Cujo159

iTrader: (3)

EDIT: This started off as a discussion seeking information about AST true coilovers, however, it's evolved into a true coilover discussion for the 350Z.

WARNING: Technical Information Inside. Unintelligent readers beware.

Does anyone here have AST true coilovers for their Z? If so, what model is it, what is your spring rate and damping?

Thanks Guys.

Cujo159

iTrader: (3)

Bump for responses.

terrasmak

iTrader: (8)

That is basically a Motorsports grade damper, spring rates will be what you pick, dampening with be set to your spring rates. Springs will typically be chosen to go with your tires.

Cujo159

iTrader: (3)

Yea i realize that. I got the car set up with a true coilover style already on it and want to keep it like that for ease of set up and alignment. My other options are very limited as must companies don't manufature true coilovers for the 350z as not enough people buy them. And the ones that do Stance, BC etc. aren't of the quality that I'm looking to have for perfromance (driving around town, autox, track days). I have Stance GR+ on there now with 14k and 7k F/R Swift Springs and I know it could drive better than it does in that set up.

It would also cost me about 700 bucks to return to a stock config as I don't have the OEM parts.

terrasmak

iTrader: (8)

You should be able to use your swift springs, just call AST and let them know you want to configure them as true. Basically the same I did with my Motons

Cujo159

iTrader: (3)

Yea I've already been in contact with them about that. My springs i think are too stiff to give sufficent traction on imperfect roads. Right now I already have an interesting time with it kicking the rear end out under light accel with very tight cornering. AST quoted me 600 for the front and 300 for the rear for a good neutral set up.

terrasmak

iTrader: (8)

I run a 700 front and 336 rear , works great with 285/35 RS3 front and rear. The combo you have would probably be great for an NT01 combo with 275/35 front and rear.

Cujo159

iTrader: (3)

The biggest issue I'm having is hooking up, either from a dead stop, or going around a low speed corner (aka stop light, go take a turn). I keep getting slippage under any type of throttle response. I'm thinking the suspension is too stiff with springs at 14k/7k and it's not allowing for enough movement for tracktion. I'm also running RE11's and don't know much about the tire but I'm not too pleased with them so far.

Thoughts? As you track your Z and handle high and low speed turns regularly I'm very interested in your exeriences in this. Thanks!

terrasmak

iTrader: (8)

The difference between 5k and 6k is huge , I have a slight problem getting out of the tight stuff with 6k ( but the car rotates much better ) I bet your spring rates are killing you. I run wider tires with full aero and have less spring rate. Something to think about.

Also , what are your sways set at , I have Hotchkis bars, rear at full soft and tempted to drop to the stock rear bar so it's 80% softer

Cujo159

iTrader: (3)

Yea it's quite annoying. The set up I have from buying it was put on there for "stance" purposes so I'm left with the task of having to make it better lol.

So your springs are 700/336 in/lbf (?) front rear correct? And that equates to what in metric?

My sways, being cusco, are not adjustable. So they are set at "**** me" right now lol.

Cujo159

iTrader: (3)

BTW do you have true coilovers or the OEM set up? If you have true, have you seen any wear and tear from that set up that would otherwise not happen with the OEM set up?

Cujo159

iTrader: (3)

I'm also looking to get gsedan35 in on this discussion. how do you get him in here when his inbox is full?

ttknf

Try a "visitor message."

stuartc323

Here you go bro, got it from the EVO forums

kg/mm to lbs/in
-----------------------------
16 = 896
15 = 840
14 = 784
13 = 728
12 = 672
11 = 616
10 = 560
9.0 = 504
8.5 = 476
8.0 = 448
7.5 = 420
7.0 = 392
6.5 = 364
6.0 = 336
5.5 = 308
5.0 = 280
4.5 = 252
4.0 = 224
3.0 = 168
2.0 = 112

So terra is running 12.5kg fronts and 6kg rears

what are u using the car for? serious tracking, Double duty, or DD?

There shouldnt be any real wear and tear as long as your spring rates offset and front to rear roll rates match you will be ok, if this is off you could risk your tires wearing out early, no traction on daily driven streets, poor cornering, off balance car roll, etc..

here is a good article by Gsedan35 on true coilovers and matching spring rates and roll rates

https://my350z.com/forum/brakes-and-...ock-dynos.html


Honestly you have to wait for him to bestow his knowledge or search, if he sees a topic starting to get out of hand with improper info he steps in, you have been getting good info from terrasmak, a very knowledgable person on the forum on all kinds of performance set-ups so ur good.

terrasmak

iTrader: (8)

Currently i have 12.5 front and 6k rear, for a tighter course i may drop back to my 5k rears. Next TimeAttack i will have 13k up front and the 6k rears, see how it works. As mentioned, the stickier the rubber, the more spring you need, also aero (wing, splitter ) will need higher spring rates. I run RS3 285's front and rear and an APR wing with a full splitter. Test , test and test, i have done a lot of it.

First thing i would do on your car, disconnect the rear sway bar, just remove one endlink, drive and see how it feels. Next if needed, probably will , call Scott and NissanRaceShop.com and order some Swift springs 12k front and 5k rear.

BTW 12k and 5K with a true coilover rear is equivalant to the Nismo T2 race springs. That is why i started with that proven combo. T2 race is 690lb front and rear in the OEM location.

Great reading, most crosses over from autocross to the roadcourse http://farnorthracing.com/autocross_secrets.html Steve Mitchell suggested it to me, a lot of it was Greek to me at first.

Cujo159

iTrader: (3)

Yup figured that out just after posting lol. Thanks bud.

Thanks bud. I knew it was a mass/distance unit of measure but I couldn't get a straight answer of the specific units that are used as standard to do my own conversion.

I'm using the car for double duty DD/track & autox but I enjoy precision driving on a daily basis

The wear and tear I'm worried about is with the shock tower mount locations taking the full weight of the car as opposed to splitting the duty between the shock and spring location. Unfortunately I don't have any OEM hardware to switch back to.

Yea I read through that. Being new to suspension theory it was a little over my head but I'm reading through it again to get a better grasp over it. But in short I know it basically states not to buy Fortune auto lol. Hence why I contacted AST for the possible True Coilover purchase.

Thanks terrasmak. Have you seen any metal fatigue at your mount locations in the rear with your true coilover set up? I assume you don't have any extra bracing inside or outside the car at the shock tower locations to mitigate this (yet?).

The tires I'm running are RE11's so they aren't too sticky, but the reviews that they've receive I feel like they should stick a lot better than they have been. The whole set up is definitely not idea for rain either.

Why is the T2 set up 690lbs front and rear? Did they purposely pair very stiff springs in the rear with softer effective front rates (moment reference effectively dividing the front rate by 2) or does the oem rear geometry in the rear cut the effective rate in half as well?

terrasmak

iTrader: (8)

No fatigue or anything on those mounts , have not heard of anyone with that problem yet. Mine will be braced when I install a full cage later.

Motion ratio is close to the front , will post more info tonight on that. I know I have posted a bit of stuff on "wheel rate " search for it for now

terrasmak

iTrader: (8)

Front Motion ratio 0.688 with a 690lb spring , you will have a wheel rate of 327lb

Rear motion ratio 0.649 with spring in OEM location with a 690lb springs, you will have a wheel rate of 291lb

Rear motion ratio of a true coilover conversion 0.97 with a 280lb spring you will have a 263lb wheel rate. The 336 lb spring i am running now, gives me a 316lb wheel rate.

The stiffer the spring, the less traction you have. You want to run the softest spring you can, and the softest sway bar setting you can for the tire you run.

ProPartsUSA

iTrader: (3)

Not sure if you have looked into this but we can revalve Koni shocks and covert the front to a coilover and the shocks would be adjustable rebound wise. You would just need to retain the rear coilover components for custom race springs.

Cujo159

iTrader: (3)

Awesome. Glad to finally have that hard data for the suspension geometry.

I'm still trying to decide whether I should stick with the true coilover mods I have to move back to the OEM set up. True is easier to set up but I'm looking at about 2700 for the coilovers. Going back to OEM would require all those OEM parts as well as KW V2 or V3's.

Unfortunately I can't adjust my cusco sways. I'm trying to find a set of Hotchkis ones to put on full soft.