches will need to fit the springs and visa versa. that will affect availability of rates.

whatever you do to the front, you need to account for in the rear. realize too that the rear spring rate is only 56% effective, so you have to do some math to determine what to add back there to balance out against the front.
Old 10-10-2014, 08:29 AM
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Originally Posted by flash968 View Post
the spring diameter is going to be the determinant factor. the perches will need to fit the springs and visa versa. that will affect availability of rates.

whatever you do to the front, you need to account for in the rear. realize too that the rear spring rate is only 56% effective, so you have to do some math to determine what to add back there to balance out against the front.
I've been experimenting with rates, front and rear. A friend of mine just brought it to my attention the fronts are not 100% effective... he thinks they're around 90%. So now you have to figure the spring rate number is not an absolute number but something to calculate into the equation. That being said, I'm running 550lb up front and am wanting to get my rear effective rate around 480. I currently have stock tbs and 400 lb coils... Definitely need more rear spring.
Old 10-10-2014, 06:59 PM
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yeah - with no torsions, a 480 would need an 850. subtract from 850 the rate of the torsion bar if you plan to keep it (if i knew what you had i could tell you what it was)
Old 10-10-2014, 10:00 PM
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check what i done
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Old 10-11-2014, 01:05 PM
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petros, the rear coilovers look super trick. that said, it seems that the stand-off they are attached to will be taking a LOT of force. do you they will hold up?
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Old 10-11-2014, 02:22 PM
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Thanks for the input... I would be deleting the rear torsion bars.
Old 10-11-2014, 04:04 PM
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yeah - with no torsions, a 480 would need an 850. subtract from 850 the rate of the torsion bar if you plan to keep it (if i knew what you had i could tell you what it was)
They're just stock 23.5mm bars, 126 lb rate I believe. I have a torsion bar delete carrier but decided not to run it because the rear rate I want to accomplish... The max recommended spring rate is 600 due to the rubber bushings so I need the bars in conjunction with the springs. I also am using the BMW 10.9 grade shock mount bolts. I have some 600lb springs to put on when I reindex my bars.... that should put me closer to my goal.
Old 10-11-2014, 04:19 PM
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yeah - you can't run rubber bushings on the shocks if you go torsion delete.

23.5 is indeed 126. 600 coils with the 126 torsions will put you at 462 wheel rate. that's pretty darned close to your target.

lol - that car is going to ride like it's on rocks, and i'd get a good dental plan, but the mathematical balance is pretty good.
Old 10-11-2014, 04:45 PM
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lol - that car is going to ride like it's on rocks, and i'd get a good dental plan, but the mathematical balance is pretty good.
I've also got a 20mm rear sway 25.5 solid up front, I need to go 30mm.

It's really not as bad as you think. I'm running bilstein hd strut inserts and rear shocks (that I converted into coilovers)... They do a great job on the street, with the springs considered, I couldn't be happier. Damping plays a big role in ride quality. It's also not my dd so I really don't mind at all. It sticks to the road like it's on rails
Old 10-11-2014, 05:35 PM
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i had 300# springs up front, with double adjustable hydraulic struts, which are much softer on the bumps than anything gas, and i still had to add a stacked spring to make the ride acceptable. i've done the stiff spring on these cars. sucks for street. every bump made the dash rattle. i was not looking for a rough ride though, as i am not 25 anymore.

it's all in what you want though. when i was young, i ran an mgb on the street with 750# front springs and 630# rear. THAT was a firm ride. i thought nothing of it at the time. i couldn't even consider that now though.
Old 10-12-2014, 09:25 AM
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That much in an mgb

I had a '72 gt and couldn't imagine it with those kind of rates
Old 10-12-2014, 10:36 AM
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lol - yeah - it was definitely a go cart. stripped it down to 1800#, flared it, fat tires and wheels, and spun the motor up to 165hp with an 8800 rpm redline, pushing a 7lb flywheel into a 4+3 overdrive gearbox and 4:11 gears. quick little car that outhandled anything else i have ever driven (though a couple of newer cars would not outcorner it, just not outhandle it)

what i have now in the blue 968 retains most of the stock ride quality, while firming up nicely in the corners. i've played around with a LOT of spring rates (still have a cabinet full of springs). finally i have a decent GT. the mistake i made was trying to track the car or turn it into a sportscar. it's just not well suited for that. it's a great gt though.

i continually think about doing another mgb or a tr-6, so i can have a real sportscar, and then i think about what it would be like to actually drive one, and i put that idea away. the reality is that i just wouldn't enjoy it anymore, no matter how much fun it might be to build and even drive occasionally. i just don't get the chance to have that kind of experience anymore. that's why i'm going to sell my VFR800-A. i just don't ride it. i barely get to drive the blue 968, and i'd have a very hard time getting any real kind of price for it, as it is so modified. the white one is going to go away at some point, before i modify the heck out of it and make it unsellable. i think i'm going to snatch up a new M4 convertible for a daily driver.

my point is that over the years, what i want in a car has changed a LOT. this is something to consider when contemplating modifications. what will you have when it's done, and are you willing to hang onto it for a very long time?

Old 10-12-2014, 11:03 AM
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