aleok

iTrader: (1)

so the a higher spring rate more likely to cause premature wear to the D-specs then springs that drop a significant amount?

knight_white99

iTrader: (5)

More likely wear will be due to the kinds of roads that you drive. If you drive very bumpy roads where the shock has to do a lot of work, you are more likely to see wear than if you drive on smooth roads all the time.

Just because you have springs that cause a larger drop doesn't guarantee more wear if the shock is not working hard, provided that the shock is still within its normal stroke range.

aleok

iTrader: (1)

Do you know the stoke range for the d-specs?

Gsedan35

iTrader: (10)

It's not just a stroke issue, it's walking a bit close to the envelope of deminishing returns, aka shock underdampning. I love D-specs, but having driven 2 car's with them where they were set at over 1/2 way up they total stiffness range on OEM spring rates, I'm mightly leary of anyone running them past their own engineer's recommended rate range. Biggest thing I doubt has to deal with shock control in the real world, meaning off track. You can have the finest bit's and pieces, but if you shocks do not have the ability to deal with a bumps or undulations mid corner, your ability to carry speed is done. The only possible saving grace that I can forsee for the D-specs is their ability to also adjust compression dampning. But tying in my own ride and drive, I just don't see those last 3 clicks of adjustment range allowing proper control on spring rates that are almost 60% higher then oem. Notice that I have never ever posted a review of my Koni coilover setup, insuffecient bump travel and not enough rebound range and I'm not lower then a Z at oem ride height! When it's smooth as glass I absolutely love them, but that's not realistic.

By the way, D-specs have the same stroke range as oem Z shocks do, so do my Koni's.

knight_white99

iTrader: (5)

Let's start by saying that I am an engineer by profession. Albeit I am a nuclear engineer, not a suspension engineer. But we nukes are basically mechanical engineers with a specialty area. I spent many hours as a student solving differential equations involving springs and dampers, so I think I understand the physics and math behind these items fairly well.

That said, I can't stand underdamping either. Most cars come with suspensions that are sadly underdamped and often oversprung. That's why I was not a fan of the D2 Racing coilovers for anything except dead smooth pavement. They were completely underdamped at even their most firm setting. They would bounce several times coming into corners under hard braking and unload the back end of the car -- very disturbing when you are trying to slow to the exact speed for corner entry, and heaven help you if you hit a bump in mid corner.

That said, I am very impressed with the D-Specs. On the track, I have never needed to run them at more than 1 turn from full hard (i.e., I have never used their complete range of dampening adjustment). So even for competiton purposes (I am now running some serious time attack events), I have yet to use their full dampening capability, even with the Tom springs that I have now.

I have a fair amount of track experience, some with poor equipment and some with good equipment, and the way that the D-Specs behave is impressive for the cost.

Let me give you an example. At Cali Speedway, there is a big bump right at the kink coming onto the main part of the front straight. If your shocks are not doing their job, you will hit that bump, unload the suspension, and maybe spin off the track if your foot is full on the throttle, so you have to back off of the throttle there. But with the D-Specs, I hit the bump, the car did it's one bounce and immediately dampened out the bump, allowing me to maintain a firm tire contact patch and I could keep my foot planted on the floor from the time I exited the last turn until it was time to brake at the end of the straight. So, the shocks did exactly what I needed them to do - dampen out the bump so that I could maintain firm tire contact with the ground.

Read what 350ZNV had to say about how his car handled at Cali Speedway with his JIC coilovers and his 12K springs (way too bouncy), and then read what he said about my car (very well setup):

https://my350z.com/forum/autocross-road/176063-redline-time-attack-fontana-3-5-06-a.html


The stock shocks were actually not too bad, but the D-Specs allow you to tune front and rear and even side to side response, which is invaluable to me on the track. Are they perfect? No, not perfect. If I had $5K or $6K to blow, I would get some Motons. But for $500 I am getting a pretty darn good shock that has served me well for over a year and doesn't seem to be phased by any spring combo that I have thrown at it. I would love to be able to adjust compression dampening and rebound dampening independently, but that is just not going to happen in a shock in this price range.

As I noted before, for purely street use, I would not recommend the Tom springs with these shocks. The Espelir springs are a great compromise though, and if my Z were mainly a street machine with occasional track use, that is what I would be running. But now that my Z is mainly a track machine and occasionally a street machine, I am pretty happy with the Tom springs. I might even order some custom Swift springs in the same diameter and rate but a little shorter to gain some more range of height adjustability with the collars.

97supratt

iTrader: (61)

Has anyone tried the D-specs with tanabe G210's? Also, how do you guys adjust the rear shocks with the strut cover over it?

overboostedtoy

great write ups! thanks guys

changsw

iTrader: (2)

Hey, did you have to get new shocks because you installed the springs? I have the same springs, but I'm on stock shocks. They feel fine for now, but I'm wondering how long my stock shocks will last with the Espelirs.

Nano

iTrader: (1)

Great review Knight. (I have the D-spec on order with their linear springs, hopefully the behavior will be similar to what you have, albeit less "hardcore")

are you still on the OEM sway bars? and how much are you dropped? (sorry if you mentioned it somewhere, I missed it)

knight_white99

iTrader: (5)

Thanks, Nano.

I expect that the D-Specs will work fine with any spring that is within their intended target rate range.

I am currently running the Hotchkis sways, set full stiff front, medium rear. I don't measure drop, I measure ride height from the ground to the center of the fender wells (a straight line measured vertically through the center of the axle). Currently, I am at about 25 3/4" front, 26.5" rear (give or take 1/4" side to side). That's pretty low, and I often scrape the underside of the car just getting out of my driveway. I wouldn't recommend that low for a daily driven street vehicle for that reason. I only have about 3" of ground clearance to the lowest part of the underside of the car.

On the track, my ride height is actually about 1/2" lower, since I run 17" wheels and 275/40 tires all around. But this seems to work well for me given the stiff springs. Also, I have Cusco adjustable front upper a-arms, set to almost 3 degrees negative camber. Again, I wouldn't run that on the street, but it aids turn-in on the track quite a bit.

Everyone has different needs and in theory will require a different optimal setup, so I don't suggest trying to duplicate my setup. The weight of the car and the distribution of that weight (my car has the extra weight of a roll bar, but some reduced weight elsewhere), your tires, and even your driver weight (I am not small at 6'4" and 230 lbs) will impact optimal car setup. Even running a full tank of gas versus 1/4 tank can significantly alter how the car handles. It's all about finding a good compromise.

Hopefully, you can find a setup that works well for you. I still haven't completely optimzed my setup yet. I have yet to corner balance the car. However, the collars of the Tom Motorsport springs will ultimately allow me to do that. That may change my ride height somewhat as well.

Nano

iTrader: (1)

yeah, sorry for the layman's term, should have known better from your sig.

I track the car as well (not as seriously...) and was concerned about the tokico on the track. Great to hear you are pushing the limit on them and are having success.

Except for my softer spring rates, my car is not arranged much differently. I am running the tokico 375/375 springs(didn't find anything better at the time) 17" wheels with a staggered setup 255/40 - 275/40 and stillen sway bars. Everything is sitting in garage, haven't had the chance to test anything. Still need spacers for front wheels and a few other accessories, but hopefully it will be a nice difference from stock and a start to work forward from.

had no clue about colars and tom motorsport springs.

overboostedtoy

how's that Tokico springs? would you consider writing a review? I'm thinking about getting Tokico springs w/shocks combo. They lower about 1.25 in. all around. Are you scraping over bumps or coming out of driveways? what about the rear alignment since I'm not considering getting an alignment kit; are you able to get the rear toe in spec w/o alignment kit.

Nano

iTrader: (1)

sorry, nothing installed yet

I'm currently in europe and will be back toward end of this month. I have track day mid may, will write a review when everything is up and running.