MicVelo

Perfect!! Check back for my next post (will post here in this thread) - it may help you make a decision on specific brand components. Later today most likely.

Thanks for helping to RAISE a rapidly diminishing signal-to-noise ratio here on the forum! Don't know if you've seen some of the zombie threads coming across here ("Waaaaah, I can't buy a Z cuz my credit sucks...." Oy....)

Mic

terrasmak

iTrader: (8)

I just want to mention that comparing string rates vs other cars is useless. If you knew anything about suspension you would be posting frequency (Hz) for proper comparisons. Frequency will account for spring placement, sprung and unsprung weight , where just spring rate is useless do to different motion ratios.

kilogram

iTrader: (1)

I was always surprised how low the Z's NF (natural frequency) was for how responsive it is. I calculated it out a while back and it came out to the 1.3/1.4Hz range stock F/R. Even most performance springs don't push it much above 1.5. For comparison, most track cars tend to target the 2-2.5Hz range. Farnorthracing has lots of good reading on the subject.

Carroll Smith seems dismissive toward frequency tuning. There's an online copy of Tune to Win here, the spring rate stuff starts on page 64 if you're down for some reading. Some of his stuff is a bit dated, I'll admit, but there's a lot worth reading as well. His stance on frequencies is that there are too many variables to make hard and fast rules. I think his position was based on the limit of computing power available when he wrote his books though. While I think dynamic chassis software is beyond the needs of the average enthusiast, frequencies are still a good starting point.

MicVelo

I was considering starting a new thread to give a few datapoints to others who may be considering suspension upgrades but this thread is most suitable as it discusses conventional "street" suspension.

So, a comparison between two of the most frequently discussed shock setups that don't have the words "coil" and/or "over" in the body of the posts.

Koni versus Bilstein on a Z33.

WARNING: This is LONG (cuz I talk too much). Veterans, pro tuners, racers, and others with working suspension knowledge/experience may want to skip this as there’s NOTHING new here. But it’s a single perspective on the two setups.

Brief re-cap/history leading up to this...

You take this old guy (well, not THAT old, but relative to the seeming average age of the forum's membership, ancient....laff) who’s owned about every genre of car under the sun and modified almost every single one of them for one reason or another, give him some free time and then you add in a long unrequited need for some lateral g-forces not experienced in a couple of decades (whilst doing the raise-a-family thing), you get a disaster waiting to happen, right?

Naaaaah, you get me. (OK, arguably a walking disaster. Hahahaha!)

Bought my Z33 ('03 Enthusiast) after buying my wife her Z34. "Waaaahhhh, whuddya mean I can't drive your car?" Had 67k miles, all stock, one owner.

Spent 6-8 months driving it as it was. Only "mod" during that time - if you could even call it that - was swapping out the comparatively chunky Touring/Performance six spoke alloys for superlight forged Track V.1s and a set of surprisingly-good-at-the-pricepoint Sumitomo HTR-Z3's in stock sizes (225/245 combination. (Great swap, by the way, lost about 7lbs unsprung at each corner.... huge difference in tactile response!)


This is where said Touring wheels ended up.

And to give you perspective on my type of driving, read this post. This is important because it gives a backdrop on what I expect from my cars and more importantly what NOT to expect. IOW, YMMV and it will, based on your own driving habits, skills, abilities, etc.

Summarized (so you don't have to read my other drivel... ), I do not baby my cars but I also don't abuse the hardware. No W2W, no solo.

Anyhow, after reaching the point of knowing exactly what I wanted changed based on its raw characteristics, I upgraded the suspension to achieve the following:

1. Reduce understeer at the limits - yes, agreed, more a function of lateral roll stiffness and tire selection but I had my reasons for also doing shocks and springs, below. I should note that the Z33 isn't a terrible, plowing beast (vis a vis so many other sports/GT cars fresh out of the factory made to understeer due to product liability issues) but for my personal taste and ability, I wanted to dial in a slight bit of oversteer. (Not a drift oversteer setup at all, just a well balanced dial-in that I could handle, given my use.)

2. Eliminate the buckboard ride quality typically associated with the early Z33 chassis. (Not horrible, mind you, but see further on why the ride quality was important in my suspension tuning criteria.)

3. Try to enhance steering input responsiveness WITHOUT steering mods (yes, again, more a function of "other" components and settings - tires, alignment, et al - but see next)

4. Enable my car to better communicate to me what the tires/suspension were doing while driving. This is related to #2 above, where the poor ride quality detracted or masked what the car was actually doing at any given point. For me a very unsettling feeling when pushing the car.

----------------

Set-up #1 BILSTEIN

Given the above, for my first suspension iteration, I went ahead and upgraded the basics: shocks, springs, anti-roll (sway) bars.

Components:

- Bilstein B12 ProKit “package” (Bilstein B6 Heavy Duty shocks mated with Eibach Pro Kit progressive rate springs tuned specifically for the Z33 (and it should be noted that the B12 ProKit is also available for many other cars, tuned for their specific chassis as well, e.g. BMW, Honda, etc) - See end of post for specific part number info)

- Hotchkis Adjustable Sway-bars - these are a chromoly tubular steel (well, I'm guessing it's 4130 chromo) design with leveraged adjustment - settings adjusted by changing the bar’s arm length (via the end link mounting points (4 holes front, 3 rear). Eibach, Stillen and others’ adjustable bars are similar design I believe.

Note: older Hotchkis bars were 3&3 Front & Rear, noted because you might run across some older used ones on the market in that configuration.

- Alignment settings following install were checked and found to be within nominal range (close enough to stock settings - 0-deg 35' Front, -1-deg 35' Rear) so no other components (camber adjusters) were added at that time.

Results of this configuration:

Personal non-scientific assessment: "Now that's what I'm talking about!"

Ride quality improved drastically. While the ride remains firm, it was much more composed and confidence inspiring. It's not "Cadillac smooth" by any stretch of the imagination, but compared to stock, the frequency of undulations and the jolting with road irregularities was virtually eliminated.

Rolling speed bumps now taken with a certain air of casualness (as compared to the nervousness with stock setup) – no crashing, jolting, bottoming. (Those horrific angular speed bumps are a whole ‘nother story though…. Doesn’t matter whether stock or lowered, those bad boys need respect… angular approach, slow up, slower even going down. Bleah.)

Given the Eibach springs being progressive, the street ride is civilized with good compliance within the first couple inches of spring deflection (compression load). That's pretty much street driving, folks.

Sidenote: And YES, to answer the other question in this thread regarding progressive versus linear springs, the Eibachs are true progressive design (and work that way) with the car's static load NOT coil binding them. If anyone’s keeping score, you can put these in the “true progressive” category. Laff.

Moreover, the Bilsteins earn/deserve their legendary reputation of yielding exceptional spring control while delivering a good ride without sacrificing performance at the upper limits.

In "Push It" mode, the car stays planted and level in all but the most extreme off camber turns. Even in those turns jounce/rebound control was good enough to keep the springs where they needed to be - without over compressing the outside or unnecessarily unloading the inside wheel. (I suspect that if I increase rear roll stiffness, however, that'd be a different story; but given that I stayed pretty conservative on tuning the side-to-side loading, OK for most applications.)

Overall assessment (at that time....): The BEST setup (for my needs) in all around driving.

Will say this on the economic front however: If the car’s use is limited to commuting/daily, Point-A-to-Point-B stuff, or you want a luxo ride, these (or the Konis) are probably not your best choice.

There are lots of OEM equivalent+ shocks out there that better suit those needs. (Tokico Blues, KYB GR-2s, etc all have good reputations and cost less than half what the Bils or Konis do). And please don’t think I’m dismissing them as “inferior” – I’m not – just being realistic that they aren’t in the same class as a set of the above. You DO get what you pay for.

----------------

Set-up #2 KONI

So let's say that I could have left well enough alone, totally satisfied with the handling, ride quality, and overall "does it well" stuff that comes along with a grand+ worth of suspension.

But then fate intervenes and along comes my numbah one son (never mind the only son) asking for my guidance on what to do with his car (an '06). He was going to buy some shocks that were, well, let's just say "within his college student budget".

“Uhhhhhh, son numbah one, I understand your plight but…. Oh, OK fine, let your old man take care of this for you.” So I let him talk me into giving him my Bilsteins. But... (I never showed my ulterior motive - don't play poker with me

This gave me the opportunity to do a couple things: do right by him and get him onto a "known/proven" suspension setup knowing that he'd eventually want to keep up with his mad skills at the wheel. (I sent him - and my daughter - to driving school long ago to keep them safer from the idiots on the road so, hey, I know he can handle it.)

But also, by giving him my Bilsteins, this gave me the opportunity to "try out" the #2 choice I had going into this suspension build, Koni Yellow Sports.

For purposes of evaluating just the performance delta between the Bilstein and Koni shocks, I kept the sway bar and spring set up baselined for consistency (left as it was with Bilstein setup - even kept the sway bar settings the same: hole 1 front, hole 2 rear for a bias towards oversteer).





Replaced in this configuration are the Bilsteins (with the Koni Yellows) BUT, to complicate things, I also replaced the stock rear suspension locating links and front UCAs (upper control arms) with SPC adjustable units. (Which, acknowledged, make this comparison a little more of a PITA to keep objective but it was necessitated by my thinking that "What the h**l, the suspension's all apart, might as well do it right, now.")





Why the SPC camber gear?

Few weeks ago, took the car out for some exercise and after some 80-90 miles in the hills and valleys out towards the Cali coast, I was detecting that "something wasn't quite right" (or maybe just "different than normal") with the handling. I knew something changed.

At first, I thought tire pressure stagger was off but I checked it next morning cold. 38/36 as I always run them.

So all things seemingly normal, took car in for alignment check and it revealed that my rear camber angles were outside of nominal range (negative).

Ummmmm..... WTF????

Only thing that I can surmise is that after the suspension settled into its new duties, the geometry got tweaked and was not something that we could catch on the first go 'round.

Now, if I drove 8/10ths+ all day every day (nice fantasy, eh?), the negative camber would be livable, but being that the car IS driven mostly on streets/highways, well, figured it was time for some adjustment to save my tires.

Gave me the side benefit, however, of allowing me to further tune what was formerly untunable: front caster, camber, and add/subtract additional toe if needed to compensate for any non-standard alignment settings and/or to give me a little more turn-in response when needed. (And of course, rear camber and toe correction are pretty obvious).

In other words, “Options”.

Anyhow, had the shocks swapped out professionally, SPC gear installed and everything buttoned back up as it was since I would need an alignment anyways. (And yeah, I got really lazy to do it myself again….)





Final alignment that I agreed upon with Rob (Z-Car Garage, San Jose) was his recommended setting of slight negative camber (front) to maximize all of the suspension gear) but to also save the tires from excess wear.

Straight up setting: -1-deg (F) and -1-deg rear.

Being that this car is mostly driven weekends and not a daily, a little negative camber deviation up front was a good compromise.

Immediately following my picking up the car, I took her on a short shakedown run up and back down Hwy 9 out of Saratoga, CA (see the other post referenced above). Not a long run but good enough to give me initial impressions and formulate a plan on making adjustments down the road.

NOTE: I do not have the proper gear to test for empirical data - no accelerometer, g-meter, fifth wheel, etc. - so this is all based on the patent pending MicVelo SeatOfPants-o-mometer and TwoHandsOndaWheel Tactile Response Gauge.

Assessments based on this short run:

- Koni setup IS firmer riding than Bilsteins (I had the shop baseline the shocks at medium-firm for initial testing and have made NO adjustments yet).

- Jounce-rebound control (at least on this limited first drive) seems about the same as Bilstein setup (at this point).

- Turn-in response is marginally improved BUT that's 90% from alignment, not the shock change.

- Ride height is lower by 5-6mm (~ -1/4") hub to wheel arch, which is in-line with Bilsteins' tendency to raise almost any car by that amount (on cars with lowered springs). Net result is that the Pro Kit springs are now at about the lowered height at which they are advertised.





The IF I HAD TO DO IT ALL OVER AGAIN Summary:

- Stock suspension - While it's pretty competent as is, you CAN improve it and I highly recommend doing so if you push your car because there is MORE to be had.

- If choosing between Koni or Bilstein with name-your-brand springset: You really can't go wrong with EITHER. (Yeah yeah, that's anti-climactic, I know... but facts don't lie...)

But choosing between them knowing now what I know, I'd go with Bilstein if my driving is street/highway/mountain-valley running (which it is). And I say that ONLY because of the ride quality difference. NOT on performance, as I consider them to be pretty much equal.

HOWEVER, if you do HPDE-track-solo as often as I drive mine in the hills, I would definitely recommend the Koni setup just for their adjustability to suit different tracks/venues.

This was pretty much the expected result on my part. Having run Bilsteins on at least a half dozen of my cars (Volvos, BMWs, MBZ), I knew what I was getting into. Koni, I've only run twice....once on my race car, once on a street driven S30 but it was enough to get the sense of them prior to this. In this respect, not much has changed.

So, be confident with either of them, they are the benchmarks of performance shocks.

Note: I wouldn't go so far as to say they are that much better than anything else but I will say (again) that "you DO get what you pay for." But switching between the two, either direction, nyet, not worth it.

What's next for this car? Not much. Might play with coilovers some day but for how I drive my car, see absolutely NO reason to do so. S'far as I'm concerned, I've now tried my two optimum setups and that's all she wrote.

Maybe my S60R would like a set of KW Variants one day...... Hmmmmm…. ponder, ponder… It (happily) never ends does it?

Good driving all.

Mic


Parts Reference:

Bilstein B12 ProKit: PN 46-190529

Individual (a la carte) Bilsteins

Bilstein B6 HD (Front Left): PN 24-118927
Bilstein B6 HD (Front Right): PN 24-118934
Bilstein B6 HD (Rear L&R): PN 24-118941

Bilstein B8 Sport (Front Left): PN 24-101561
Bilstein B8 Sport (Front Right): PN 24-101578
Bilstein B8 Sport (Rear L&R): PN 24-101585

Special note: as was pointed out earlier in this thread, the Bilstein B6 HD is good down to lowering of -30mm; Bilstein B8 Sport good down to 50mm. (Say bye bye to spoiler lips, exhaust components, and x-members. Laff!)

Koni Yellow Sport (Front Left): PN 8241-1216LSPORT
Koni Yellow Sport (Front Right): PN 8241-1216RSPORT
Koni Yellow Sport (Rear L&R): PN 8241-1217SPORT

zerofighter

Frequencies are used as a baseline but most race teams fall far away from it. And to tune the Z to have 2.5Hz your looking at a ridiculous front and rear rate.

Spike100

MicVelo’s message #64 is a great addition to this thread. That is practical and useful information.

As Mic mentions in his message, this thread’s title is “350z Street Suspension Upgrade.”

terrasmak

iTrader: (8)

I think I'm at 2.25 Hz front and 2.21hz rear right now. I would have to pull up my data and crunch numbers. Still a hair soft up front , rear is perfect as of now. To much front under dive under braking, and low speed corners.

Dam black art of suspension tuning. Next I'm trying out 16k front with my 6k rears

RobPhoboS

Great thread guys !
Thank crikey it didn't get 'noisy' in here

Z1NONLY

iTrader: (2)

What spring rates are you running now?

terrasmak

iTrader: (8)

I run 13k front and 6k rear. I have a set of 16k laying around. , that's why I'm going to try them

zerofighter

The reason why you're getting a lot of dive is because you're not at 2.25hz up front.

You should be somewhere in the 26kg will give you exactly 2.26hz up front.
Im assuming your running coilover spring in the rear. and in that case you need to be running 10kg and you will be running 2.1hz. If your running the spring in the stock location of course the rate will be siginificantly higher. Also do not think that the rear shock location is a 1:1 ratio, because it is not.

This is on a full bodied Z with 1000lb corner weights up front and 750 in the rear. With unsprung weight factored in. I dont know how you measured the frequencies, but your calculations are off. Even in a fully stripped out Z you wont be getting those target frequencies, at those spring rates.

zerofighter

16kg up front will give you 1.8hz
13kg is a 1.68

6kg rear on a coilover is 1.69hz
6kg rear in stock location is 1.3

Hope that helps.

MicVelo

Thanks, Spike. If it helps just one person make a decision they'll be happy with, happy to share.

terrasmak

iTrader: (8)

Motion ratio most have used for the Z is 0.68 front and 0.97 rear. I go off the weight of the car last time on scales.

Spike100

Mic… Great write-up (Message #64).

Question: Why did you replace the stock rear suspension locating links and front Upper Control Arms with aftermarket adjustable units?

MicVelo

Here ya go, Spike, class review since you fell asleep in class earlier.

Can't say I blame you. Hahahahahaha! Knew it was long but wow, when I went back to it, it was REALLLLLLLLY long.... and just to end with "Oh, you'll be happy with either." Oooooops.

-----------------------------------------

"Why the SPC camber gear?

Few weeks ago, took the car out for some exercise and after some 80-90 miles in the hills and valleys out towards the Cali coast, I was detecting that "something wasn't quite right" (or maybe just "different than normal") with the handling. I knew something changed.

At first, I thought tire pressure stagger was off but I checked it next morning cold. 38/36 as I always run them.

So all things seemingly normal, took car in for alignment check and it revealed that my rear camber angles were outside of nominal range (negative).

Ummmmm..... WTF????

Only thing that I can surmise is that after the suspension settled into its new duties, the geometry got tweaked and was not something that we could catch on the first go 'round.

Now, if I drove 8/10ths+ all day every day (nice fantasy, eh?), the negative camber would be livable, but being that the car IS driven mostly on streets/highways, well, figured it was time for some adjustment to save my tires.

Gave me the side benefit, however, of allowing me to further tune what was formerly untunable: front caster, camber, and add/subtract additional toe if needed to compensate for any non-standard alignment settings and/or to give me a little more turn-in response when needed. (And of course, rear camber and toe correction are pretty obvious).

In other words, “Options”."

Spike100

Thanks for the reply... But you never mention using the SPC camber gear to reset/refine your suspension.

What settings (camber, cast, toe) did you make/change with the SPC components? --Spike

RobPhoboS

I'm also going to have to go with some upper camber adjustable arms, to keep costs down I'm going with this:
http://www.driftworks.com/driftworks...ssan-350z.html

MicVelo

Hmmmm, wrote like a hundred pages and didn't mention the alignment settings?? Whoa, I'm realllllly slipping!

FRONT

Note: Before alignment (but with new adjustable gear installed and unfortunately don't have in front of me and don't recall what the settings were when I first noticed something amiss - not as far off but enough to justify my adding corrective gear).

LEFT FRONT -

Camber:
0.2 deg (Range -1.3-deg to 0.2deg)
Corrected to -1.1deg

Caster:
7.8 deg (OK, within range of 7.4deg to 8.9deg)
No correction at 7.8 deg

Toe:
-0.39deg (Way outside range of 0.0deg to 0.10deg)
Corrected to 0.07 deg


RIGHT FRONT -

Camber:
0.5 deg (Range -1.3-deg to 0.2deg)
Corrected to -1.0deg

Caster:
9.3 deg (Outside range of 7.4deg to 8.9deg)
Corrected to 8.6 deg

Toe:
-0.42deg (Way outside range of 0.0deg to 0.10deg)
Corrected to 0.07 deg

----------------------------------

REAR

LEFT REAR -

Camber: -1.2deg (OK, within range of -2.1deg to -1.1deg)
Adjusted to -1.6deg

Toe: 0.59deg (way outside range of 0.06deg to 0.14deg)
Corrected to 0.12deg

RIGHT REAR -

Camber: -0.4deg (way outside range of -2.1deg to -1.1deg)
Corrected to -1.6deg

Toe: 0.91deg (way outside range of 0.06deg to 0.14deg)
Corrected to 0.12deg

As stated, unfortunately do not have the "original alignment" specs just after discovering the settings were off (between the Bilstein and Koni swap) so I can't "blame" any particular aspect of the install for the whacko alignment because all the key stuff got changed and therefore was expected to be off. But suffice to say, there was detectable steering/attitude "weirdness" going on that I could feel prior. (I will look for that print-out and re-post if there's anything worth posting.)

New settings are made to give me advantage of the new shock/spring setup but also conservative enough to help save tires from typical negative camber inside wear.

Bottom line though - very satisfying driving the car and that's what's most important. While alignment is critical to real performance gains, I'm not one to split hairs and get all techie about it if it's working. And it is!

MicVelo

Looks good Rob, give us a report on how the work for you. Pretty good price! Jeesh, that's only about $240 USD! Compare that to SPC or SPL, whoa!