Question regarding stock 03 cobra bilsteins

[Teej281]

Hey everyone,
Im doing an IRS conversion on my GT vert and I have some quick questions regarding the stock bilsteins. Im putting coilovers on all 4 corners of the vehicle and I was wondering what spring rates these dampers can handle. I've heard some people say that the 03 cobra bilsteins are valved differently than the bilstein hd's and that they can handle a stiffer spring rate coilover spring than the hd's. Is that true? And I'm also going to try to run spring rates of 375/525. Would that be a pretty good setup? Im trying to make sure that either the front or rear is not stiffer/softer than the other. I want my car to feel very neutral in corners and that the rear isnt stiffer than the front or vice versa. If you all could help me here, I would greatly appreciate it. I used the search but didnt find anything really relevent there.

What I'm most interested in is the max spring rate coilovers that the stock dampers can accept. I contacted MM and i have not gotten any answer yet from them, but those are the CO's that Im using, in conjuntion with Bruce's bushing kit.

Any and all help is very much appreciated! :beer:

Teej

 

[LargeOrangeFont]

The OEM front struts are HDs.

325# coilover springs are about the limit for the stock Bilstein struts. With 375# springs the front the car will feel a bit underdamped when you push it hard. You will want Bilstein Sports, or send your OEM struts out to be revalved (much cheaper).

The coupe rear shocks will be ok up to 525-550# springs. The vert shocks are valved softer, and are "not recommended" for coilover use.

Also you will probably want to stiffen the back up a bit if you want it to be neutral, but it will depend on your preference and what you plan to do with the car.

 

[Teej281]

When I talked to someone at MM they told me that they could not revalve the stock struts or shocks at all? What do you mean that the car would feel underdampened? and my plans are auto-x for now and once i can have more power and be competitive i'd like to take it to track events and such just for fun. This is ultimately going to be a street car but I would like it to handle like a champ on the street as well as on the track.

 

[LargeOrangeFont]

They lied to you. Bilstein will revalve a strut for $75 and a shock for $65 plus shipping there and back. I bought used 03 Cobra struts and had them revalved to my specs instead of buying the MM "sport" valved struts. If you are going to AutoX you will want springs much stiffer than what you listed. Probably 400 or 425 up front and 600+ in the rear.

We just did custom valved Bilsteins and 425# springs on coilovers on the front a friends 95 GT and it feels great and is pretty liveable on the street.

With the OEM valving and 375# springs the car will dip and dive too much when you push the car, especially in an AutoX situation.

 

[Teej281]

I wouldnt even know where to start to spec out how i would want my shocks and struts to be valved. I'm looking to do this for fun really and not to compete competitively. But i dont want to be a slouch on the ax track either. With my current valving on the stock shocks and struts, what spring rates would you choose? I've heard 325/525 is a very good compromise.

 

[LargeOrangeFont]

You just tell Bilstein what you have and they will do it for you. Basically you tell them it is a Mustang coilover application, and you want to run 375-400 lb springs. They have a worksheet you put all the cars information on.

Or you can buy the MM Bilsten sport struts.

You will want 375 in front and 575 or 600 in the rear at a minimum for what you want to do.

325/525 will work, it will just understeer more, and have more body roll than a 375/600 setup.

 

[Teej281]

Well right now I'm kinda on a time schedule that this all has to be done in less than 3 weeks as I'm leaving in 3 weeks from today for Mustang Week. So I dont think that it is in my time frame that i need it done by. know what i mean? I can always take the car down for a month over the winter when i hardly drive it anyways and send out all the dampers for revalving and get different hypercoil springs at that point in time. Right now i'm looking for what the max i can run stock shocks and struts on. I'd love to run stiffer than what i can but time and money arent on my side right now and I'm just trying to get the thing together in time for MW.

 

[LargeOrangeFont]

Well right now I'm kinda on a time schedule that this all has to be done in less than 3 weeks as I'm leaving in 3 weeks from today for Mustang Week. So I dont think that it is in my time frame that i need it done by. know what i mean? I can always take the car down for a month over the winter when i hardly drive it anyways and send out all the dampers for revalving and get different hypercoil springs at that point in time. Right now i'm looking for what the max i can run stock shocks and struts on. I'd love to run stiffer than what i can but time and money arent on my side right now and I'm just trying to get the thing together in time for MW.

See post #2.

 

[RcodeStang]

I remember MM telling me that the cobra coupe Bilsteins can handle a 350 or 375 C/O up front. SLIGHTLY more aggressive than regular HDs I guess. MM said they can't be revalved because they refuse to revalve peoples Bilsteins to their "sport" or "race" specs.

 

[LargeOrangeFont]

I remember MM telling me that the cobra coupe Bilsteins can handle a 350 or 375 C/O up front. SLIGHTLY more aggressive than regular HDs I guess. MM said they can't be revalved because they refuse to revalve peoples Bilsteins to their "sport" or "race" specs.

Of course they did.. They want you to buy new struts from them. The Bilstein HD front strut and the OEM Cobra front strut share the same part number, they are one and the same from my understanding.

With 375# springs on OEM struts the car is ok on the street and rides fine. When you push the car you can feel it is a bit underdamped. That is probably why MM lowered their rating of the OEM front struts to 325# coilover springs.

 

[Teej281]

So what youre saying by underdampened they are going to brake dive more than they would if they had lighter springs that were better suited for the struts? Also, what is different about the Cobra R HD's than regular HD's that they are still called HD's but handle a 575lb spring?

 

[c6zhombre]

this whole issue about what bilstein valving (strut andf shock) came in the 03/04 cobras stock is a huge cluster fug. I've called many shops and dealers (like tousley) and I've gotten different answers almost every time. And then you have the side issue of what was factory spec for vert versus coupe.

I can tell you this...when i went with the h&r race springs I decided to just do brand new HD's to be safe. The car was near 6 yrs old, so why not. I couldn't be happier, it drives, brakes, and handles awesome. And this is coming from a c5z and c6z owner. And the mm steering bushings were icing on the cake, highly recommend those :coolman:

 

[Teej281]

well right now i'm just trying to get all my ducks in a row right now and before i can go any further I need to choose spring rates for my coilovers. so thats why i asked. I'm planning on maxing them out with hopefully 375/575 springs and then maybe over winter getting the shocks and struts revalved to handle 400/600lb springs.

And c6zhomebre, which steering rack bushings did you use? Urethane or aluminum?

 

[LargeOrangeFont]

So what youre saying by underdampened they are going to brake dive more than they would if they had lighter springs that were better suited for the struts? Also, what is different about the Cobra R HD's than regular HD's that they are still called HD's but handle a 575lb spring?

Bilstein HDs are a model of shock, like a KYB AGX or Tokico D spec. They make Bilstein HDs for many types of cars.

The Cobra R HD rear shocks are stiffer than regular 03/04 Cobra HD rear shocks, allowing you to use stiffer springs.

Underdamped means the springs overpower the damping of the strut somewhat. Running 375# front springs will handle better than running 325# springs on the OEM struts but the car may feel a little jittery near the limit because the springs are overworking the struts.


Always use alumnium rack bushings

 

[Teej281]

That settles it. I'm getting 375/575 springs for my co kits and then if I feel the need to revalve the shocks and struts I will later. And I'll get some aluminum rack bushings.

 

[99 KOBRA]

I run 450/575 in my '04 with Bilstein Sports

 

[Teej281]

350 550 is what I'm deciding to go with. Not too terribly out of the range but still stiffer.

 

[Teej281]

Quick update. Decided to go with the MM CO complete kit with shocks and struts and I'm going to sell the stock shocks and struts in favor of the MM Sport valved Bilsteins with 400/600 CO spring rates. Any objections?

 

[99 KOBRA]

Quick update. Decided to go with the MM CO complete kit with shocks and struts and I'm going to sell the stock shocks and struts in favor of the MM Sport valved Bilsteins with 400/600 CO spring rates. Any objections?

Sounds good