BMR Extreme (or whatever they are calling it) UCA or Cortex TA

[Brandon302]

As the title states, which would you go with? Though the Cortex TA is close to twice the price money isn't exactly an object. I know a good TA is supposed to help plant the rear but have also heard of axle tramp under hard braking. Which would you go with?

 

[Brandon302]

Is the UCA in question.

 

[pufferfish]

I looked at this for a while when I first got I to my 11 after my MM TA equipped 95 track rat. I ended up going with an adjustable UCA for the time being, as they are cheap and easy to install. I have yet to determine a need for anything more other than the fact that the UCA transmits way too much gear noise into the cabin.

The UCA killed all my wheel hop under acelleration and never have issues in corners. Now , if I do decide to go forced induction someday, I may have to revisit the idea

 

[steveespo]

I agree with Steve, for a track car get a spherical bearing UCA, I got the Steeda and it works very well, Multimatic piece would be awesome but I saved the $$$. There is a video on you tube that shows what happens to the UCA bushings under acceleration and it is amazing, stock bushing literally stretches back the full depth of the sleeves on the diff housing and UCA, wheel hopping like crazy.
Guy installed a BMR and the movement was stopped and wheel hop was gone. Traction arms work but again I wouldn't want to add weight when the problem can be solved with out doing so.
Steve

 

[Brandon302]

Thanks for the insight, this isn't going to be for my car, it will be for the next track rat that will hopefully stay on the track this time. I wanted to find something that was extremely stout but also want the best possible handling for the rear, which is why I was wondering if a TA or UCA would be best for a pretty much strictly track car.

 

[Cherno134]

I have the Cortex Torque Arm and decided to go that route because: 1) I didn't want the noise in the car from a spherical bearing Upper Control Arm and 2) I had previous experience with a Maximum Motorsports torque arm on a 1998 SVT Cobra Mustang.





On the Cobra I liked the way it made the rear end of the car much more predictable than the OEM 4-link suspension and gave it more grip under acceleration and deceleration and bumpy corners did not upset the car's balance and reduce grip. Based on that experience I was comfortable going with the Cortex Torque Arm.

I never experienced axle tramp in the Cobra in over 10 years of tracking it on 12+ different tracks. I'm running H&R race springs with the front 750-850 lb-in and the rear 350-390 lb-in. The shocks are Tokico Illuminas (5-way adjustable).

In the 1 1/2 years I had the Cortex torque arm on the Boss I have experienced axle tramp only at one track. High Plains Raceway, East of Denver, CO. It has happened 3 or 4 times approaching turn 8 when I got on the brakes hard while running the full track, clockwise. I am currently running the stock Tokico LS shocks and have the Steeda Boss springs - Front 225 lb-in, Rear 195 lb-in. Over the winter I am installing the Cortex JRI DA struts/shocks with 550 lb-in front springs and 325 lb-in rear springs. I am anticipating with the higher rate rear springs and the JRI DA shocks I will be able to dial out the axle tramp I have seen at turn 8.


HIGH PLAINS RACEWAY

 

[Brandon302]

I have the Cortex Torque Arm and decided to go that route because: 1) I didn't want the noise in the car from a spherical bearing Upper Control Arm and 2) I had previous experience with a Maximum Motorsports torque arm on a 1998 SVT Cobra Mustang.





On the Cobra I liked the way it made the rear end of the car much more predictable than the OEM 4-link suspension and gave it more grip under acceleration and deceleration and bumpy corners did not upset the car's balance and reduce grip. Based on that experience I was comfortable going with the Cortex Torque Arm.

I never experienced axle tramp in the Cobra in over 10 years of tracking it on 12+ different tracks. I'm running H&R race springs with the front 750-850 lb-in and the rear 350-390 lb-in. The shocks are Tokico Illuminas (5-way adjustable).

In the 1 1/2 years I had the Cortex torque arm on the Boss I have experienced axle tramp only at one track. High Plains Raceway, East of Denver, CO. It has happened 3 or 4 times approaching turn 8 when I got on the brakes hard while running the full track, clockwise. I am currently running the stock Tokico LS shocks and have the Steeda Boss springs - Front 225 lb-in, Rear 195 lb-in. Over the winter I am installing the Cortex JRI DA struts/shocks with 550 lb-in front springs and 325 lb-in rear springs. I am anticipating with the higher rate rear springs and the JRI DA shocks I will be able to dial out the axle tramp I have seen at turn 8.


HIGH PLAINS RACRACEWAY

Awesome info, thank you. Does axle tramp occur because the springs in the rear are too soft or the shocks are too soft to adjust quickly enough?

 

[Cherno134]

Awesome info, thank you. Does axle tramp occur because the springs in the rear are too soft or the shocks are too soft to adjust quickly enough?

Short Answer: Yes, Maybe

Long Answer: I talked at length about this with Filip Trojanek @ Cortex. It could be the rear springs are too soft, or the shocks are not responding quick enough, or the rear brake pad is too aggressive, or I'm just getting on the brakes too hard, or I need more rebound damping or there are surface undulations in the approach to turn 8 that are compounding soft spring or shock rate effects. I was puzzled why I saw axle tramp going into turn 8 but not at turn 13 where approach speed and braking is similar. So I have a lot of dials to turn to see if I can dial this out. Like I mentioned in my post above, this particular turn on at HPR is the only time I have experienced axle tramp in either of two Mustangs with a torque arm in 12 years at 12 different tracks. If I can't dial it out, I will just change my braking strategy for this corner - I like the other positive aspects of the torque too much to even consider changing it to competition rear upper control arm.

 

[JScheier]

this particular turn on at HPR is the only time I have experienced axle tramp in either of two Mustangs with a torque arm in 12 years at 12 different tracks.

Are you local to HPR? I can't recall seeing a black LS out there before.... but I'm usually only out there with NASA or BMWCCA.

 

[Cherno134]

Are you local to HPR? I can't recall seeing a black LS out there before.... but I'm usually only out there with NASA or BMWCCA.

I'm in Littleton. I have been going out to HPR on Friday open track days.

I talked with you some at the Hastings Roundup this year.

 

[JScheier]

I'm in Littleton. I have been going out to HPR on Friday open track days.

I talked with you some at the Hastings Roundup this year.

ahhhh..... now I remember. It's hell getting old

 

[Brandon302]

Short Answer: Yes, Maybe

Long Answer: I talked at length about this with Filip Trojanek @ Cortex. It could be the rear springs are too soft, or the shocks are not responding quick enough, or the rear brake pad is too aggressive, or I'm just getting on the brakes too hard, or I need more rebound damping or there are surface undulations in the approach to turn 8 that are compounding soft spring or shock rate effects. I was puzzled why I saw axle tramp going into turn 8 but not at turn 13 where approach speed and braking is similar. So I have a lot of dials to turn to see if I can dial this out. Like I mentioned in my post above, this particular turn on at HPR is the only time I have experienced axle tramp in either of two Mustangs with a torque arm in 12 years at 12 different tracks. If I can't dial it out, I will just change my braking strategy for this corner - I like the other positive aspects of the torque too much to even consider changing it to competition rear upper control arm.

Pretty much sold me on the TA, how do you adjust the pinion angle though?

 

[Cherno134]

Pinion angle is mostly "fixed" with the torque arm.

The torque arm is bolted to the the rear axle in three locations.
1) At the rear there is a horizontal bolt to attach the rear of the torque arm to the bracket bolted to the differential cover.
2)Forward of the differential housing there are two vertical bolts that bolt to the two triangle shaped wings that are part of the cast iron differential housing. After aligning the torque arm and other brackets, two 1/2 diameter holes are drilled into the differential housing "wings" for the vertical bolts to pass through.

After the three bolts are installed and tightened the torque arm is fixed to the rear axle. No more axle windup. The axle is "fixed" with respect to rotation after the torque arm is installed. Pinion angle will only change slightly as the rear suspension moves through it motions under compression and extension.

The front of the torque arm is supported by a new bracket that is installed under the OEM driveshaft center support location. The bracket uses existing bolt holes and studs to fasten it to the car floor pan. The pipe "nose" of the torque arm is inserted into a elastomer lined "socket" on the new bracket. The "socket" has a grease fitting to grease the connection. The nose and socket connection allows the torque arm to move fore and aft as the rear axle moves up and down.

 

[steveespo]

Cortex specifies that adjustable lower control arms are required. Is the rear axle moved forward or back with the TA? Or do you adjust pinion angle with them? Would love to see the install instructions and diagrams to understand what is happening there.

 

[Cherno134]

Steve, I had the same question...see the email exchange below:

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On Mon, Jun 9, 2014 at 9:29 PM
Subject: Torque Arm Installation Question

Filip,

I noticed the following note on the Cortex Racing product web page for the Xtreme-Grip Torque Arm: “ ***Requires adjustable length lower control arms*** "

The Torque Arm installation instructions I received last September do not mention that adjustable length lower control arms are required and/or how to adjust them.

QUESTION: Have the installation instructions been updated to include adjustable lower control arms?

I have Maximum Motorsports Extreme Duty Lower Control Arms (Mm5rlca-53). These are adjustable length lower control arms. Maximum Motorsports preset the control arms to Ford stock length. I also have the Ford Racing lower control arm relocation brackets (M-5650-A).

I have driven the car several times on track since installing the torque arm last fall and everything seems ok. With the torque arm I can put down the power earlier on a corner exit with confidence and predictability. However, the note about adjustable lower control arms being required on the product web page has me wondering if I have additional adjustments to be make on my torque arm installation.

Thanks,

Al

/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*

Sent: Wednesday, June 18, 2014 11:06 AM
Subject: Re: Torque Arm Installation Question

Hi Al,
The adjustable lower arms are recommended but may not be necessary. Some aftermarket rear coil spring packages need arms that can be shortened since installing the torque arm usually moves the rearend housing rearward about 1/4-1/2". If the spring have a large diameter it may cause them to bow enough to cause some rubbing inside the frame rail cavity. None of this is a concern on a coil over equipped car. If yours is working then you are fine.

Thanks,

Filip Trojanek
CorteX Precision Technology
415.489.0866

 

[Cherno134]

 

[Grant 302]

The brake hop is likely induced when the instant center is raised dynamically, and the only members to locate the axle vertically are the shocks and springs. Too much rebound and/or surface bump then the rear tires will be effectively lifted or unloaded enough to lose traction...and that causes the hop. With the torque arm, it may be as simple as the brake dive contributing to pitch the arm down and directly lifting the axle. How tight is that front bushing/sleeve?

 

[steveespo]

The brake hop is likely induced when the instant center is raised dynamically, and the only members to locate the axle vertically are the shocks and springs. Too much rebound and/or surface bump then the rear tires will be effectively lifted or unloaded enough to lose traction...and that causes the hop. With the torque arm, it may be as simple as the brake dive contributing to pitch the arm down and directly lifting the axle. How tight is that front bushing/sleeve?

Good analysis Grant, the same reason it helps plant the rear under acceleration, is causing it to "lift" the rear under deceleration. Might get messy if you are trail braking into a corner.
Personally, I think I'm good, saving the weight and $1800 and will stay away from both the torque arm and the Watts link. I now have a 302R type suspension on the car and don't have any acceleration issues and the car performs on the brakes like a champ.

Al seems to like his setup so there is a good source of knowledge supporting the Watts/TA setup, can't wait to hear all the impressions from the Cortex buyers this spring.
Steve

 

[Cherno134]

Grant -
The bushing sleeve connection is not tight. The clearance between the OD of the torque arm "nose" and the ID of the elastomer lined sleeve is about 1/16". I haven't crunched any numbers, but could see where the IC would be raised under hard braking - with the brake dive of the car front and lifting of the rear. I changed the stock springs a couple of years ago to the Steeda Boss springs and brake dive was significantly reduced. It could be that the few times I experienced rear axle tramp when I was hard on the brakes will be solved with higher rate front springs.

Steve -
Trail braking to get the car to rotate has not been an issue.....the brake pedal pressure to trail brake is very low compared to dive bombing into a tight radius corner. Under braking the vertical reaction at the front of the torque arm is down and is applied near the center of the car, and would be generally evenly distributed fore and aft. But then again, I haven't done the math either.