Help me choose a suspension setup

[JJ427R]

My car corners flatter as well Norm, I've had guys follow me on track tell me that, and others on here have said it as well. You can deny all you want and give all the theories you wish, after all they are just "your thoughts"
I look at your videos and I can see your car roll in the corners, way more than you will notice it my car in my videos. I suppose that is all some sort of video illusion your going to give me a page analysis on.
Until you try one on your car nothing you say about it really matters. It's your loss, not ours!

 

[Pentalab]

... yet another attempt at substituting subjective impressions (that weren't even instrumented) for a detailed analytical look at what's going on mechanically/structurally. What you, or I, or anybody else feels is not a substitute for understanding what's going on physically or mechanically. If it was, Ford could hire anybody who passed high school physics straight from H.S. graduation into an engineering capacity.



Norm

Whoa. I just finished re-reading the entire 15 page thread.... and did not see the above paragraph. Where did it come from ??

 

[JJ427R]

As much as Norm hates being disrespected about his 40 years in the business, it's just as disrespectful for him to tell us what we feel in our cars isn't what we are really feeling?? I cannot believe the arrogance of somebody to do that.

 

[Norm Peterson]

My car corners flatter as well Norm, I've had guys follow me on track tell me that, and others on here have said it as well. You can deny all you want and give all the theories you wish, after all they are just "your thoughts"

If it really does corner flatter on the track after you did something than it did before you did it, that was because you were either cornering at slower speeds or because you stiffened the suspension (springs, sta-bars). Or increased the vertical spring rate of the tires (different tires or increased inflation).

Shocks & struts would limit the amount of overshoot during transient maneuvers, which might be interpreted as "less roll". That's the closest it gets, and this part does not apply once the car has taken its set.

I look at your videos and I can see your car roll in the corners, way more than you will notice it my car in my videos. I suppose that is all some sort of video illusion your going to give me a page analysis on.

You'll have to provide some actual cornering g's along with your car's spring rates and sta-bar rates before that has any meaning. I mean, if you're cornering at 0.9 lateral g's it's not going to roll nearly as much as it would if you were pulling 1.25 g or higher. I have datalogged g-measurements for my car and from spring and bar stiffnesses, so I know about where my car is in that respect. I even have the ability to estimate how much roll your car should be seeing. Probably within a quarter of a degree, which is below what you'd ever notice "by eyeball".

Until you try one on your car nothing you say about it really matters. It's your loss, not ours!

I've probably said before that I would fully expect it to feel a little different. And I'm not trying to make you feel like you spent money unwisely either - if it makes your car feel better to you at speed that's all you need.

But it's not going to make the car roll any less or accomplish anything that can't be accomplished with different springs, sta-bar settings, or shock/strut settings if you have adjustable dampers.


Your loss is in your refusal to acknowledge the value of engineering evaluations. The amount of roll that happens in a corner is something that can be calculated, and it can be determined that the contribution of jacking rails to that amount of roll is negligible. Tell me, do your outside observers actually notice the amount of twist that's occurring along your car's chassis while your car, their car, and them in their cars are all moving around at least a little from the braking and cornering forces?


Norm

 

[Norm Peterson]

4 wheel independent suspension is far superior to a 3 point s197, The KR suspension is great, made mt GT500 (S197) drive way different. kev

Only if the IRS was thoughtfully designed and engineered. Just having IRS/4-wheel independent suspension means nothing if it wasn't done up right.

IOW, IRS can be better than a 3-link/PHB, but it doesn't get there simply because it's IRS and not a stick-axle.

I've driven 4-wheel independently suspended cars that weren't all that good, at least one of which was of more recent vintage than you might think.


Norm

 

[JJ427R]

If it really does corner flatter on the track after you did something than it did before you did it, that was because you were either cornering at slower speeds or because you stiffened the suspension (springs, sta-bars). Or increased the vertical spring rate of the tires (different tires or increased inflation).

Nothing was changed with my springs or anything else. Only the added combination of Matrix Brace and Jacking Rails, still stock Roush Sport suspension even after 55,000 miles and over 25 track days....

Your loss is in your refusal to acknowledge the value of engineering evaluations. The amount of roll that happens in a corner is something that can be calculated, and it can be determined that the contribution of jacking rails to that amount of roll is negligible. Tell me, do your outside observers actually notice the amount of twist that's occurring along your car's chassis while your car, their car, and them in their cars are all moving around at least a little from the braking and cornering forces?

I have no loss, I gained 2 seconds on the track immediately and the feel of the car in corners changed considerably, that's a win in my book any day.
You are the only one losing anything by not trying them yourself, but then again, your loss on the track is somebody else's gain....

 

[Norm Peterson]

Nothing was changed with my springs or anything else. Only the added combination of Matrix Brace and Jacking Rails, still stock Roush Sport suspension even after 55,000 miles and over 25 track days....

I'll have to see if I can find some stiffnesses. My car right now rolls about 1.8°/g in the suspension plus about another 0.6°/g in the tires (due to lateral load transfer compressing the outboard tire and relaxing tire compression on the inboard side). There really isn't a lot of room for improvement.

I have no loss, I gained 2 seconds on the track immediately and the feel of the car in corners changed considerably, that's a win in my book any day.

Of course it's a win. But the win is in the new "feel" making you much more comfortable at speed, which you're trying to ignore completely.

You are the only one losing anything by not trying them yourself, but then again, your loss on the track is somebody else's gain....

Maybe I'd notice a gain, maybe I wouldn't. Honestly, roll doesn't bother me nearly as much as it seems to bother other people. Even the amount in the picture below (yes, that's me driving it) isn't something that ever got my attention, I just drive to what I can get from the tires.

Norm

 

[JJ427R]

Located below is a link to quite a number of professional pics of my car in different corners at Road America last July, look at my car and compare to the other similar stangs in my run group or even cars in the same photo, you will easily see a difference in how my car sits on the corners.

https://www.photosbyedmund.com/NorthwoodsCobra/Road-America-2018/76-718-Group-3/427/

 

[Pentalab]

"Corners flatter" is a function of suspension stiffness, not chassis stiffness. They aren't the same. At best, and this is a stretch, your seat mounting points might not be moving quite as far, which you could consider to be your seat "rolling" relative to the car chassis due to of your weight sitting in that seat. But all that's influence there would be your perception. Chassis roll at the front and rear axle lines would remain unchanged. I'm not going to chase down a link to the chassis twist measurements I made a while back, but I do remember them as being truly minimal and not subject to being made much smaller no matter how much more stiffness was added. And that's with somewhat firmer suspension tuning, which would have exaggerated the observed results slightly.
Norm

I suspect that any increase in stiffness (esp torsional) may well enhance the effect of the front sway bar. Increased torsional stiffness would mitigate font end flex in the vert plane. I may well be wrong, but I don't have any other explanation for the effect I'm seeing. Nothing else was changed.... except the addition of the pair of jacking rails. ( yrs ago, I installed a pair of steeda CM front sway bar support tubes, each tube is aprx 14" long. Whiteline makes their own version...and both versions are only for 05-10 cars).

I have one of these 8" long, combo digital / bubble levels..which is also magnetic. Back lit as well. I just tried it 10 mins ago... and it fits like a glove in the center of the dash, in that recess designed for the Boss-302 gauge package. This is on 10-12 cars. Dunno if it will fit on other year cars or not.

Reads in .1 deg increments. There is also a button to 'zero out' the display. IE: drive down a road that's not flat, sez - .4 deg. Zero it out, and it now reads '0 degs'. That's a moot point for now.

I'm thinking, with a passenger in the car to keep an eye on it, Readings could be taken, either at a fixed speed around turns..or at a fixed G rate. IF the car corner's flatter, the digital level should reflect that effect. At least it would provide for an all important, additional data point. Dunno if .1 deg resolution
is fine enough for meaningful data..or not? I'd have to temp tape it down really good to be of any use..easily done though.

Too bad I didn't think of this several years ago..or even a week ago. Useful data points.... but nothing previous to compare to. In an ideal world, a digital level with say .05 deg increments, or better yet, .01 deg increments might just resolve some of this debate.

 

[Norm Peterson]

Pentalab - you'd also need to know how much the roadway itself is cambered (yes, camber is term that is applied to the road surface in highway design as well as to wheel alignment). IOW, if the road or track is cambered by 2° down to the inside, your car is cornering at 1.00g, and rolls at 2° per g, the chassis will be sitting perfectly level as a bubble level sees it. If you look at the last photo on page 1 of JJ's photo link, you can see how this works.

Here's my car in a corner at 1g or a bit more per datalog. Not nearly as much roll as JJ is suggesting. Feel free to find any distortion along the chassis that a pair of 1 x 2 jacking rails could even start to reduce. Take as much time as you want; I doubt you'll find any.





Norm

 

[JJ427R]

 

[OX1]

Interesting list here.

http://youwheel.com/home/2016/06/20/car-body-torsional-rigidity-a-comprehensive-list/

Chevrolet Corvette C7 (2014 – ) 14,500
Ford Mustang 2005 21,000

Who would have guessed that one............

Funny a Cruze is double a C5....

 

[Norm Peterson]

I suspect that any increase in stiffness (esp torsional) may well enhance the effect of the front sway bar.

I think you're almost on the right track. But the front sta-bar stiffness is what it is and is not increased by adding jacking rails. What the jacking rails may or may not do is increase the amount of moment being resisted at the front vs at the rear.

Keep in mind that chassis stiffness affects roll moment distribution to the rear as well as to the front. Turns out in this case a little less roll moment is attracted to the front - which actually makes the front roll a little less with the rails than without them. It's the rear that's more affected, a little more moment and a little more roll.

We're talking about such small numbers that for all practical purposes even if the rails added 20% to the chassis torsional stiffness there just wouldn't be anything to see and even the TLLTD is remaining virtually constant. And given that the model I'm using assumes that all of the sprung weight is located at the CG rather than being distributed along the entire length of the car (a much more complicated analysis), such numbers (provided below) get lost in the coarseness of that assumption. But as crude as it is, it's still better than trying to quantify uninstrumented visual observations.

The difference in chassis twist if the rails added 20% to the 21,000 ft*lbs/deg OE stiffness is under 0.001°. Less than one-one thousandth of a degree. The changes in roll at the front axle and at the rear axle are of similar magnitude.



To JJ, you really ought to be OK with a 2 second lap time improvement coming solely from the car feeling subjectively better. Even on a good day with little other traffic I bet you're seeing over a full second variation in lap times with no changes made to the car's chassis or suspension whatsoever. Even two seconds would not surprise me.


Norm

 

[Norm Peterson]

Just so you guys know, I did baseline the above analysis against some K&C data provided for a S197 Mustang as reported in Car and Driver some years ago. Roll per g I got was within a quarter of a degree per g of what some really fancy test equipment actually measured. I'm good with that.


Norm

 

[Pentalab]

Pentalab - you'd also need to know how much the roadway itself is cambered (yes, camber is term that is applied to the road surface in highway design as well as to wheel alignment). IOW, if the road or track is cambered by 2° down to the inside, your car is cornering at 1.00g, and rolls at 2° per g, the chassis will be sitting perfectly level as a bubble level sees it. If you look at the last photo on page 1 of JJ's photo link, you can see how this works.

Here's my car in a corner at 1g or a bit more per datalog. Not nearly as much roll as JJ is suggesting. Feel free to find any distortion along the chassis that a pair of 1 x 2 jacking rails could even start to reduce. Take as much time as you want; I doubt you'll find any.

View attachment 69593



Norm

If the road or track is cambered by say 2 degs to the inside, that can be factored into the equation. Either drive through it real slow, or stop every few feet, take measurements, then either factor it in.... or simply use the 'zero out' feature. Ok, say it is a consistent 2 degs..and we then zero the reading out. Take the corner at speed, and at 1G, it should read aprx + 2.0 degs. Or don't zero it out, then it should indicate...0.0 degs. Moot point really.

Norm, your calcs / software/ analysis may be on track / correct, but it still does not explain the effect that both myself and jj427r are seeing. This is not some subtle difference either, blatantly obvious that something somewhere has changed.


"I suspect that any increase in stiffness (esp torsional) may well enhance the effect of the front sway bar."

"I think you're almost on the right track. But the front sta-bar stiffness is what it is and is not increased by adding jacking rails. What the jacking rails may or may not do is increase the amount of moment being resisted at the front vs at the rear.

Keep in mind that chassis stiffness affects roll moment distribution to the rear as well as to the front. Turns out in this case a little less roll moment is attracted to the front - which actually makes the front roll a little less with the rails than without them. It's the rear that's more affected, a little more moment and a little more roll."

.................................................................................................................................................

Norm, your comments above is what I was alluding to. With the jacking rails installed, and say taking a sharp left hander, the front sway bar now has the entire left side of the car to contend with....and not just the left front portion.

In my case, the front ends of each steeda jacking rail has a flat plate welded to it, with the flat plate facing inboard....(90 degs to the 2" x 1" CM jacking rails) These flat plates terminate on the same pair of oem bolts that secure the oem cross brace, located behind the eng. Back end of each steeda jacking rail, also has a flat plate welded to it, but this time, in line with the jacking rail. Each aft end plate is then sandwiched between the 'steeda tq box brace'...and inboard side of pinch weld. There is 2 x oem threaded holes to bolt the 2 x steeda items together. These pair of threaded holes on each side were for the rear oem convertible support braces, used on all verts.

The steeda tq box braces are a cm triangular affair, with corner #1 terminated on the front end of each lca mount ( 2 x bolts + welded). Corner #2 is well inboard, welded onto inboard longitudinal member.
Corner #3 has a piece of channel steel welded to it..and terminates ( 2 x bolts + welded) to the aft end of the steeda jacking rail plates. I also have the oem cross brace that ties the back end of the K frame together, plus a BMR A arm brace, that ties the front A arms together. Roush 37mm front sway bar...and a pair of steeda front sway bar braces..... + a steeda front STB over eng..and steeda eng mounts..with their stiff durometer mounts.

Steeda rear stb (welded) in trunk. Roush rear 27mm sway bar. BMR rear tunnel brace, located between the inboard pair of #2 corners of the steeda tq box braces...(forms one continuous brace from extreme right side of car to extreme left side) . Roush lowering springs front + rear, and roush monotube shocks. ( + DSS-DS / whiteline watts link / Eaton tru-trac).

Point here is, in my case, with the recent addition of the pair of steeda jacking rails, it's now one continuous brace...from eng cross brace... straight back to the front end... of each rear LCA mount.

The addition of the CM jacking rails appears to be the final missing piece of the puzzle.... now tying the rigid front end....to the rigid back end of the car. The entire affair is pretty damned rigid. You folks can call it placebo effect, confirmation bias, pseudo junk science, or anything else you care to. I call it..."something has changed overnight...and it's more than a subtle difference". Local ford dealer only has two drive on lifts, and both were tied up....so my car stayed inside their shop overnight. I pick it up the next day, after lunch, drive 6 miles home, and wonder what the F#@K just happened to my car.

 

[JJ427R]

I'm with Pentalab on this. I've stated since this started on another thread that the difference the Jacking Rails made on my car, in conjunction with the Matrix Brace, is way more than subtle, it is a huge difference. Mine are all welded in and I still fully believe it's one of the most significant changes you can make to the handling of your car. Pentalab also could not believe the difference, just in a short 6 mile drive. The difference on track, as I stated before, is even more significant. Others who have installed them have stated it as well. Can't deny true testing by users over some generated numbers. Also remember, we've still have not had anyone come on here who installed them that said they didn't work, we've only seen those who have not tried them that said they won't work.

 

[Racer47]

I installed them and they work very well.........for jacking up the car. They didn't do anything to improve handling. I'm running 315 A7's, 600 lb fronts, 250 lb rear and am faster than most and have raced for over 30 yrs.

As I said before. If you're happy, thats fine. But its not real.

 

[Pentalab]

I installed them and they work very well.........for jacking up the car. They didn't do anything to improve handling. I'm running 315 A7's, 600 lb fronts, 250 lb rear and am faster than most and have raced for over 30 yrs.

As I said before. If you're happy, that's fine. But its not real.

With your 600 lb front springs, and mating front struts (presumably optimized for the massive spring rate)
I'm not surprised. Roush front springs are only 20-30% stiffer than oem, and only provide for a 1/2" front drop. So it amounts to kinda an apples to oranges comparison. In my case, I had em installed for ease in jacking up the car...twice a year, that's it. I wasn't expecting any handling improvement, or very subtle at best. What I got instead was a rude awakening.

Just for the record, 2 yrs ago, my right front Roush monotube, (far stiffer than oem/ rock hard) strut sheared clean off..... so replaced both front Roush struts with new oem struts. That softened up the front end quite a bit. That also increased the ride height by 1/2".
(Roush front struts are 1/2" shorter than oem.... from bottom to spring perch). Some of the local roads around here are real shit, and careful as I am, they did in my strut. Roush struts were superb on the local hwys, which are smooth. I could push as hard as I could, with both hands, on the front fenders, and could not get em to deflect downwards..same deal if I sat on the front fenders with my 150 lbs. On anything less than perfect roads, it was a rough ride.

For $118.00, for the pair of jacking rails, they work, good enough. If I can perceive less roll, without having to resort to heavier springs / struts, that's good too. Less roll + smoother ride. It's just a street car these days. I can't begin to fathom what 600 /250 lb springs would feel like.
Racer 47, how much are you lowered front + rear ?

 

[Racer47]

The reason I listed the spring rates is because stiffer springs should exaggerate the effects of any chassis stiffening. But the jacking rails didn't effect handling at all, even with the stiff springs.

I don't know how much I'm lowered. It hasn't been stock for so long, that I don't know what stock is. Its low, but not slammed. Its lowered as far as I think I can go and still have enough suspension travel. Its this low..... wanna race?

 

[759-OR]

47,

Can you tell me how your handled your rear bump stops with that setup?

I have the FRPP units with the tops cut off. But wanted to see how others were handling that.

It seems you have probably experimented and thought it through.

Thx