Matt's pursuit of Suspension and wheels

[shogun32]

Just got my car back from Performance by Jax who handled the installation of a laundry list of upgrades. Fantastic fellow and a clear lover of Mustangs. He has an eclectic set of customers - saw a 1955 Ford Ranch today that had been retrofitted with a recent Cobra dash and drive line, by Jax.

This was the workorder:

• Whiteline differential bushing
• BMR IRS brace with bushing lockouts (CB762, CB010)
• use Steeda alignment bushings (Delrin) to fill IRS cavity

• Steeda spherical bearing into lower control-arm
• Steeda rear vertical link (Polymer)
• Steeda k-brace
• Baer 2-piece rotors (lightly used)
• Bullitt brake calipers (red, from OP Mustang)
  • Ford/Ferodo DS2500 pads (OEM)
• Steeda brake lines - flush/replace brake fluid with Motul 600
• Steeda front swaybar
• Steeda end-links
• Steeda roll center correction control arms

• Steeda pre-assembled Pro-Action shocks with dual-rate springs

• Steeda Tri-Ax shifter with bracket and transmission 'bushing'

• Borla/Ford 'street' exhaust with black tips
  • wrap 'diamond' bends before and after differential with Heatshield Armor
  • install Steeda H-pipe instead of Borla resonator

• BMR jacking rails
• Steeda clutch spring assist

I think that came out to around $3500 in parts.

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[shogun32]

ed: should have read this thread first.

I've had the Steeda Pro-Action (adjustable) with dual-rate springs on for an hour. For sub-40mph regular road driving, especially the rear is entirely too 'busy'. Not bouncing down the highway like slammed ricer Civics, but borderline objectionable. (I need someone with a chase cam)

The stock suspension was decidedly soft in both directions (comp, rebound) and 'floated' across undulations. Now I'm feeling a slight bit overexerted in the visual complex. Like how you feel 'tired' after a long drive when having to focus.

Once wicked up on one of my 'interesting' back roads the 'hopping' feathered out and the significant reduction in brake/accell chassis pitch (as well side to side) was very noticeable and welcome. The suspension 'thumped' over small pot holes and such without putting the energy into the chassis like the stock used to do.

My initial diagnosis is that I have a harmonics issue. I'm at 1.25 turns back from hard at all corners and I'm not sure if I'm transiting the dual-rate zone or if more/less rebound damping and at which end will settle things down. That's the problem with tunable suspension, you have to try various things. My guess is 1/4 less rebound front, 1/2 less rear.

My opinion may change in the future if I can get the damping to cooperate, but I think Steeda might want to change the 800/1200 transition point so it's mostly an 800 spring and only in heavy loading it transitions into 1200 lb/in rate as opposed to the current which is mostly a 1200 spring and downgrades to 800 as the inside wheel gets light. That or be more insistent that the dual-rate springs should be reserved for track duty. I may need to get some linear 200/800 or try the BMR SP083 pair. But I'm getting ahead of myself...

 

[shogun32]

Talked to Steeda and where I had set the rebound was bang on where they say to start.

Drove for a couple hours today in my favorite ramps and back roads. The nose of the car was being pulled down over the backside of undulations so it's pretty clear I need to loosen things up a bit. And hitting various square-edged bumps the response was a little too taut. Good suspension is supposed to disappear beneath you without being vague and remote. Going over the same roads that G-out with the PP1 rear shocks, still compressed a healthy amount but didn't launch the back of the car on the way back up. Very nice.

I gotta say my SS/1LE is going to have a fight on it's hands in the handling department now. One place where the SS would shudder transiting from banked to cresting and into a negative bank, the Mustang just drove ahead. Neither of the muscle cars are as much as fun as the GTI on that complex though because you can stay in the throttle and let it slide a touch as it scratches for traction. Front drive and 600 fewer pounds sure is fun.

The Steeda shifter support is an absolute MUST DO. Sloppy, amorphous "lumpy" shifts are now (albeit also with the help of their short-throw rod) very tactile and "mechanical'y" - it feels like you're putting your hand inside the transmission and grabbing the shift forks directly. Lovely sensation. But it is a 'raw' sensation vs factory "inoffensive smoothness". It's pretty close to how the Tremec 6060 in the SS and GT350 feel, but is more "crunchy" than the Tremecs which sometimes leave me wondering did it really go into gear?

If you're in habit of leaving your hand on the shifter, installing the transmission bushing and shifter support bracket will cause the knob to vibrate. It's not objectionable really but you can tell there is something mechanical under your palm. There is also now a subtle growl from the transmission tunnel. The exhaust (even as quiet as mine is) is much louder but if you want to pretend you're in a silent interior (what's his face in Lincoln ads) the trans bushing is not recommended.

 

[shogun32]

As part of the Stop-the-Hop kit I had picked up the Steeda diff bushing lockout kit with it's choice of 2 hardness 'pucks'. But then I decided to pursue the Whiteline total-replacement bushing solution since they are 70 shore in hardness which is a few ticks below either of the Steeda options as well as BMR's, and half the price to boot. However the install is a lot more involved so any cost savings are quickly negated by shop labor.

I was concerned about noise and you can discern a background growl but I'm going to need more time to see if I can differentiate between trans and diff. It doesn't interfere with conversation and my radio volume is no different than it was before all the work. I also got a couple of thunks from the rear end where the stock car was silent. I think that has to do with the massive vertical links and the huge spherical bearing in the lower control arm.

If you replace your IRS bushings with something solid then I'm sure you'll get an earful of differential grind in the cabin. I used the BMR 010 and 762 kits and augmented with Steeda's Delrin alignment bushings.

Driving it is a revelation as many others have previously observed. There is no hinge in the car and it feels as solid as if there were 8" C-channels running fore and aft.

 

[shogun32]

Mike at Steeda reached out to assist with my initial observations. This level of consumer engagement is definitely rare if not unique. MAJOR props!

The short and long of it was 1.25 turns back (out of ~2 turns possible) from full stiff might work in the summer at the race track (but their own drivers don't go that high either), but definitely not at sub-50F on the street. I will be testing at full soft and should hopefully arrive at an optimum setting within a half turn of that. Also the needle is very sensitive so 1/8 turn changes is worthwhile.

With the car sitting flat, there is only about 3/16" (5mm) of travel before the 1200lb/in rate kicks in - basically as soon as the car starts to roll the higher rate resists further motion. Given this and the bleed circuit needle positions in common use, I still contend a couple of shims should come out of the rebound stack (or a lighter oil, different needle taper) and the spring probably should have more like 1/2" and maybe as much as 5/8" of 800 rate before it transitions. But then I would need to put some linear potentiometers on my shocks to datalog behavior and hire race-winning professional drivers to tell me, "No, you're wrong!"

Steeda does have to find a solution that's broad enough to cover most of the use cases and driver preferences. They test their stuff constantly, have been at this for 40 years, and rack up the wins. So what do I know...

I guess my current summary on this is that if you want to use the Dual-rate springs and the Pro-Actions, be advised that maximum road-course performance is the focus of this setup and it may not take too kindly to cold or DD usage patterns.

I'm eagerly looking forward to the Pro-Active setup on my EB.

 

[S7N]

I would have loved to of tracked my EB before I sold it the front in is so much lighter on that car and it really makes a difference in the corners. If I could I would of kept both.

 

[shogun32]

I have no idea how running the Steeda pro-action at full soft is tolerable. I'm at 3/4 turn out from hard (1 turn in from soft) for the front shocks and only now does it behave. The rear I'm at 1/2 turn in from soft and it very clearly needs another 1/2 turn or so.

I figured I owed @SteedaTech an update as well as the forum. I cranked in another 1/2 turn on the rear shocks so now I'm sitting at ~3/4 turn out from full hard (closed) - BTW that is the ONLY correct way to measure where the needle actually is. NOW the car is much more balanced fore-aft and no longer annoying to drive. I was chasing apexes on undivided 2-lane and some nice scenic byways NW of Culpeper VA and then back home by way of US211 for about 4 hours. It's definitely still quite sporty but the pogo-stick is mostly banished. I probably need another 1/8 turn on the fronts. If you run this Steeda setup I strongly recommend you start with 1 turn out from seated from the start.

IMO the Steeda dual-rate front springs are way too high rate for street use.

I still stand by this assertion. The hood moves upward too much in response to lesser bumps - ie the spring force is too high so instead of the wheel moving, the entire chassis is being pushed upward.

@Bluemustang pointed me to a nifty video that talked about getting the frequency balance right.

And I believe @Brian@BMVK (?) also documented it in his spread sheet (google Docs) and it shows why the BMR SP083 spring set is "so right".
BMR SP083 = F1.63 R1.72 1.05
Steeda Sport Linear = F1.46 R1.55 1.06
vs
Steeda DR = F1.93 R1.9 0.98
Which has the bias going the wrong direction. The F=SP083 R=DR rear should approximate F1.63 R1.8 1.10 which is rather more than I would like to see. A 280-300 spring in the front is probably better. In any event I am MUCH happier with my car's dynamics tonight than any time in the past. I'm fast becoming a believer.

hat tip to https://www.drtuned.com/tech-ramblings/2017/10/2/spring-rates-suspension-frequencies

 

[Norm Peterson]

Couple of thoughts . . .

It probably doesn't matter all that much whether you reference your damper settings from full-firm or full-soft as long as you pick one and stick to it. That said, if you expect to be adjusting upward from an initial setting - this generally being the preferred approach - I'm going to make a case for referencing your settings to full soft. Adjusted that way, as you crank the damping up any backlash in the adjusting mechanism is going to remain "taken up" against any tendency to drift "softer". You should still be returning to your end point reference every time you change your setting.

Interesting flat ride video. I was itching for him to go just a little further with damping and how that also affects flat ride behavior. FWIW, flat ride involves more than just the frequencies and their relation to each other. Wheelbase and road speed also enter into the numbers, and the next step after that involves damping.

Damping does a couple of things to that whole front and rear frequencies/vibrations thing, the obvious one being that the front and rear suspension oscillations tend to decay over time. The not-so-obvious one may come as a surprise - damping actually lowers the frequency from the undamped numbers. Only a little at first, but it's a progressive effect as the amount of damping is increased, and part of the reason why flat ride considerations become relatively less important as cars approach becoming unstreetable all-out race cars is that suspension frequencies as vibrations get damped out pretty quickly and there isn't enough pitch rotation left to make for much front-to-back head toss (think old pickup truck with bad shocks and nothing in the bed on a smooth-bumpy road for what head toss is like in the extreme).


Norm

 

[shogun32]

That said, if you expect to be adjusting upward from an initial setting - this generally being the preferred approach - I'm going to make a case for referencing your settings to full soft.

except "full soft" is an artifact of the assembly technician and will vary. Full hard is mechanically repeatable every time and denotes a known location. The adjustments on these are quite hard to turn - I'm used to snick, snick of a rotating drum on a detent which these most definitely are not.

 

[Bluemustang]

The issue IMO is the balance of the spring rates. The hood bouncing you're talking about "porpoising" is most likely due to the ride frequency relationship front and rear and the shocks not being enough to properly control.

IMO if you need spring rates near 250 lb front and ~1000 lb rear and should target a ride frequency relationship of 5-10% higher rear. Couple that with a quality monotube damper (like the Ridetechs or FP/Bilstein if you don't go coilovers) and you'll be in business. I don't think the Steeda ProActions can adequately handle the DR springs for what you are looking for. To achieve the level of dual-sport purpose that you are trying for (ride and handling), you need to match your spring rates better and get better dampers.

The flat ride technique is real and many OEMs use it. Not only does it make it ride better but it will handle better too because it settles quick and the car is ready for the next event.

 

[Bluemustang]

I figured I owed @SteedaTech an update as well as the forum. I cranked in another 1/2 turn on the rear shocks so now I'm sitting at ~3/4 turn out from full hard (closed) - BTW that is the ONLY correct way to measure where the needle actually is. NOW the car is much more balanced fore-aft and no longer annoying to drive. I was chasing apexes on undivided 2-lane and some nice scenic byways NW of Culpeper VA and then back home by way of US211 for about 4 hours. It's definitely still quite sporty but the pogo-stick is mostly banished. I probably need another 1/8 turn on the fronts. If you run this Steeda setup I strongly recommend you start with 1 turn out from seated from the start.


I still stand by this assertion. The hood moves upward too much in response to lesser bumps - ie the spring force is too high so instead of the wheel moving, the entire chassis is being pushed upward.

I would disagree here that it is the spring rate that is too high... it's that the dampers can't properly handle it and also the ride frequency proportions. You can run stiff springs and still have it ride good, IF your dampers are good enough. You're limited with what you can do on the Koni style twin tube dampers. It just won't control it the way a monotube coilover unit would.

 

[shogun32]

Here's my copy of the rate and frequency spreadsheet.
https://www.dropbox.com/s/yytkee6jlsmvofj/s550 mustang springs.xlsx?dl=0
All the cells are 'live' instead of being static values. I don't know where the original's corner weights came from nor the equation used and thus my frequency numbers are a little different. But the principle still holds.

 

[shogun32]

I would disagree here that it is the spring rate that is too high... it's that the dampers can't properly handle it

Maybe. It's also entirely possible that the slow-speed comp is shimmed too tight (or too much preload) and so approaching 'rigid' and it takes rather more force to break the orifices open and oil to flow. I'm watching the hood movement before the rear goes over the same bump so ok, maybe it's not fair to blame the spring just yet but rather the damping. I need to rip the shock apart and see how it's shimmed and dyno it. That will tell me if the shim stack is at fault or the spring is. My money is on the spring though, not to say the damping couldn't stand to be improved.

There is nothing inherent to 'twin-tube' being inferior to monotube except that the piston diameter will necessarily be a bit smaller (approx 8-10mm) and thus port size will be smaller as well and has fewer options. I deal with 20mm and 25mm pistons and admittedly going to 'mono' in 30mm opens up a lot of options and max flow rates. But piston size is primarily a high-speed compression issue.

 

[shogun32]

I wish I had the time to play with https://www.penskeshocks.com/product/piston-vdp-linear-2/ but I may just have to look at the Ohlins or RaceTech catalog for a suitable piston once I get eyes on the internals.

 

[shogun32]

IMO, get the Ohlins R&T with custom rates through hotpart.com, get 300/1200 and call it a day.

and another $3000 while trying to offload what I currently have. Buy cheap, buy twice...

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