Torque Arm. Here is why.

[barbaro]

Right. But now that we've seen that, we can all make points well! Win-win in the end.


Interesting. I have to wonder what that does to the balance. With the adjustable Watts Link, however, you can control the rear roll center of the vehicle, and maybe that's enough to get the car back into balance, at least with respect to neutral throttle.


Yeah, that's exactly the experience I've had as well (see, subjective impression is valuable!).

Even just going from the 24mm rear bar that came stock with the car to the 26mm Laguna Seca rear bar has made a major difference in terms of the turn-in responsiveness of the car. It went from the turn-in delay (which is really the amount of time it took the car to take a set -- the actual direction change delay of the car seemed to be much shorter than the time it took the car to take a set, which was odd) of maybe a couple of hundred milliseconds to something low enough that I can't detect it.


Oh. You no longer have that in the rear anymore? Given what you say below, I guess that makes sense.

Yes, I agree, the car is easy to drift now. But that makes it a lot of fun, even if it isn't as fast.




It sounds like he might be a fan of trail braking into the corners (that will definitely keep the front loaded on corner entry!).


That's quite interesting. Did you ever have your 26mm bar on the car with the other pieces (torque arm and watts link)? If so, what were your impressions of it before you went back to a smaller bar?


OK, thanks. I'm at 191 lb/in in the rear right now, which is so close to 200 as to make no major difference. But my front is at 148 lb/in, which is a lot less.


Right. The nice thing, though, is that Filip is an engineer. He solves problems. If you want the car to have certain handling characteristics, he'll be able to come up with something that gives you that, as long as what you're after is within the reasonable realm of possibility.


So you're running 400 lb/in up front with JRI dampers, right? Previously, you were running 148 lb/in up front with the Koni Yellow dampers -- exactly what I'm running now. What's your impression of how the front end works over bumps and the like, especially in comparison with your previous setup? And are you able to adjust the height of the front to match what you previously had with the Boss springs and Koni dampers? I simply cannot lower the car up front any more than I have, because I wouldn't be able to get my car onto my driveway otherwise. But if the CorteX JRI coilovers can be adjusted that high, then they would be a possible upgrade path if I end up deciding I need more rate up front for whatever reason.

I have had several different Spring packages on the car searching for that perfect ride. with the Jri's at their highest ride height setting they are about an inch below stock. I get almost stock ride height by running 27.7 inch tall 275 40-19 tires in the front and 28 inch tall 285 40-19 tires in the back.

Now this is one of the other compromises that I've made. Handing purposes a 35 series Tire is of course much better. However, my car is a street vehicle on the worst streets of any metropolitan area in the United States according to the National Traffic Safety Association. And also according to me. I can't emphasize to you enough how horrible the pavement quality is around where I live and the potholes. I have blown out shocks ball joints and rims on the roads around my home. The taller tires are an absolute necessity not just for ride comfort but to preserve the equipment.

They do contribute to plusher ride quality though at the trade off of some vagueness in the steering wheel. Steering is still very direct but you don't feel the road as much.

 

[Norm Peterson]

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.

Took a while to put my thoughts together.


IOW, the problem isn't 3-link geometry per se but the constraints imposed by the S197's chassis not letting you put the chassis side pivots where you'd like to put them once you've substantially lowered the car. I get this, once having run the S197's 3-link geometry with the static ride height lowered a couple of inches. Basically, the OE geometry at OE ride height isn't all that bad, but once lowered you end up stuck with an unusually short and more variable SVSA as payment for having a reasonably stable A/S%.

For a little perspective, I've always needed my cars to retain street utility, with no more than minimal lowering (I absolutely hate the 'tucked' look that's become prevalent within the Pro-Touring segment), so I really haven't run into issues with trying to run rear suspension geometries, whether 3-link, triangulated 4-link, or leaf spring, because I'm not that far outside OE spec. And on street tires anyway, I don't see enough benefit from CG lowering in terms of either total lateral grip or resistance to rolling over to go ahead and lower what's still basically a street driven car for those reasons.

It crossed my mind when these torque arm threads first surfaced that big power was a major reason why the torque arm could have felt better to drive, at least with certain driving styles. I was hoping to coax something like that out into the open without - dare I say it here - leading the witness.

The reason I suspect that the TA might like a softer spring is tied to the timing of the various components of load transfer. Inelastic LT happens almost immediately, elastic LT last as the suspension finally reaches its new sort-of-steady-state position, while LT through the damping peaks somewhere in between. This is something you kind of have to think of on a tens to hundreds of milliseconds time level, much like the thermal and hydrodynamic transients I used to deal with as a stress analyst in the nuclear piping business. A driver may or may not be able to separate these things into the separate effects, but will feel the differences in transient behavior when the relationships among them change. Coming back to the TA and its springs, a high level of A/S% that rapidly increases in rebound plus a plus the firmer rebound damping that you'd use with stiffer springs also has at least a greater chance of transferring load off the rear tires too quickly. Drag racers talk of 'shocking' the tires with suddenly added rearward LT plus longitudinal force, and I suspect that the same holds true for extreme braking events. The tire isn't going to care which way the longitudinal force is building in.

I'd need a lot more power than I've ever had available in any car I've ever driven off the corners hard in a lower gear to feel like i need much more A/S% than the ~30% I've got now. Or maybe I'm just not stomping hard enough early enough on the throttle. At any rate, the car handles most inside curbings far better than I'd been led to believe from the various magazine reviews, and even running out onto exit curbings hasn't caused any pucker moments.

The weight issue is mostly a non-starter until you're chasing milliseconds at timed competition with contingencies at stake (which I'm not). If I was that worried, I wouldn't have shimmed the springs I just swapped onto my car on the axle side.

Here's a couple of screenshots, 3-link and TA, both with PHBs for lateral location. I've never bothered to plot SVIC migration, but the data is there to do so. Stuff that's been blocked out would only serve to confuse at this point.

As can be seen, my spreadsheet models don't allow for entering vehicle constraints, so they're purely mathematical in nature. I suppose something could be added, but I don't see the effort being worth the time as long as I recognize that most of the time there will be such constraints (on other forums, there are people who aren't the least bit put off by hacking up the floor and revising basic chassis structure to put suspension pickups where they need to go).

Norm

 

[Whiskey11]

I'm curious as to why you want roll understeer. I used relocation brackets to set up my car for slight roll oversteer, because it increases turn-in, prevents the rear from "crab walking," and makes the car "feel" smaller.

Do you spend more time in an autocross or on a track?

Cortex is focused around track cars and the stability provided by slight roll understeer can make for faster exits off the corner and more confidence in the car... in autocross a little bit of instability helps the car get around the course quicker... note: I'm not talking about prodigious oversteer, but with a little more willingness to turn in the car can get pointed in the correct direction to get through the course faster.

I, too, ran slight roll oversteer for that very reason... I also ran a seemingly stupidly high rear roll center and a pretty small rear swaybar (stock GT bar). The car was chuckable and put power down like a son of a gun. It also didn't completely wash out the front under power. I look at the things I did in that car and compare them to my current car and there are things my 09 could do that my 2015 can't... yet.

 

[NUTCASE]

This is great discussion in here.

Its true that its hard to quantify what makes a modification, or the price of a car worth paying for when we are talking about how it feels when you drive it. But there is no denying there is a market for it.

I think I am going to classify this the same way I classify watts link and IRS:

Can a torque arm be set up to work better than a 3rd link? .......yes
Can you make a damn good 3rd link setup for less than the price of a torque arm though? ....... yes


FYI I have owned 2 F-bodys and have worked on several more. I am a fan of the torque arm. But with my experience on the s197 it seems [similar to what I wrote above] you can make a damn good 3rd link setup, but if you want to be balls to the walls you can also do a torque arm.

 

[Sky Render]

Do you spend more time in an autocross or on a track?

Cortex is focused around track cars and the stability provided by slight roll understeer can make for faster exits off the corner and more confidence in the car... in autocross a little bit of instability helps the car get around the course quicker... note: I'm not talking about prodigious oversteer, but with a little more willingness to turn in the car can get pointed in the correct direction to get through the course faster.

I, too, ran slight roll oversteer for that very reason... I also ran a seemingly stupidly high rear roll center and a pretty small rear swaybar (stock GT bar). The car was chuckable and put power down like a son of a gun. It also didn't completely wash out the front under power. I look at the things I did in that car and compare them to my current car and there are things my 09 could do that my 2015 can't... yet.

I do mostly autocross. And this would explain why I've heard the comment from other people autocrossing my car that it is setup "better" than other S197s... that are set up for track driving...

 

[Norm Peterson]

I'm curious as to why you want roll understeer. I used relocation brackets to set up my car for slight roll oversteer, because it increases turn-in, prevents the rear from "crab walking," and makes the car "feel" smaller.

Having a little more stability at the end you don't have direct steering control over is your friend when speeds get higher and you don't always have a whole lot of paved runoff room like you do at autocross. In general, the transients aren't all on top of each other at the big tracks, and the whole concept of rear wheels that actively want to steer wide kind of scares me once when the notion of wet track sessions gets added to all that.

As mentioned, the amount of roll understeer doesn't have to be very much, and somewhere around 3% seems to be a pretty good place. 10% would be bad, and at much past that your car would flat-out hate slaloms. Especially in F-Street where you'd be on fairly soft OE springs and getting a lot of roll to get that big percentage of as wrong-end steering.

My own personal experiences with the 26 H&R swaybar on Steeda Boss Sport Spring mated with the Cortex rear end was not good. On corner exit I could not get any dig out of the outside rear tire because of insufficient weight transfer. way too much oversteer when ever I would try to put the power down. But with the Torsen there was a fun factor. Also the back end Was very stiff and non compliant and the ride quality was horrible.

Clearly too much roll stiffness back there for your driving style even if the ride quality hadn't been all that bad.

It doesn't take much change in rear bar stiffness to change the way your car feels. My own car, on 260f/220r springs has an unsettling little oversteerish twitch coming off the brakes into a corner with the rear bar set to its 185 adjustment that goes away at ~160 when that's the only change.


Norm

 

[Boone]

I used relocation brackets to set up my car for slight roll oversteer, because it increases turn-in, prevents the rear from "crab walking," and makes the car "feel" smaller.

I experience this "crab walking" sensation in corners. I can do a little throttle lift to help the car rotate, but it walks a fine line between rotation and snap oversteer.

It looks like relocation brackets may be an answer for me. I've been holding off tweaking my rear suspension too much since I just have adjustable spring perches, a LCA, and adjustable PHB right now.

I'm paying close attention to opinions and data in this thread.

 

[2013DIBGT]

In my car I've tried the factory 24mm, 20mm, 18mm and no RSB while using the full Cortex setup. I'm running 425lb F & 225lb R springs and an Eibach FSB.

With the 24mm bar I felt the car was pretty scary in terms of wanting to oversteer. Things got just slightly better with the 20mm bar but I still had several pucker moments that I felt I could live without. Next I ran with no RSB for quite a while and liked it for the most part; until I started hitting longer sweeping turns at higher speeds which also included elevation changes at the same time. In those situations the car felt a bit too "floaty" and slow to respond to steering inputs.

Being picky and still unsatisfied I decided to give an OEM 18mm bar a try out of a V6 Mustang (I believe). Once I put the 18mm bar in things started to fall into place but in doing so I also had to re-find the proper damper , ride height (.ie..Rake) and Watts Links roll center adjustments before I was satisfied.

I guess my whole point here is that having lots of adjustability is key to arriving at what you deem as being the right "feel" once all the wenches are put away. In my case if I didn't have lots of adjustability in all these other supporting areas I don't think I would have ever been fully satisfied with the car despite spending a small fortune on go fast parts.

I've had my share of Kits that came with predetermined, non-adjustable parts and not one of them was worth a damn the moment you start noticing the car doing things that even driving style adjustments can't overcome. Once you've encountered those situations its very hard to regain your confidence the next time around especially knowing that your stuck with the settings that helped to put you in that undesirable situation to begin with.

 

[modernbeat]

...I guess my whole point here is that having lots of adjustability is key to arriving at what you deem as being the right "feel" once all the wenches are put away...

You should amend that to say having both adjustability AND taking data. Even if the data is notes of the times and feel. But better data lets you make better decisions about making adjustments.

Back to the scheduled program...

 

[2013DIBGT]

You should amend that to say having both adjustability AND taking data. Even if the data is notes of the times and feel. But better data lets you make better decisions about making adjustments.

Back to the scheduled program...

You are correct of course, how could I forget to mention that damn spreadsheet I have

Not sure anyone is interested in knowing about all the scrap's of paper and ripped corners of cardboard boxes too which contain random scribblings that certainly made sense at the time; but not so much now