I'm having Tein 350Z H-Techs and Tokico D-Specs installed on my Sedan tomorrow and need some quick advice on the proper settings for the D-Specs. The spring rates on the H-Techs are 358/375 (F/R). How much firmer should the rear dampers be than the front? Particularly since I'm trying to eliminate understeer. Any experience and/or suggestions?

-T

 

i got another question...for the rear, how do you adjust the dampening of shocks? On my old car I had to use a screw driver for my tokico illuminas but that required getting to the top of the strut where you can actually turn it. Im think about Dspecs but im wondering how do people adjust it (i have no idea for our cars cuz ive never seen it).

 

There are several threads on this if you search....
The setup info from Tokico is pretty good, after that it's how you like your car setup..
Play with it.

 

Basically the same, except there's an adj tool that plugs into the top.

The premium sedans have a real bonus here, with the tilting rear seats...
You can get to the rears no problem.

 

^^ agreed. The common setup around here is 4F/3.5R. I'm running 3.5F/3R on RSRs with 350evo sways (F stiff R med) and it seems to be just about where I want it to be. A good starting point would be to start 5F/5R and adjust from there depending on your driving style.

 

[QUOTE=cyphrA good starting point would be to start 5F/5R and adjust from there depending on your driving style.[/QUOTE]I'm getting my Tokicos soon. 5F/5R is the standard setup. IYO, if I want a firm ride go with 4F/4R to start. FYI - I'm running the Tein 350Z HTech srpings.

 

I actually did quite a bit of searching but found very little detailed discussion of specific setups. And since I don't do the work myself, I don't want to have to take the car in for continual adjustments if we can nail the setup initially.

I definitely want a firm rear suspension with the front relatively softer, but I have limited knowledge of how damper stiffness should relate to spring stiffness. I'm assuming that the dampers should be "matched" to the spring stiffness, as opposed to trying to have them "create" additional stiffness. Since the 350Z H-Techs are already relatively stiff front and rear (358/375), I guess I'll try the 4 & 3.5 turns from full hard setup as a starting point, unless anyone has other suggestions. -T

 

I have a coupe so I can't really comment on the ability to get at the rear shocks on the sedan, but to adjust the rear shocks on a coupe, you have to unmount the top of the shock and swing out to get access to the adjuster. If you can get at yours by tilting your rear seats, then this will be a piece of cake for you. You definitely don't have to take the car in to get them adjusted. The shocks have a little screw-on dust cap that you'll remove (by hand) and then you use the supplied "tool" to turn and adjust the shocks. Literally will take about 5 minutes to do all four. I currently am running 4 turns from full in rear and 3.5 in front.

 

Actually im "creating" (term used above) additional stiffness for the front as i want to increase nimbleness and straightline stability...which wingnut got it
down using 3.5 F/ 4.0 R. that's a good setup especially when you have
swaybars set on a firmer setting on the rear.

this way you get more comfort going straight, then you transfer the
work to the swaybars when you turn.

 

I have 3.5 F / 4.0 R with OEM 2005 350Z springs on G35 coupe.

For coupe, you can order D-Spec cable-adjusters from Tokico, $30 a par. They are about 4” long and ½” in diameter. Above rear shocks there are already holes ¼” that needs to be ½”. I have mine under anchor cover on rear parcel shelf (6MT4me, Riffster, thanks).

Unrelated to subject, would front H-Techs with rear Z springs have any negative effect? 0.8” vs 0.5” drop in front? Other than perhaps cumber problems.

 

Not sure I understand this, kennybaby! How does a stiffer front suspension increase "nimbleness". Wouldn't the resultant understeer be detrimental to nimbleness? -T

 

that scares me a bit
but if he's concerned with "straight-line" stability then he's on the right track. still...like that thread I posted about suspension tuning, it suggests that "Single adjustable shock stiffer: Better turn in; better transient response; causes slower onset of over/under steer by slowing weight transfer depending on what end of the car is adjusted.
Symptoms of too much adjustment: suspension becomes unresponsive; ride gets harsh; car skips over bumps, loosing traction; Causes a big delay in weight transfer resulting in strange handling like under steer then late corner stage over steer."

so with that said, there is a compromise.

 

first, don't call me kennybaby.

second,
nimbleness is controlled by the initial bump (not mid to full compression)
setting of the front suspension. on the contrary, if your vehicle is
setup where the front is stiff vs the rear throughout the stroke,
the car will understeer as you said.

third,
The setup I have (if you checked out my other thread where I jot
down my entire setup of the car) shows that the rear swaybar
setting mandates over the front strut settings around mid stroke
providing mild to moderate oversteer bias which takes place starting at
around mid turn. the car does not understeer at all...actually i can't get
it to understeer unless i purposefully try to take on a 10mph hairpin at
45mph or something real dramatic where the tire capacity can't take
the sudden direction change.


Here's how the car responds in very simple terms...below are the
transitions:

1. straight line to turn in =
front initial bump firmness provides stability for front resulting in quick
initial direction change response (nimbleness). at initial turn-in, the front
does not stoke much because weight transfer is still not completely sent
to the front of the car.

2. turn in to mid turn =
weight transfer to front, rear sus setting mandates over front sus dampness
resulting in car turning without understeer as there is less weight in the
rear + stiffer lateral-g hold (swaybar). the higher rear spring rates also
provide added support to maintain rear posture while forcing the lateral-g
onto the tire sidewalls. from there, front/rear camber settings, throttle
input control vehicular hold and weight finally transfers to the rear tires
while exiting the turn through throttle input.

the 'abrupt transition' i mentioned after fiddling around with the damp
setting (where I edited my post) is exactly that. the front and rear
suspension strokes differently while the car is in motion as the weight
of the car moves front/aft or aft/front through braking and acceleration
changes. just because the front damper is set stiffer than rear does not
automatically result in understeer. you have to keep in mind the total
vehicle setting.

anyway, the above is a very nutshell version of how you setup a
car's suspension and why my car is setup the way it is. the reason I
always recommend adjustable swaybars and damp control is so that
you can dial in your entire setup based on your car's hardware and
your driving habits. hope some of the info helps.

 

are these high speed sweeping turns? or low speed high degree turns? harder damping rates are good for long sweeping turns, and easy to control in event of the **** sliding out. on tighter degree turns, you'd have to slow down a lot. your entry speed into a turn will be much higher, but will "push" unless you square out your corners by sliding the back end on deceleration. that's just my experiences on formula cars.

 

This fantastic info, kennyba....umm, I mean....kenchan! I'll need to find your thread (that you reference) to help complete my understanding. But since I now have adjustable sways (stillen) and will shortly have adjustable dampers (tokico) to go the Z H-Techs, I'd like to believe I can set the car up to behave more as I'd like. Basically, I just want to be able to drive like a "bat out of hell" without feeling like my car wants tip over and that I'm coming out of my seat around every turn. (In other words, I want it to handle like a sport-suspended beemer!) -T