Torque Arm. Here is why.

[barbaro]

https://youtu.be/UhjQXJ6Yegs

 

[cbass]

 

[barbaro]

Thank you

 

[Mike Rousch]

This will most certainly turn into a pissing match real quick. I have a TA on my car and I personally love it, big key word here "I". No one here that knows me can dispute the car is FAST for what it is around multiple tracks. Does the TA make the car faster or slower, I honestly do not know, I just know it works for me. Again, ME. I think that there are plenty people/shops in here that know how to build a decent car with a various selection of parts. Again I think it all boils down to what the driver is comfortable with and used to.

 

[Mark Aubele]

Where is the video where it shows why you want to have a torque arm? Sat though the entire 13 minutes still don't know why you would want one over a three link.

 

[SoundGuyDave]

Because the torque arm prevents the axle from rotating around it's lateral axis. The three-link, on the other hand... Oh, wait... ;-) Also, I find it interesting to note that of all the discussion of "anti" angles, no mention was made of brake-hop, which is the catastrophic side-effect of the TA rear suspension. Just ask any F-body driver about that.

 

[barbaro]

"Catastrophic side effect?" You substitute hyperbole for argument. The catastrophic side effect that you refer to is illusory. Never experienced it. I have however, experience wheel hop from not having a torque arm. I'm sure Bruce Griggs was sitting around the shop one day and said you know what we need? "we need a torque arm on a mustang and I'm going to race it and I'm going to kick everybody's ass with that torque armed car and I'm going to hope that I can avoid that catastrophic side effect ." Between Filip and Griggs proven engineering and your hyperbole. . . I agree with them. Not even close. Btw I don't care about an F body. I don't drive an F body. An F Body has different geometry and a different suspension from what I run. So your example is absolutely irrelevant.

 

[barbaro]

Where is the video where it shows why you want to have a torque arm? Sat though the entire 13 minutes still don't know why you would want one over a three link.

Watch it again . . . Real slow. If you don't understand a word Google it. Then get back to me

 

[Norm Peterson]

"Catastrophic side effect?" You substitute hyperbole for argument.

You'd never call it hyperbole if you had seat time in certain years of the 4th gen F-body.

Keep in mind that the parts and the suspension configuration don't know what emblem the car wears and doesn't care. You should care about the F-body characteristics, because with slight differences in detail or maybe just bushing/rod end wear maybe it could be your car with the dancing stick axle in the braking zone. Not all 3-link cars hop under acceleration, either. The devil is in the details, not the badge on the car.

FWIW, I've driven F-body cars in autocross competition, and they're easy cars to drive hard as long as you stay out of brake hop.
Translation - I'm not anti-torque arm. And FWIW I've probably watched all of Filip's videos at least once.

It's easy enough to find examples of F-body brake hop in case you'd rather not take anybody's word for it. The interesting part starts about 30 seconds in. Me, I'd prefer that the fillings stayed in my teeth

http://www.bing.com/videos/search?q...27CBF27FCE8BB36C53FB27CBF27FCE8BB36&FORM=VIRE


Norm

 

[Whiskey11]

You'd never call it hyperbole if you had seat time in certain years of the 4th gen F-body.

Keep in mind that the parts and the suspension configuration don't know what emblem the car wears and doesn't care. You should care about the F-body characteristics, because with slight differences in detail or maybe just bushing/rod end wear maybe it could be your car with the dancing stick axle in the braking zone. Not all 3-link cars hop under acceleration, either. The devil is in the details, not the badge on the car.

FWIW, I've driven F-body cars in autocross competition, and they're easy cars to drive hard as long as you stay out of brake hop.
Translation - I'm not anti-torque arm. And FWIW I've probably watched all of Filip's videos at least once.

It's easy enough to find examples of F-body brake hop in case you'd rather not take anybody's word for it. The interesting part starts about 30 seconds in. Me, I'd prefer that the fillings stayed in my teeth

http://www.bing.com/videos/search?q...27CBF27FCE8BB36C53FB27CBF27FCE8BB36&FORM=VIRE


Norm

Norm, correct me if I'm wrong here, but method of mounting the front of a torque arm and the length of the torque arm can thoroughly mitigate this issue entirely no? My understanding is that the 4th Gen F-bodies had a really crappy way of mounting said torque arm to the transmission and had a super complaint bushing and a really weak design that all contributed to that.

From my own experience with the Cortex TA on my car, brake hop in autocross conditions was non-existent using street oriented pads. That car never had a set of track pads on it and I doubt ever had enough brake bite in the rear to lock up the rears or get close enough to where the TA would hop under braking. Fronts were a different story, but rears, no. Video from the underside of the car during autocross pretty much confirmed my lack of noticing it on my car.

I put a lot of faith into Filip's design and he told me that he ran the numbers himself to see just how high of %AS you could run with his T/A and how hard the rears would have to lock up to actually get the rear hopping and it was possible, but only with some brokenly stupid high %AS values and high brake torque values. Marketing? I dunno, probably, but Filip is a horrible sales person and a solid engineer!

 

[Norm Peterson]

It's like I've been saying - the devil is in the details. For the F-body, even the characteristics of the ABS came in for a share of the blame.

One you do get into a hop situation, even the geometry stops being a purely geometric thing (one of the reasons you might use a K&C rig if you really wanted to dig into this). Even the effective pivot point locations are moving around, meaning that the IC's and anti's aren't exactly holding constant either, and this is still a separate effect from the energy storage/release by anything that has much compliance.

Yes, Filip is an engineer all the way, where sales or even putting together a technical presentation does not come naturally. I'll cut him a lot of slack here, and not just because I'm pretty sure that he once worked in the same industry I spent most of my professional life in. I'll probably end up running through his videos again before this thread has run its course . . .


Norm

 

[kcbrown]

Watch it again . . . Real slow. If you don't understand a word Google it. Then get back to me

I, too, have watched the video, and understand the terms involved. He describes why a torque arm is useful (yields good anti-squat when the lower control arms are configured properly). But importantly, he doesn't explain how it is superior to the upper control arm the Mustangs come with. He doesn't even hint at how it is superior in that respect. He shows how you can get certain amounts of anti-squat with different lower control arm angles in conjunction with the torque arm. He doesn't claim that you can't do the same thing in the same way with an upper control arm setup.


Now, that doesn't mean that the torque arm he designed isn't better in at least some ways for at least some things (it could well be, and he appears to be enough of an engineer that I find it unlikely that he'd settle on that solution without good engineering reasons). It only means the video doesn't explain how it might be better, and that means the video you referred us to doesn't tell us what you claim it does (which is to say, it doesn't tell us why you'd want a torque arm instead of the upper control arm).

 

[2013DIBGT]

Can't say I've ever experienced brake hop while using the Cortex TA either. If we ignore for a minute all other cars besides a modern mustang running a properly designed TA can anyone here say they have actually experienced brake hop using a TA on a S197 Mustang? Seems to me that the only examples ever mentioned are those from an older Crapmaro or Firechicken who used a TA.

The TA and upper 3rd Link debate is always an entertaining one to watch but the fact of the matter is that there are fast cars using both approaches. I wont stand here and say the TA is the best thing since sliced bread but I do find it hard to fault when comparing it to what came on the car from the factory. I could probably list several things about the factory upper 3rd link that I didn't like at all but cant think of one thing I dislike about the TA on my car.

As usual, YMMV/IMO/IME...etc..etc

 

[Mark Aubele]

Watch it again . . . Real slow. If you don't understand a word Google it. Then get back to me

Dude seriously if you don't have any tech don't even acknowledge me as existing. You obviously have a vested interest in pushing Cortex shit. Give me a reason to run a TA over a (key words here) spherical bearing three link with proper geometry. Of course adding a torque arm, Watts and relo brackets, on top of dampers, springs and bars to a stock mustang will make the car work better. No one is debating that. Because from every video I see from those guys, that's what I see, their parts (which are quality pieces) added to a stock car. Let's see them take a sorted car such as Vorshlag's old car or Marks old car or even mine and show me how much faster it would be with a torque arm.

My Fox hopped like a motherfucker with a torque arm. Ended up putting autozone pads on the rear to basically take the braking out of it. If the S197 didn't have ABS or would too.

 

[Whiskey11]

Dude seriously if you don't have any tech don't even acknowledge me as existing. You obviously have a vested interest in pushing Cortex shit. Give me a reason to run a TA over a (key words here) spherical bearing three link with proper geometry. Of course adding a torque arm, Watts and relo brackets, on top of dampers, springs and bars to a stock mustang will make the car work better. No one is debating that. Because from every video I see from those guys, that's what I see, their parts (which are quality pieces) added to a stock car. Let's see them take a sorted car such as Vorshlag's old car or Marks old car or even mine and show me how much faster it would be with a torque arm.

My Fox hopped like a motherfucker with a torque arm. Ended up putting autozone pads on the rear to basically take the braking out of it. If the S197 didn't have ABS or would too.

The biggest advantage it has is higher %anti-squat values WITHOUT the roll steer characteristics of a 3 link and with a much more stable pinion angle relative to the driveshaft. In the case of the Cortex it's almost always in the ideal position because of where the chassis mount is. The problem with the S197's 3 link is the control arms are pretty short... with a longer control arm 3 link setup, I doubt highly the T/A setup would be viable at all... simply too much weight and not enough gain in %AS to justify using it simply because of the roll steer issue.

 

[Mark Aubele]

The biggest advantage it has is higher %anti-squat values WITHOUT the roll steer characteristics of a 3 link and with a much more stable pinion angle relative to the driveshaft. In the case of the Cortex it's almost always in the ideal position because of where the chassis mount is. The problem with the S197's 3 link is the control arms are pretty short... with a longer control arm 3 link setup, I doubt highly the T/A setup would be viable at all... simply too much weight and not enough gain in %AS to justify using it simply because of the roll steer issue.

Thank you for the tech Whiskey.

 

[DTL]

I ran a Cortex TA for about a year. I ended up taking it off and going to a heim jointed 3rd link. I still run the Cortex watts link. There wasn't anything really "wrong" with the torque arm, but I had a bit of noise from the front mount/bearing assembly, it weighed a ton and sat so low, it hung up on everything. I also had a really hard time putting power down on corner exit. It's less of an issue with the 3rd link, but I'm not sure if it's related. I changed a few things at the same time. I may put the TA back on, just to test it again, but for now, it's riding a rack in my garage.

Also, I had a 4th gen F-body, way back when. It had one of the famed Trac-link TAs on it. It hopped so bad, under braking, that it actually tore out a rod end and spit the driveshaft out.

 

[CorteXracing]

Torque Arm vs 3rd Link

There are several good observations and also some misconceptions in this thread that can probably be cleared up pretty easily.

Why is a properly designed torque arm (TA) better than the OEM 3rd link for an S197 Mustang?

The simple answer is that the TA improves chassis stability by moving the load inputs from the rear axle in both acceleration and braking closer to the center of gravity. This creates a more connected driving experience for the driver that generally leads to improvements in lap times since the driver can more easily sense what the car requires to do what the driver asks of it.

The S197 OEM 3rd link is superior to any suspension system that Ford or GM ever used on their live axle pony cars. This is especially true for the 2011-2014 models since Ford updated the geometry by lengthening the UCA. As such, all statement below will be relative to the S197 OEM suspension.

Why would we want a significant amount of antisquat in a pony car? Weight Transfer to the rear tires is why! We want to load the rear tires as quickly as possible since early power down is king when it comes to reducing lap times. Pony cars generally have significantly more front weight than rear; 52-57% front weight bias is pretty standard. When you see a car squat down a lot in the rear under throttle it is not necessarily a good thing because the entire load has not transferred completely until the car has fully squatted and takes a set. Full torque is already acting on the tires and it can easily blow them off before the vertical load arrives. What if we could transfer the load almost instantaneously instead of waiting for it to arrive? That is what antisquat (AS) does. It allows the load to bypass the spring and shocks and feed directly into the tires through the other suspension components.

Why not just go for as much antisquat as possible? Since AS locks out the springs and shocks it can cause problems. If the road surface is bumpy we want the springs and shocks as active as possible to keep the tires in contact with the road and loaded as highly as possible. Lot's of AS will not allow this to happen because it can cause the vehicle to loose traction in these conditions. This is the brake hop that people are mentioning. The specific design details of a particular platform (FOX, SN95, F-body, S197, etc) will determine how much AS can be tolerated in a given situation. The shorter wheelbase chassis (FOX, SN95, F-body) are more sensitive because a shorter wheelbase means that the total weight transfer will be higher. An S197 has a longer wheelbase and will inherently be more stable and tolerant. There are other factors at play and a couple of the most critical are the braking bias and ABS programming. Again, the S197 is far superior to the other cars with the newest S197s being the best. Not surprisingly, how the driver downshifts the car and applies the brakes needs to be a major focal point in any brake hop discussion. Drivers with sloppy footwork and poor rev-matching will have the biggest problems with a car set up with a lot of AS.

Notice that up to now we have only discussed AS without pointing any fingers at TAs or the S197 3rd link. The reason is that both the TA and the 3rd link can be set up with a wide range of AS amounts. The AS adjustment with the CorteX TA is done with the lower control arm (LCA) drop brackets on the axle. The ride height of the car also changes it a little. With the 3rd link, AS adjustment it is also done with aftermarket LCA brackets and can also be changed with an adjustable UCA mounting brackets that also allow the angle of the UCA to be adjusted. There isn’t much adjustment range in the UCA bracket because space is limited. The AS can change wildly with the 3rd link arrangement because the UCA is short and its angle changes a lot with the car lowered. This brings me to my next crucial point.

1. The CorteX torque arm, when used with adjustable axle bracket, is relatively insensitive to ride height changes. Lowering the car a lot will not cause the rear suspension geometry to go down the toilet. The S197 3rd link design was driven by packaging constraints so it has a really short UCA. When the car is lowered to track height the geometry becomes highly compromised with too much angle in the UCA leading to serious geometry instabilities. Aftermarket UCAs cannot raise the chassis pickup point high enough to fix the problem. Compromises are required.

2. Roll steer is rotation of the rear axle relative to the chassis during body roll from cornering. Roll Understeer is when the rear axle turns in the same direction as front tires going through a corner. Roll Oversteer is the when it turns opposite the front tires. We need the rear axle to roll understeer so the tires can generate some slip angle, which creates lateral grip. When we add significant AS with a 3rd link we end up with undesirable roll oversteer. If we pull out the AS then the car has trouble with off corner power down. The torque arm can be set up with more AS, better rollsteer, and a lower CG, all of which will reduce lap times. With the short OEM UCA and sensitivity of the suspension to ride height you can imagine the problems that might occur when hitting bumps with the car mid-corner. The amount of rollsteer rapidly changing with every bump causing a condition at the rear very similar to if the driver were sawing at the wheel but now on the rear axle. It’s most subtle than that but clearly this phenomenon does not help with chassis control or stability.

3. The less power, more rear weight bias, and tall ride height a car has the least benefit the from adding a torque arm. Lowered GT500 stand to benefit the most. A 2005-2010 V6 mustang will benefit the least.

4. The CorteX TA moves the pitch center of the vehicle under braking closer to the CG reducing noise dive. Combine that with increased AS you end up with a car that work amazingly well with lighter springs. Running a racecar with as soft of springs as possible is critical because it saves the tires allowing it to perform better than cars set up stiffly during a race or longer open track event. This is a double benefit for streetcars because it makes them more comfortable to drive around town. Win-Win. Anyone trying to sell you coilovers with front spring rates above 600 lb/in for S197 or S550 clearly does not understand mustang suspension setup. The car will have less mechanical grip and will go away quickly. The car might feel like it handles better at first because it will respond very quickly to steering input and might get heat in the tires faster but those perceived benefits will quickly deteriorate if performance is actually monitored.

5. For trackday guys and racers it is important to know that if conditions are smooth you can run more AS successfully. If you are on a rough and bumpy track then it is better to back off the AS and focus more on shock and spring adjustments to optimize power down.

6. The torque arm weights about 20 lb however the 3rd link and bracket that are removed during the installation are about 10 lb. So yes, a TA will add a small amount of weight however it a very small percentage considering the rear axle housing is 250 lb+ of unsprung weight. Ground clearance is not compromised because the TA is completely tucked up above the S197 exhaust system and really only reduces ground clearance directly below the differential. That means that going over speed bumps and angled driveways will not cause any problems. If you find yourself needing to straddle something in the road like a big rock or driving with one side of the car on the curb then you might have problem however those are not typical situations in a performance mustang since they were only 4x4s off the showroom floor

 

[Norm Peterson]

Filip - I get that fore/aft SVIC migration is far greater with the S197's 3-link than it would likely be with a torque arm.

But I'm also seeing that A/S% is more sensitive to ride height with a TA than the 3-link (over 10%/inch vs somewhere around 3% - 4%/inch), and in both cases it's in a direction that's going to geometrically unload the tires under braking.

I've done some geometry and plotting, and find that the shape of the A/S vs ride height plots also differ (the 3-link has a gentle "U-shape" to it, vs the TA's curve being concave down). I'm not quite sure what that means in terms of drivability - care to share a few thoughts?


I think I see what's going on with your point #4, but I'm going to think on it a bit.



I used to work for Stone & Webster - ring any bells?


Norm

 

[CorteXracing]

Filip - I get that fore/aft SVIC migration is far greater with the S197's 3-link than it would likely be with a torque arm.

Absolutely. At OEM ride height the SVIC of the 3rd link is pretty long which has inherent stability. When ride height is reduced to race height it becomes much shorter and changes significantly with bump/rebound which is the root of the problem.

But I'm also seeing that A/S% is more sensitive to ride height with a TA than the 3-link (over 10%/inch vs somewhere around 3% - 4%/inch), and in both cases it's in a direction that's going to geometrically unload the tires under braking.

True, however the with the car lowered to track height (~2 in drop) the angle of the UCA is extremely steep downhill which cause large IC fluctuations in bump/rebound. With the torque arm you can simple change the angle of the LCA using and get your IC length and AS back with the same bump/rebound stability that was there at the taller ride height.

I've done some geometry and plotting, and find that the shape of the A/S vs ride height plots also differ (the 3-link has a gentle "U-shape" to it, vs the TA's curve being concave down). I'm not quite sure what that means in terms of drivability - care to share a few thoughts?

I’ll have to think about that some more. U-Shaped up for the 3 link is probably good since as the suspension compresses the AS increases slightly giving a bit more support to the rear. The TA already has more AS to begin with so if it loose a little it’s probably not perceivable.


I think I see what's going on with your point #4, but I'm going to think on it a bit.

Yes, please let me know your thoughts. It has proven out in practice.

I used to work for Stone & Webster - ring any bells?

Yes, for sure. S&W was recently purchased by Westinghouse, a competitor to the companies I worked for (GE Power and Areva) in the nuclear industry