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Premium Member
2005 CTS-V
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8,363 Posts
Discussion Starter #1
I may be replacing my FG2s soon with new FG2s. One of the fronts has failed and currently you have to buy all four.

I do not want to lower the car at all. But I would like to change the front springs to 500s and the rear springs to 550s.

Can someone tell me what springs I need to buy? More specifically what diameter (2.5" I think), what length, and any other dimension that a spring vendor will want (other than the rate which I already know), for both the front and the rear.

Thanks in advance for your help.
 

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'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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4,455 Posts
Just a thought, higher spring rates with the same length springs will probably raise the ride height of the car, no?

I have a spare set of stock springs sitting at home that I can measure or you if it would help.
 

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Premium Member
2005 CTS-V
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8,363 Posts
Discussion Starter #3
Just a thought, higher spring rates with the same length springs will probably raise the ride height of the car, no?

I have a spare set of stock springs sitting at home that I can measure or you if it would help.
I am still thinking about your first question. I don't think a minor change would bother me.

I would greatly appreciate the measurements. Thanks.
 

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'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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Ok, I took some measurements that I thought would be significant. If you want more let me know. And these are pretty close, but I don't have anything more high tech than a ruler so they may not be 100% exact.

Note: the coils stop on the top and bottom at roughly the same spot so as if you were to drop a line straight down from the end of the top coil it would hit the ground at the end of the bottom coil.

Rear:
- Coil Thickness: 1 1/8"
- Total height: 13"
- Top Outside Diameter: 3 1/4"
- Top Inside Diameter: 1 7/8"
- Bottom Outside Diameter: 4 3/4"
- Bottom Inside Diameter: 3 1/2"
Note: The bottom inside/outside diameter of the coils continues up for the majority of the spring's height (12 1/2"), then the diameter shrinks to the top diameter in the last 1/2".

Front:
- Coil Thickness: 1 1/16"
- Total height: 14 3/8"
- Top Outside Diameter: 4 7/8"
- Top Inside Diameter: 3 3/4"
- Bottom Outside Diameter: 3 1/2"
- Bottom Inside Diameter: 2 1/2"
- Note: The top (larger) inside/outside diameter of the coils continues down for 10" before the diameter starts to shrink to the bottom diameter.
(see picture of spring from the FAQ to get an idea what I am talking about)
 

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Premium Member
2005 CTS-V
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8,363 Posts
Discussion Starter #5
Ok, I took some measurements that I thought would be significant. If you want more let me know. And these are pretty close, but I don't have anything more high tech than a ruler so they may not be 100% exact.

Note: the coils stop on the top and bottom at roughly the same spot so as if you were to drop a line straight down from the end of the top coil it would hit the ground at the end of the bottom coil.

Rear:
- Coil Thickness: 1 1/8"
- Total height: 13"
- Top Outside Diameter: 3 1/4"
- Top Inside Diameter: 1 7/8"
- Bottom Outside Diameter: 4 3/4"
- Bottom Inside Diameter: 3 1/2"
Note: The bottom inside/outside diameter of the coils continues up for the majority of the spring's height (12 1/2"), then the diameter shrinks to the top diameter in the last 1/2".

Front:
- Coil Thickness: 1 1/16"
- Total height: 14 3/8"
- Top Outside Diameter: 4 7/8"
- Top Inside Diameter: 3 3/4"
- Bottom Outside Diameter: 3 1/2"
- Bottom Inside Diameter: 2 1/2"
- Note: The top (larger) inside/outside diameter of the coils continues down for 10" before the diameter starts to shrink to the bottom diameter.
(see picture of spring from the FAQ to get an idea what I am talking about)
That should be everything I need to know. Thank you.
 

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Registered
'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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4,455 Posts
No problem. :highfive:
 

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Premium Member
2005 CTS-V
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8,363 Posts
Discussion Starter #7
Can someone tell me what spring sizes, (front & rear; outside diameter & length) Ground Control includes with their coil over kits for the V?
 

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Banned
05 CTS-V
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889 Posts
i will check for you in the morning... i didnt install the fronts yet!
 

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2016 ATS Premium 6-spd MT
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14,075 Posts
If SoJersey hasn't gotten back with the info, I could probably do it. I'll have to jack my car up to get under there, and it would be several days (~4 or 5) before I'll get the chance, but I'd be willing to do that. I'll keep watching this thread.
 

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2016 ATS Premium 6-spd MT
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14,075 Posts
The cornucopia (Latin: Cornu Copiae) is a symbol of food and abundance dating back to the 5th century BC, also referred to as horn of plenty, Horn of Amalthea, and harvest cone.
 

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Banned
05 CTS-V
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889 Posts
lol good deal!!!!!
 

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'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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4,455 Posts
tbjs likes horns and cones....
 

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Registered
'06 Z06, '05 CTS-V 453rwhp/434rwtq (sold)
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4,455 Posts
Holy moly.....they use 3-4" shorter springs!! :shocked:
Interesting. I guess the stock springs compress 2"-3" more than the stiffer eibachs. I wonder what the compressed height of the stock springs is...

You think if you took the % of compression of the springs and used that to calculate how many inches to cut an uncompressed spring to achieve a certain drop/ride height that it would be fairly accurate? :hmm:

If the compressed rear springs were 10" for example, they would be compressed to ~77% of their original size. So if you wanted to drop 1" to have the compressed height of the springs be 9", you could divide 9" by 77% and get an uncompressed height of approx 11.7" which would be what you would cut the springs down to? But does the spring that was cut shorter then have a higher spring rate than it did before it was cut? :hmm:

Sounds like an experiment is in order...
 

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Banned
05 CTS-V
Joined
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889 Posts
Interesting. I guess the stock springs compress 2"-3" more than the stiffer eibachs. I wonder what the compressed height of the stock springs is...

You think if you took the % of compression of the springs and used that to calculate how many inches to cut an uncompressed spring to achieve a certain drop/ride height that it would be fairly accurate? :hmm:

If the compressed rear springs were 10" for example, they would be compressed to ~77% of their original size. So if you wanted to drop 1" to have the compressed height of the springs be 9", you could divide 9" by 77% and get an uncompressed height of approx 11.7" which would be what you would cut the springs down to? But does the spring that was cut shorter then have a higher spring rate than it did before it was cut? :hmm:

Sounds like an experiment is in order...
that sounds good to me... makes sense. i know def dont heat the springs cause then they will suck!!!!!!!!!!!!!!!!!!!!!!!!
 

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2016 ATS Premium 6-spd MT
Joined
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14,075 Posts
I didn't work out the math, but springs are usually rated in terms of lbs force required to compress them one inch. Again, I didn't work out the math, but knowing the free length and the weight of one corner of a V, you could calculate the compressed length of whatever spring you wanted. Might be some quirks, but that's it simplified.
 
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