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Looking for feedback on the Cortex K-member and front lower control arms.

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5
7
Exp. Type
Autocross
Houston, TX
I'm upgrading the suspension of my 2007 GT500 which will spend ~70% of its time on the street and ~30% autocrossing, as well as the occasional track day. I'm going with a full Cortex strut-style suspension (coilovers, torque arm and Watts link) but am debating on whether to go with the Cortex K-member and front lower control arms or with the Maximum Motorsports K-member. Since the car will spend a good portion of its time on the street, NVH is a concern -- so I plan to go with the rubber motor mount option on the Cortex unit and use the stock Ford motor mounts for MM unit. I expect that the MM K-member would result in near stock levels of NVH, so my concern is what to expect from the Cortex unit. Assuming that the rubber motor mounts successfully address any engine-related vibration, I'd like to get some feedback on how much NVH to expect from the use of rod ends on the Cortex FLCAs. Since this same K-member and FLCAs are used in the Cortex SLA setup, any experience anyone has had with that option would be helpful too. Thanks!
 

ArizonaBOSS

Because racecar.
Moderator
8,728
2,732
Arizona, USA
I cannot comment on NVH related to the CorteX pieces as my car is a pure race car, but I can at least attest to the quality and fitment of the CorteX stuff.
 
173
298
Utah
I wasn’t sure I could answer your question, since I have the complete Cortex SLA and all the rear axle bits, and the car is stripped for TT2 (3400 with driver). It is an NVH machine, so I can’t say how much the front LCA contributes. I have to wear ear plugs the road noise is so bad. But the handling is awesome and I wouldn’t change it.

But I would recommend staying with the Cortex front K member. The adjustability of the LCA and serviceable Howe front ball joints are well worth it. So easy to adjust and change when necessary.

Plus it might give you the option of going SLA in the future. Check with Cortex on that though.
 
296
362
CA
I have the non-SLA cortex K-member. It's the race model with full spherical bearings. For a race car, it's a fantastic mod that I highly recommend, but for a street car I would spend the money elsewhere. I can't comment on the rubber bushing model.

Some cons to it:
  • W/295mm tires they rub on the control arms at full lock
  • ARH LT Headers had to be clearanced to not hit the k member.
  • The howe ball joints are great but they require much more frequent servicing per howe than a stock ball joints.
  • I was not able to get more than -2.65 of camber, even though pre-cortex k member I could get -3.5+. This is with Vorschlag CC plates and H&R struts. But for a street car, running that much camber is excessive. So not really a relative con for you.
For a street car I just really don't think you will see any of the advantages that the K-member has to offer. For a race car, you absolutely will and I 100% recommend the K-member, but for a street car I would spend the money elsewhere.

The advantages of the K-member shine and become extremely apparent when you are 10/10th's driving on a road course.

Also is this for a 3v or a 5.0? If for a 5.0, you might run into EPAS shudder problems. But can't confirm as my car is a 3v.
 
5
7
Exp. Type
Autocross
Houston, TX
I have the non-SLA cortex K-member. It's the race model with full spherical bearings. For a race car, it's a fantastic mod that I highly recommend, but for a street car I would spend the money elsewhere. I can't comment on the rubber bushing model.

Some cons to it:
  • W/295mm tires they rub on the control arms at full lock
  • ARH LT Headers had to be clearanced to not hit the k member.
  • The howe ball joints are great but they require much more frequent servicing per howe than a stock ball joints.
  • I was not able to get more than -2.65 of camber, even though pre-cortex k member I could get -3.5+. This is with Vorschlag CC plates and H&R struts. But for a street car, running that much camber is excessive. So not really a relative con for you.
For a street car I just really don't think you will see any of the advantages that the K-member has to offer. For a race car, you absolutely will and I 100% recommend the K-member, but for a street car I would spend the money elsewhere.

The advantages of the K-member shine and become extremely apparent when you are 10/10th's driving on a road course.

Also is this for a 3v or a 5.0? If for a 5.0, you might run into EPAS shudder problems. But can't confirm as my car is a 3v.
Thank you very much. This is precisely the kind of feedback I was hoping for. I think, for my purposes, the Maximum Motorsports K-member is going to be the way to go. Although it's heavier, I can run the stock motor mounts and a-arms with poly bushings. It also has provisions for adding a radiator support and transmission scoop. For an all-out race car, I'd go with Cortex all the way, but this is going to be a car that is driven primarily on the street but one that I can still enjoy when I go autocrossing and participating in the occasional track day. Again, many thanks to everyone for the feedback!
 
3
3
Exp. Type
Autocross
Exp. Level
10-20 Years
New York
I cant comment on the K member but I have had the Cortex Watts link and Torque arm on my car that sees mostly street duty on poor roads.

The Watts link is excellent with near zero nvh. I highly recommend it (only get a Lubelocker axle cover gasket rather than the foam can stuff).

The torque arm was also excellent performance wise but the NVH was extreme so I removed it. The problem was the front bushing - it produced extreme vibration under the center console area and rear axle whine so loud I was sure the axle was going - but after I removed the torque arm it vanished again. It's really a race car part IMO. Still the performance was so good I've mused of buying it again and retrofitting a stock UCA bushing on the front hoping it would give me most of the performance with little or none of the nvh. Maybe next summer...

20221123_074013.jpg
 
296
239
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
I was not able to get more than -2.65 of camber, even though pre-cortex k member I could get -3.5+. This is with Vorschlag CC plates and H&R struts.
I just ordered this for my current build and I hope this isn't true. Cortex claims:

"Adjustable lower control arm can be used to increase camber and adjust caster."

Was your effort to get camber just at the CC plates or this was a combined adjustment to the arms too?
 
Last edited:
5
7
Exp. Type
Autocross
Houston, TX
I cant comment on the K member but I have had the Cortex Watts link and Torque arm on my car that sees mostly street duty on poor roads.

The Watts link is excellent with near zero nvh. I highly recommend it (only get a Lubelocker axle cover gasket rather than the foam can stuff).

The torque arm was also excellent performance wise but the NVH was extreme so I removed it. The problem was the front bushing - it produced extreme vibration under the center console area and rear axle whine so loud I was sure the axle was going - but after I removed the torque arm it vanished again. It's really a race car part IMO. Still the performance was so good I've mused of buying it again and retrofitting a stock UCA bushing on the front hoping it would give me most of the performance with little or none of the nvh. Maybe next summer...
Thanks, FlyMyWay -- this is helpful. I've had a Griggs torque arm on my car for many years and I also experienced a noticeable rear axle whine after the install. However, I did not note the kind of vibration from under the console that you experienced. This may be due to a difference in the way the Griggs arm is attached at its forward pivot point. I've ordered the Cortex arm and will compare that front attachment point with the Griggs. If it looks like the Cortex front attachment point is going to be an issue, I may follow your suggestion and substitute a different bushing.
 
3
3
Exp. Type
Autocross
Exp. Level
10-20 Years
New York
Thanks, FlyMyWay -- this is helpful. I've had a Griggs torque arm on my car for many years and I also experienced a noticeable rear axle whine after the install. However, I did not note the kind of vibration from under the console that you experienced. This may be due to a difference in the way the Griggs arm is attached at its forward pivot point. I've ordered the Cortex arm and will compare that front attachment point with the Griggs. If it looks like the Cortex front attachment point is going to be an issue, I may follow your suggestion and substitute a different bushing.
I remember Griggs mounts their front torque arm crossmember to the chassis - welded I think - and I've also thought that such may also reduce the vibration/noise I got from under the console.

If you mod the Cortex torque arm to have a stock bushing or a thick(er) poly bushing please let me know of yr experience and results! Thanks!
 
3
3
Exp. Type
Autocross
Exp. Level
10-20 Years
New York
I have the cortex watts link, torque arm and lca’s. Definitely get more gear noise transferred into the cabin, don’t have any vibrations though
Maybe it's the better roads in fl but I got lots of noise and vibration. I kind of feel bad saying it because the performance improvement was very noticeable - the car never felt better.
 
5
7
Exp. Type
Autocross
Houston, TX
I remember Griggs mounts their front torque arm crossmember to the chassis - welded I think - and I've also thought that such may also reduce the vibration/noise I got from under the console.

If you mod the Cortex torque arm to have a stock bushing or a thick(er) poly bushing please let me know of yr experience and results! Thanks!
Will do!
 
296
362
CA
I just ordered this for my current build and I hope this isn't true. Cortex claims:

"Adjustable lower control arm can be used to increase camber and adjust caster."

Was your effort to get camber just at the CC plates or this was a combined adjustment to the arms too?
Combined.

CC plates remained in the same spot (which was maxed out).
Installed the K-member, camber was at -2.4
Maxed out the adjustability of the control arms, got to -2.65.

trying multimatic cc plates next
 

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