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Help Identifying Front Coilovers & Rear Spring Question


I recently purchased a set of front coilovers from eBay (pic below). They were never installed and advertised as coming from the Shelby Extreme Grip Pkg. They came assembled with new GC Camber plates and 8", 475lb Eibach springs. I remember looking at this at the Extreme Grip Pkg on Shelby's website a while back but it is no longer available (if my memory is correct it came with coilovers, Fays 2 Watts Link, rear LCA's, etc). I called Shelby American the other day and the rep I spoke to was clueless (in general and about the coilovers or an extreme grip pkg). He told me he couldn't find anything about a suspension package that was no longer for sale on their website. He did tell me that they only used Eibach and Koni products, but never mixed parts, and since the spring are Eibach than the shocks / internals must be Eibach too. I started to ask him how they ever used / sold Koni' setups than, since they "never mix parts" and Koni doesn't mfg springs, but I stopped and thanked him then hung up.

Anyhow, to get to the original point of this anyone familiar with these coilovers? Looking at them, they appear to be exactly the same as the Cortex Xtreme grip front struts, from the GC camber plates to the offset strut housing.

Second, I'm not sure if I'm going to go with true coilovers or axel mounted springs w/ threaded perch adjuster in the rear. I will probably go with 250lb linear 2.5" springs either way, but I do not know what length to get. With 8" long springs in the front, should 8" be used in the rear too? I'm assuming 8" in the rear for a true coilovers, but I want to be sure before I purchase anything else. Is this correct?

Would I also use 8" if I go with axel mounted springs or would I want to go shorter to compensate for the length of the threaded adjuster?

Any info on these coilovers and rear spring length would be very helpful.


Shelby branded CorteX Koni coilovers? CorteX has used GC camber plates in the past.

I have Hyperco 8" 250's in the rear of my AST 4150 set-up. They are adjusted to near the top of the adjusters and have maybe 1/4" left to go up giving me around a 1-1/2" drop. I could easily go with 9" springs. My adjusters sit on a delrin insert that sits on the axle so I have some extra height built-in. You'll have to see what you're rear adjusters look like and how they are set-up on the axle before you can buy the right length springs.
I believe they are made by Cortex - not sure if they are track or street valving. The track valved Cortex setup appears to come with GC plates while the street version doesn't appear that way. However, the spring rate of 475lb seems maybe a little low for a track valved strut. I ended up emailing Cortex last night and included pictures. Hopefully they will be able to chime in and match the rear coilovers for me.

Cp85gt - thanks for the input on shock length.

Grant 302

basic and well known psychic
Post a pic of the top strut adjuster. Cortex/Koni rears are on sale now for $50 off or $1049. If you're budget is higher than that, then I'm sure you could go with the JRi SA for ~$1600.

Based on other Cortex kits/setups, I think a 250-275 rear spring should work.

If you go with the Cortex rears, then just talk to Filip about the height adjustment range that you want as there's a fair amount of room to adjust on the shocks. If you go with the Koni's, I suggest getting the tender springs and collars too.
Thanks guys. I did not get the adjustment nobs. Any idea if they can be purchased separately?

I'm hopeful that I can get the answers about the valving from Cortex then figure out what to do about rears. deciding which brand to go with is going to be a struggle for me...go the cost effective way with matcing Koni's? Lots of good things being said about the JRI. Can't go wrong with Penske's and they are only about an hour from me, which would make rebuilding convenient in the future. Only downside is the front will cost a small fortune if I want to match them down the road. I guess I will wait to see what Cortex can tell me about these fronts and then go from there.

Grant 302

basic and well known psychic
Quick search found these:
I'm sure there would be other/cheaper places to buy.

I know this might be unconventional thinking, but I wouldn't worry about 'matching' front and rear dampers. My experience is limited, but after going through the relatively steep learning curve of adjusting the CorteX/JRi DA coil overs, I definitely prefer/need more adjustability for the rear/shocks. If I were to choose again today, I think I could go with the SA front/struts and the DA rear/shocks. I don't see how I could get 350 lb/in dialed in for tolerable (to me) street driving otherwise.
Thanks for the link and the advice. I'm not against mixing and matching different front and rear brands. Of the 3 options I mentioned earlier, the Koni rears are probably last on my list even though they are the least expensives. It's my understanding that the Koni rears are not adjustable with the wheels on the car, which is a pretty big negative for me.

Also, at some point down the road I will probably look to upgrade the front again. At that ime, I will probably go with the same brand that I ended up going with for the rears this time around. So much speculation...whatever I learn from Cortex about the Koni's may completely change what I'm thinking. Decisions decisions! :eek:

Grant 302

basic and well known psychic
:) I'm not sure that I'm helping you to decide!

Let me throw one more thing in...I'd ask CorteX about costs to just replace the front strut inserts. The upgrade path may not be that expensive when you're ready for the fronts.
Lol. It's all food for thought, which is never a bad thing.

Do you mean send them these fronts when I'm ready to upgrade in the future so they can reuse the housing and upgrade to JRI, Penske or whatever internals I decide on? I don't know if I would have thought of that and the more I do, the more I think it'd be a decent cost savings. Good call, thanks! 8)
Yeah - the offset is what first made me think they could be Mfg by Cortex. When I opened the box I realized there was more to them than a run of the mill coilover, and I needed to get to the bottom of it.

I got such a good deal on them on EBay that I was initially thinking I'd just use the GC camber plates if the struts turned out to be low quality. This is turning out to be a pretty good score.


Because racecar.
Arizona, USA
Do the rears have helper springs? You might want 9" rear length at 250#. 8" would probably work too depending on your desired ride height and/or range of rear height adjuster perch.

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