Help me choose a suspension setup

Norm Peterson

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Plane of Chassis when RR is off the ground  and the RF is about to lift, outline rear view.jpg Plane of Chassis when RR is off the ground  and the RF is about to lift, outline side view.jpg I also took a crack at displaying the presence or absence of chassis twist. Within the limits of accuracy of my measurements (I do question a couple of them) and the ability of Excel to display a surface chart, there isn't much. You'd be looking for the front and rear lines in rear view and the right side and left side lines in side view to not be parallel to each other if the chassis was twisting enough to measure to within about 1/32".

View attachment 68904 View attachment 68906


Norm
 
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Norm Peterson

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I also ran an abbreviated test lifting from 12" forward of the RR jack point (with a 2x4 to spread the load. Instead of taking 6.75" at the rear fender opening to get the RF off the ground, it only took 5". So this is pretty sensitive to actual jack location.

I also have some idea how much the loaded sidewall height varies with inflation pressure (roughly 1/8" going between 25 and 35 psi, 285/35-18 tires on 11" wide rims).


Norm
 

Norm Peterson

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Minor correction to the 3D twist plots. Width is 72", not 62".

Yes, there is some chassis twist, but it's really small. Like a round 0.06°, which with a chassis stiffness of 21,000 ft*lbs/deg corresponds to an applied torque of about 1200 ft*lbs.

Initial chassis twist and chassis twist due to jacking.jpg


Norm
 

Pentalab

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So I made a few measurements today. Here's what happens at each corner as the RR is jacked up at that jack point (about 23" forward of the rear axle line). The LF goes down, all other corners go up. Tire sidewall heights reflect less load on the RR, RF, and LR, and more load on the LF, which is consistent with the chassis displacements. I checked at 2", 3", 4", 4.56" (when the RR lifted), and 6.75" (when the RF also lifted).

View attachment 68903


FWIW, my driveway is level within about 1/8" over the track width of an S197. The springs on my '08 GT are somewhat stiffer than OE (260/220) and there's a bit more bar stiffness as well. I suppose it's possible that softer-suspended Mustangs wouldn't lift the RF, but I'm afraid there isn't any easy way for me to check that.


Norm

I'm still trying to fathom how u ended up with just .058 deg of twist? And also same .058 deg, regardless of whether u lifted RR 4.56"..... or 6.75".

OK, put another way, IF you placed a digital level on the rear trunk lid, dead center...and it read '0.0 degs' , (no jack), what will the same digital level read when RR lifted 6.75" ?? Is it really 2.586 degs ? If that is the case, the digital level reading at front end of car should be LESS. You depict it as MORE...like 2.690 degs. Or am I reading this all wrong ? I'm talking about the level positioned so it's parallel to axle/ transverse to center line of car.
 

Norm Peterson

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Yes, I noticed the same things. The measurements are the measurements, except for the LR fender @ 4" which is suspect.

One thing is that jacking the car up isn't the same thing as applying a pure torque about the car's longitudinal axis. It's also possible that there's some sta-bar effect happening.

I may eventually re-run the sequence, but for its original purpose the measurements were careful enough to show that the actual twist due to jacking is very low.


Norm
 

Pentalab

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Ok, so what's the next step ? If that 6.75" could be reduced to 2" or less, with the use of SFC's, and your tests / measurement re-run, it would provide for some interesting observations. Then in part 2, test the sfc's out on the rd / hwy / local twisties /auto X / road course. Then perhaps some minor suspension tweaks, if required. Then re-evaluate.
 

eighty6gt

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OK, the car is level lifting it with a jack

that has little to no material difference on handling.
 

Norm Peterson

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Ok, so what's the next step ? If that 6.75" could be reduced to 2" or less, with the use of SFC's, and your tests / measurement re-run, it would provide for some interesting observations. Then in part 2, test the sfc's out on the rd / hwy / local twisties /auto X / road course. Then perhaps some minor suspension tweaks, if required. Then re-evaluate.
Not sure where I'm going to take this next, though I do have a couple of thoughts that'll at least make the measuring/remeasuring process easier and hopefully better.

With my springs and sta-bars, 4.56" is what it takes just to get the RR lifted free of the ground, lifting at the Ford jack point - that being defined by rear shock rebound travel. Rebound travel is a function of any amount lowered (I'm lowered somewhere around 15 or 20 mm in the rear, and there is 100 lbs or so in the trunk which is worth about another quarter of an inch). So I'd still need to lift the car at the rear axle line about 4.56", as currently loaded.


Norm
 
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Pentalab

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OK, the car is level lifting it with a jack

that has little to no material difference on handling.

It's not level ! He has to lift the RR 6.75" to get the RF off the ground. That could potentially affect handling..and probably does. I'll comment on the handling part..after I install the steeda jacking rails..and welded into place. The rear steeda box tube / frame braces are already installed and welded. Well welded at 2 of the 3 corners of the triangular rack. We will weld the 3rd corner this spring. Steeda's 2" wide x 1.5" tall 4130 CM rectangular tubing jacking rails are bolted with 2 x bolts at each end. The game plan is to also weld the rect tubes, on the inboard side..on the edge..in about 5 x places. Ok, now it's my idea of solidly installed.

To keep the finish intact, a hockey puck placed dead center on my low profile floor jack may well do the trick. A puck is 1" tall x 3" diameter.
 
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Norm Peterson

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It's not level ! He has to lift the RR 6.75" to get the RF off the ground.
That 6.75" applies only when lifting at Ford's jack point. Move the jack one foot further forward and you only have to raise the RR fender opening up 5" (I ran that one). Move the jack point as far back as you can (risk being on anybody who tries this; I have not) and I'm sure you'd have to lift the fender at the axle line 7" or more.

This would be related to handling when encountering a road surface that's sort of 'warped', where when even going dead straight ahead the crossweight percentage would not be the same as when measured on a flat surface. Jacking could be considered a crossweight problem, taken to extremes.


To keep the finish intact, a hockey puck placed dead center on my low profile floor jack may well do the trick. A puck is 1" tall x 3" diameter.
That's one of my little tricks . . .


Norm
 

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I will be installing the Steeda X, 555 5093 brace so I can keep the rear seats intact. I will have a review after my next track day at WGI. I have hard data from last year's event (lateral G force, and lap times) to compare with. Stay tuned....event is a few months away still..
 

Pentalab

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Finally got a Fedex tracking # for the steeda X brace and the pair of Steeda jacking rails. WX still sucks, so this will have to wait a bit.
 

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My Steeda jack rails and torque box braces are still sitting in the box. will bolt on for starters then have welded in when I find someone that knows what they're doing....
 

Juice

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Steeda X brace is installed. The bolt-in install is pretty easy, but drilling is required. Without fully welding the brace in, I dont think it offers much additional chassis stiffening. The lower 2 mounting points just go under the upper shock bushings. I will run it as-is before I make a decision on welding it in.
tmp_6937-IMG_20190324_130144928-1340397254.jpg
 

Pentalab

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Finally got my steeda jacking rails installed yesterday. They come with elongated holes at both ends.... and of course, mine had to be elongated a tiny bit more. Steeda X brace was not installed. After taking a lot of measurements, I would have to do a lot of creative, precise cutting to make the X brace compatible with my existing, welded in steeda rear stb. So X brace sitting in basement shop for now. Also had a pinion seal leak so got that sorted out. Steeda rear stb comes with a pair of mounting plates, that fit over the rear shock mounts, and extend straight down on the aft side, and also the inboard side of each shock mount..which is where they get welded. The actual rear stb is adjustable in length, and rvs threaded on one end. Spherical on each end too. With the mounting plates welded in from yrs ago, it makes for a real pita to climb in there to take precise measurements. Issue is that steeda uses a pair of welded ribs / gussets that interfere with the lower ends of the steeda X brace. IMO, I would be too likely to get it wrong, making the required precise cuts to make the 2 items compatible.

If the steeda rear stb was in the shop, not welded in, then I could calculate / measure a precise cut + fit between the 2 x items, but as is, head 1st into the trunk is no fun.

The steeda jacking rails are 2" wide by 1" tall, CM rectangular tubing. Aft end of each jacking rail, overlaps with my existing steeda CM torque box braces, sharing the same 2 x bolt positions. After driving aprx 6 miles across town, it feels a lot different. Its feels like a lot of weight has been removed. I can throw the car all over the road. The handling has definitely changed. It's more than a subtle difference too. I wasn't expecting this at all. The primary function of the jacking rail install, was just to make swapping wheels / rubber a bit easier each spring..and fall. Car still has the 235mm Nitto Motivo's on it, which is what I use for fall / winter rain season.

I'll do a more exhaustive handling test today, while the 235's are still on.

On friday, I will swap to the 285 front / 305 MPSS rear setup. Then repeat the handling tests. I have a theory why the handling changed right after the jacking rail install, but it's just a theory for now. Nothing else was changed, and max neg camber is still dialed in using the steeda HD adjustable front strut mounts...+ a very slight toe out.
 
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JJ427R

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^^ I'm anxiously awaiting the results with the other tires.... still amazes me they guys who never try em' say they don't do anything or are just bolt on do dads, if they only knew.
If myself as a paraplegic can feel the big difference, I can only image what someone who has the "in the pants" feeling is going to notice....

Rock on Pentalab!!! This made my day so much you don't even know....

p.s. after my Ford Performance hood struts I just received, Jacking Rails will be the next install on my new 2018....
 
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Pentalab

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I got the 285-40-18's installed on the fronts...and 305-35-19's on the rears yesterday. I shifted the jacking point 6" further aft of the steeda re-enforcing plate. The fronts were quite a bit off the ground before the rears lifted just off the ground. But I only have the front lowered 1/2"..and the rear is lowered
1.25". A couple of years ago, I sheared off the roush pass side strut (monotube)..so replaced both front roush struts with oem struts. The Roush struts are 1/2" shorter than oem..( measuring from bottom of strut to spring perch). Roush get's 1/2" front drop from their shorter ( and one helluva lot stiffer than oem) front struts...and the remaining 1/2" drop from the Roush front lowering springs. The roush front monotube struts work great.....on smooth roads, but are a bit too stiff for some of the shit side streets in town. I could push as hard as I could on either front fender with both hands.....and get zero deflection...ditto with me sitting on either front fender..with my meager 150lbs. With the shit roads here and there, that's what eventually did in the right front roush strut. Now I have more compliance in the front end..and 1/2" higher...which is better for my street use. I still have to crawl over speed bumps..at 1-2 mph.... move forward a bit, then repeat with the rears. (eng was lowered 1/4" years ago with the steeda eng mounts, at the same time the JBA LT's were installed...so the CG is lowered a bit).

Now the limitations are the oem leather seats and oem 3 point seat belts on my 2010. I'm getting thrown side to side...but I also had that b4 the jacking rails. With the jacking rails ( and previously installed mating steeda tq box braces..which were welded in a few yrs ago), it doesn't lean in corners. It's not a subtle difference either, it's blatantly obvious.

Just to re-iterate, the MAIN function of the jacking rail install was to make life easier for the twice a year wheel swap, that's it. The way more than subtle improvement in handling is something I was not expecting. I took it for 3 good rips last night, it corners flatter. It feels like the power steering was increased by 60%..even at low speeds, baffles me. I can throw it all over the road. This is the best it has handled so far...even vs the stiffer roush front monotube struts from a few yrs ago. I also have the added weight of the roush M90 blower, + 145 lb auto tranny, 2nd tranny cooler, front stb, and 4 x braces beneath the eng. Roush front + rear sway bars, 37mm front / 26mm rear.

The eaton tru-trac LSD + whiteline watts link were both installed (on the same day, years ago)..along with the 1 piece DSS-DS.

Jacking rails are a simple install, but a 2 post lift can't be used.... only a drive on lift. My already elongated holes had to be elongated a tiny bit, to fit. I also have a BMR rear tunnel brace installed, (1/4" thick plate)..which bolts in the middle, between the pair of steeda rear tq box braces. That entire mess forms one homogeneous brace from extreme left to right.

The jacking function works superb.... but the unexpected handling improvement is a bonus. The naysayers can psychoanalyze all they want to. An engineer buddy of mine who works at Los Alamos,
said there is a sign at nasa that sez......"one test is worth a 1000 opinions". The sign has been up since day one. I never have forgotten that. Any versions of these rails are cheap. The steeda version is a simple bolt in affair. The BMR + KB versions are weld in only, and a lot more bracing with their double, parallel rails.

The pair of steeda CM jacking rails were $118.00 last Jan 2019, on sale. That's the best $118.00 I have spent yet.... it's a huge bang for the buck.
 
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redsnake

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Look, I could be part of the crowd of people "tell you what you want to hear", blow smoke up your backside... but that's not who I am. The reality is: those bolt-on braces and trinkets are good at one thing on the S197 chassis: adding weight. People like to validate their purchases online, always - this this is just a false portrayal, some self-affirming feeling they need to express to legitimize their choices. This is what 90% of forum comment are based on. ;)

The truth is: there is no data to back up these claims.No scientific testing, just "feelings" and lots of things you can buy.

There are simply a lot of semi-useless parts on the aftermarket made to relieve you of your money. Entire companies are built around this practice. I've heard from some of the folks slinging these parts, after confronting them on their chicanery: "Well if we didn't make this stuff, someone else would. And their money is green!"

Bolt-on doo-dads promising a "better ride" by giving you a stiffer chassis? Come on... think about it. That's just not how cars work. If the OEM's felt they could improve ride and/or handling with doo-dads, don't you think their multi-billion dollar engineering efforts would uncover these tricks? But some yahoo with a welder... no, HE has it figured out.

We all need to be mindful of the folks slinging miracle parts. Be skeptical, and know that a big portion of this industry only cares about taking your money. You will notice how I am not pushing this OP to any parts we sell in this post. Not a single thing, because what we make is not appropriate for his needs.



The OP is asking for isn't really what the "Corner Carving Racing Tech" sub-forum is about. But I'll attempt to give him useful advice, not validate Bolt On Ballast ideas.

1. The 3500 pound S197 is more similar to an E92 BMW than it is not. We work on lots of both of these cars, and I've driven many dozens examples of each. What he is missing is more likely tied to an a tire and wheel difference than anything else. The OEM tires on the S197 are SUPER tall sidewall Mud and Snow rated garbage. The OEM tires on somehting like an E92 M3 are orders of magnitude better.

NOTHING we do to our cars makes more of a difference in PERFORMANCE and RIDE than the tires we outfit them with. NOT. ONE. THING.

Upgrade to better rolling stock to get what you are looking after, not steel ding-dongs and tubular braces.

2. Tramlining is 75% caused by alignment, probably 25% cause by tires. Take out any front toe (zero) and put new/name brand tires on and inflate them to proper pressures and that all likely goes away.

3. If you want a good ride for "street driving" don't buy any of the cheap coilovers or shocks out there. Get something OEM appropriate, new, and hopefully monotube based. Bilstein, if you can find them, might be a good place to start.

Good luck - and STAY SKEPTICAL,
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
 

Norm Peterson

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The way more than subtle improvement in handling is something I was not expecting. I took it for 3 good rips last night, it corners flatter.
"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.


... 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.

I'm not trying to claim that you didn't feel what you felt. Just that you're insisting on assigning credit where it does not belong. Unfortunately, I can't give you the engineering attitude or experience that you'd need - and you do need some of each - in order to even know why you're misplacing credit here. It's frustrating, and somewhat insulting that a legitimate degree and nearly 40 years experience is being taken so lightly. Never mind the 30+ years of occasional self-study in vehicle dynamics.


Norm
 

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