Cortex Torque Arm Racechrono Track Review

[dontlifttoshift]

You should pay attention to the FRONT UCA bushing then, because that is where all the deflection is occurring in the whole setup. It's disgusting to say the least.

I watched it again, there is a lot of deflection in the front bushing. It looks like a lot more than in the rear.

Drag racing is pretty violent.

 

[dontlifttoshift]

If a forces are high enough at instant center to push up on the car aren't those same forces pushing down on the tire resulting in increased traction?

I always thought when the car squatted on acceleration, THEN it was unloading the springs.

Nope. While the car is in the process of squatting, the springs are compressing, which means that they have to be gaining load. However, this also means that the springs aren't carrying as much load as they will when the car finally gets to its equilibrium squatted position. Going back to the previous post about the geometric anti-squat effect happening the soonest in an acceleration squat event, you have to think dynamically. IOW think of these things in terms of how they vary with time, and think in very short time steps.

So my second statement is untrue? Makes sense.

The first part is right, isn't it though. If a torque arm (or any suspension) is arranged in a way so that when it accelerates from a standing start it lifts the rear of the car, geometrically the force pushing up on the car would HAVE to push down on the tire resulting in more traction despite a slight unloading of the spring. Obviously, the AS% numbers would be way out of range for this particular subforum but is my thought process completely flawed. I shouldn't even call it my thought process, this is the way I interpret Herb Adams explanation of how AS works.

 

[Norm Peterson]

The first part is right, isn't it though.

Yup.


Norm

 

[Wes06]

christ thats alot of deflection on stock uca, im ready to put my aftermarket one in now

 

[neema]

DTL - I would hope that since PA control is pretty good with a TA that the TA would be fabbed to provide very close to an optimum PA setting. Just enough U-joint angle to keep all the little needle rollers in the joint rolling. Perhaps shimming the chassis side pickup down might be possible for very small adjustments in the negative direction if they were truly needed.


Norm

So I'm guessing the TA mounts where the driveshaft pivots up front, keeping PA the same? If so, awesome. That means PA can be kept near 0° almost all the time?

 

[Whiskey11]

So I'm guessing the TA mounts where the driveshaft pivots up front, keeping PA the same? If so, awesome. That means PA can be kept near 0° almost all the time?

Depends on the TA. The Cortex Racing unit mounts to the central bearing support brace for the driveshaft (so basically at the middle bearing on the driveshaft). The Griggs unit is longer and requires exhaust modification. And yes, near 0º all the time since there shouldn't be any deflection of the TA.

 

[DTL]

^ this.

Only thing I would add is that the front mount attaches to the driveshaft center support bearing mount AND 4 factory studs in the floorpan/subframe area. It's a pretty stout bracket.

 

[sheizasosay]

http://www.s197forum.com/forum/showthread.php?p=1634429#post1634429

Post 4 with the video. You can see Barbaro is definitely over 100% AS in the video. I wonder if that was with the TA or UCA during that video.

 

[neema]

http://www.s197forum.com/forum/showthread.php?p=1634429#post1634429

Post 4 with the video. You can see Barbaro is definitely over 100% AS in the video. I wonder if that was with the TA or UCA during that video.

what are you looking at that indicates 100%+ AS (anti squat right? not axle steer)? i think this video was pre-TA

 

[Whiskey11]

what are you looking at that indicates 100%+ AS (anti squat right? not axle steer)? i think this video was pre-TA

I think he is looking at the rear wheel well. I'm not 100% sure how suspension geometry comes into play on a dyno. A part of me wants to say that weight transfer doesn't happen in the same way on a dyno as it does on a road, but I could be wrong.

 

[sheizasosay]

Yeah rear tire well.

I have seen both squat and anti squat on S197's on a dyno. Whether I'm right or wrong I don't know for sure, but I place my money on weight transfer happens on the dyno.

The force is gonna go through the drive train. It's gonna go through the links and the geometry of those links should still come into play ....in my mind anyway.

 

[sheizasosay]

Goddamnit...I just rode my car up on some boards so I could get the jack under there and put the rear on stands so I could put the gopro on the UCA. Of course the lighting looks a lot different with the rear of the car 2 feet in the air. I wouldn't have guessed it would be that dark. My under-car video of my watts wasn't like that at all. Maybe because it was 8pm when I did it, but it was bright. Oh well...maybe I'll get motivated and tape a light under there. What a waste. Sorry

 

[Norm Peterson]

Yeah rear tire well.

I have seen both squat and anti squat on S197's on a dyno. Whether I'm right or wrong I don't know for sure, but I place my money on weight transfer happens on the dyno.

The force is gonna go through the drive train. It's gonna go through the links and the geometry of those links should still come into play ....in my mind anyway.

Pretty sure it depends on how the car is tied down.

If the car could be restrained by a cable tied to the chassis up around CG height, you'd have a much better representation of where the aero drag force and inertial forces act. You'd have a greater chance of wheelstanding depending on precisely how the rear tires were grabbing the roller.

Tied off at the axle, you've essentially added one or two more suspension elements, so neither the car's own link forces nor the squat/lift would be the same. That doesn't necessarily mean zero squat either, just that anything observed would not be representative of what happens when the car isn't tied down.


Norm

 

[Sky Render]

Wouldn't >100% rear AS be beneficial on a front-wheel-drive platform, as acceleration would push the rear end up, putting more weight on the front axle?

 

[Norm Peterson]

Nope.

1. There is no "anti" effect on an axle that is not developing longitudinal grip at its contact patches. Suspension motion there is due only to load transfer and can happen only as fast as that suspension can gain or lose load and only in the direction associated with the change in spring load. Spring and shock effects only.

2. you absolutely do not want the tail to rise with FWD, as that would raise the sprung CG even further and increase load transfer off the drive wheels. It's important to realize that the "wheelie bars" on FWD drag cars aren't there to limit rear squat (and certainly aren't there to prevent wheelstanding) - what they really accomplish is lengthening the effective wheelbase to reduce rearward load transfer during acceleration.

(Edit to the above - some years ago it was amazing how many FWD drag guys put those bars on with no idea at all why . . . other than somebody else who was fast somehow made it work. Monkey see, monkey do at its finest.)


Norm

 

[Whiskey11]

I figured I should update this. I called Cortex today and talked to Filip who answered after hours (seriously, thanks Filip) a few of my questions. Here are the questions asked followed by the answers:

1.) Does the Cortex torque arm work with the stock stamped steel diff cover?
The Cortex unit is designed to work with a specific differential cover and it has to be either the FRPP Low Profile one they sell on their site or the Cortex Watts link diff cover. However, he said that they just got a Ford Racing complete rear end in with the stamped steel cover and he would check if it could be made to work. He was less worried about the diff cover mounting points than he was about the mounting points on the cast portion of the diff housing. He was going to snap a few pictures and make sure it would be doable. He was also quite aware of the SCCA clarification that doesnt allow aftermarket diff covers in ST and SP.

2.) Does it work with the stock lower control arms?
Yes it does. He said initially there was concern about shorter springs coming out of the pockets but he mentioned that there are half a dozen or so people racing their GTs with the stock LCAs without issue. He did say that there might be a slight increase in fore/aft movement but not enough to cause problems.

3.) Does it work with the stock driveshafts?
Yes, yes it does and it bolts in using OEM hardware with plenty of clearance for either aftermarket one piece units or the stocker.

That said, Im stupid impressed. I was expecting voicemail and got the man himself and he was happy to answer questions even though he was technically closed and about to unload a race car. He has won my business.

 

[55R2014]

That said, Im stupid impressed. I was expecting voicemail and got the man himself and he was happy to answer questions even though he was technically closed and about to unload a race car. He has won my business.

I have been impressed with Filip and the Cortex crew. I was up there last week and he took time out of his busy day to talk with me. I made an appointment with him for next week to have him change out my suspension. I'm very excited to say the least.

 

[sheizasosay]

He's accessible and a smart guy and I dig what he has to offer....but you should have asked him what does a TA have have on a 3-link that is adjustable.

 

[Whiskey11]

He's accessible and a smart guy and I dig what he has to offer....but you should have asked him what does a TA have have on a 3-link that is adjustable.

If I get the opportunity to ask him again, I will. He's stupid busy right now and I don't really want to burden him any more than I already have.

I'm not a TA has any advantage on a 3 link setup with full adjustability and no requirements for bushings, but in my case, I think a TA is going to be a better arrangement for an S197 that is severely limited in modifications to the rear geometry. About the only thing I can do is swap bushings to something non-metallic and replace the UCA. The only adjustability is the length of the UCA. That means I'm stuck with basically OEM geometry but down a bunch on ride height. At least with this setup I should get a lot better bite out of the rear end of the car which will be necessary to put the 265's to good use. If it makes the car easier to drive at the limit, then that is a HUGE bonus too!

 

[sheizasosay]

The only adjustability is the length of the UCA.

The UCA mount can change the AntiSquat drastically. Should have clarified.