Spring size/weight for shocks....


daytrayd

daytrayd

GT Owner
Mark II Lifetime
Apr 23, 2010
557
Austin, TX
So Ive been looking at dropping the GT for a while now, and the Eibach springs are no longer available for our car. I think the products Alex has are nice, but not exactly what I'm looking for. The ride height adjusters are cool, but I'd like a stiffer spring for the track. The adjustable shocks are cool but probably too pricey for what I'm looking to do. So my question is, what size length and spring rate are our stock springs. I found out porsche (some models) use a 70mm spring as well. They are available in different lengths and rates. So if I could find something a little shorter and stiffer I should be in business. I think they could work, I actually think the Eibach's were a relabeled porsche spring of theirs from what someone told me that called them in the UK. Anyone have any input or knowledge on this? Thanks

http://www.resuspension.com/cart/home.php?cat=371
 
You could try Stillen
 
Trying to get the correct ride height with a stiffer shorter spring with out having them custom wound would be next to impossible. Go with the T&A shocks, that way you can use standard race 10"
or 8" springs, get a proper rate and then adjust the ride heights and corner weights to an exact specification. The stock springs are way too soft and the shocks are calibrated for those springs,
T&A will calibrate their shocks for whatever springs you choose or they can help you select some that will work well.
 
Why don't you go with the KW variant. 3 suspension? I'm very satisfied with it.
 
Just get the single adjustable shocks with springs form Alex. The single adjustable (rebound and damping ) are awesome! Crank em down and you have race car performance. Soften them up for street use and your wife will even go for a ride and not complain! There is a reason he was on the Ford Gt build team and a reason why his T&A shocks are on many SCAA nation champions. Just do it right the 1st time. Its always cheaper in the long run. You will be very pleased with the product. If price is an issue, why did you buy a Ford GT?
 
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Cobrar, you might be right, but I think these springs are more universal than you think. Do you think the springs Alex uses are custom wound? I would guess not, but I cant say for sure. I know guys that installed the eibachs and the T&A 3-ways. They like the Eibachs better for street use. I hear it has to do with the metal isolators, which I know can be swapped to the stock ones, but seems to defeat the purpose of an expensive race setup in the first place. So the eibach setup is a shorter/slightly stiffer spring with the stock shock. However, they are no longer available. Hence the reason for an alternative. And from what I can tell, the eibach's were just a porsche spring, according to someone that called Eibach. For the occasional track day, I think a spring only swap it what I want/need. I dont need an expensive coilover setup that is going to lessen the daily drivability. I know some of you will disagree, but this is coming from people that have driven both setups.

And Rocketman, I agree do it right the first time is always cheaper. But I'm a little adventurous. And I didnt say price was the sole issue, and I dont appreciate being called cheap. If you fully read my post I'd think you would understand my thought process, maybe I didnt elaborate enough before.

Cavan
 
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When I called Alex he said the T&A single adjustable coil-overs are 20% stiffer at max and 15% softer than stock at lowest setting. Many have commented that at the sofest setting the ride is better than stock. I can't comment since mine are in a box waiting for the next 3 weeks until Rich and Dennis come and install them. I agree get the coil-overs which are the best of all worlds. Adjustable for ride firmness, height, and decent on the track. Can't wait to get them and my Michelin PSS tires on.

Otis
 
I'm no engineer, but I'm led to understand that simply using shorter springs will affect the performance of the shock (which is effectively already in compression because of the shorter spring). That's why Alex's spring perches are effective, they lower the car without changing the shock characteristics. At least that's what I understand it to do. For what it's worth, I had the Perches, and now I've got the Penske SA's. I really love them, no re-inventing the wheel. The variable damping is fantastic.
 
daytrayd said:
Cobrar, you might be right, but I think these springs are more universal than you think. Do you think the springs Alex uses are custom wound? I would guess not, but I cant say for sure. I know guys that installed the eibachs and the T&A 3-ways. They like the Eibachs better for street use. I hear it has to do with the metal isolators, which I know can be swapped to the stock ones, but seems to defeat the purpose of an expensive race setup in the first place. So the eibach setup is a shorter/slightly stiffer spring with the stock shock. However, they are no longer available. Hence the reason for an alternative. And from what I can tell, the eibach's were just a porsche spring, according to someone that called Eibach. For the occasional track day, I think a spring only swap it what I want/need. I dont need an expensive coilover setup that is going to lessen the daily drivability. I know some of you will disagree, but this is coming from people that have driven both setups.

And Rocketman, I agree do it right the first time is always cheaper. But I'm a little adventurous. And I didnt say price was the sole issue, and I dont appreciate being called cheap. If you fully read my post I'd think you would understand my thought process, maybe I didnt elaborate enough before.
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Cavan,
No offense mean't ! So calm down ! All is A ok….
A lot of us have been down the same road as you.The question has been asked before and I was merely giving you the BEST advice in my humble experience.I do enjoy my car as a road car and track car.Honestly this is most definitely a wonderful set up for a street/track car.If you come to the Rally you can even meet Alex and talk setup in great length.He is also a great guy. He has a vast knowledge regarding car set up.
Just my 02
Best regards,Ron aka Roketman
 
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daytrayd said:
Cobrar, you might be right, but I think these springs are more universal than you think. Do you think the springs Alex uses are custom wound? I would guess not, but I cant say for sure. I know guys that installed the eibachs and the T&A 3-ways. They like the Eibachs better for street use. I hear it has to do with the metal isolators, which I know can be swapped to the stock ones, but seems to defeat the purpose of an expensive race setup in the first place. So the eibach setup is a shorter/slightly stiffer spring with the stock shock. However, they are no longer available. Hence the reason for an alternative. And from what I can tell, the eibach's were just a porsche spring, according to someone that called Eibach. For the occasional track day, I think a spring only swap it what I want/need. I dont need an expensive coilover setup that is going to lessen the daily drivability. I know some of you will disagree, but this is coming from people that have driven both setups.
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You can do what you want to do, but to do it you will need the motion ratio of both the front and rear suspension systems, the ride heights you would like and an idea of how you want the car to handle.
If you want more precise handling you will probably want to slightly increase the stock rake angle and increase the rear spring rate ratio to front spring rate. Stock springs are 200 F. and 280 R.
You could measure the current compression of the stock springs and the ride height. Calculate a new compression distance based on where you want your ride height taking in account the motion ratio at that point you will have the desired compressed height of your "new" 70 MM springs. You will also need to know the free length of the stock springs so that you know how much load they are carrying at design position. You would then select a spring rate that might work say 300 front and 450 rear and determine what the free length of those springs would be to support your car at the correct ride height and compressed length. You might get lucky and find springs that will work from other vehicles but you might also win the super lotto. I went through this 30 years ago with my Cobra which had a bastard spring diameter, I spent several thousand dollars with Hypercoil having springs made at different rates trying to find the right handling balance. I finally went to adjustable spring peach shocks that used standard springs that I could buy for $55 each at 25-50 pound increments. You may have a high tolerance for oversteer or you may not, you will only know after you drive your set up. You could also opt for the current front to rear ratios and just scale the spring rate up but you will still need to calculate a workable length. The point of this essay is : It is easier to just buy the T&A shocks and get exactly what you want in ride and handling or even easier leave the car as is and put some Michelin Super Sports on. (265x18 F and 345x19 rear) You will get a huge gain in performance vs stock and better tire mileage too.
You might need wider wheels to accommodate these tires, but might work on stock rims I am not sure about it.
 
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I believe Alex offers 3 different spring rates for the Penskes. I have the middle one which is street/track. Stiffer than stock but great for me.

Ed
 
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