Suspension: Hooking up the Z31

[Jaysun]

My Z31 is nearly 20 years old, it has 130 thousand miles on it, it floats over bumps, rolls in the corners, and sags in the back...what Z doesn't? So a suspension upgrade is in the works and I'm just letting you know about it (b/c I'm bound to have some questions along the way)! Here is what I'm looking to for:
---Improved handling, feel, and response
---Stiffer ride but not too stiff
---Considerably less body roll
---Elimination of sag and excessive camber in the rear
---Adjustability: dampening, camber, toe, etc.
---Quality stuff that will last a long time
**Just to let you know, this is a 1987 Turbo Z31 manual 2-seater
**Also, since it seems to be a dividing line in the Z31 community, let me state this...I *do*want to lower my car around 1” (+?)





With that being said, I'm attacking the car's handling deficiencies head on with one fell swoop. This week my car was lifted in the air and it won't come back down till these problems are solved. You can see that I have already removed all of the suspension. Now I've been collecting the necessary parts and they are all here (except one that I'll tell you about in a sec)! Here is what I got:
---Polyurethane bushings, the full kit from Motorsports Auto plus the rear subframe bushings
---The off-center bolts from a junkyard Z for the ubiquitous camber adjustment mod on the rear control arm
---Some 1/4" iron bar stock to make the guides for said off-center bolts as well as a round file (a bastard if you will)
**This isn't really suspension...but I have Z32 4-piston aluminum calipers for the front, the 1/2" washers needed to center them over the rotor, stainless steel brake lines (front only) from PDM Racing, and front pads that will be going in too
**Also, at this point I am not planning to add any sway bars or strut tower bars...yet...just to let you know.

Now, you probably noticed one key ingredient missing in my suspension upgrade...springs and dampers. This is that "one" item I was referring to. The shocks and springs have not come in yet b/c I have not ordered them yet. I'm hung up on this part.

[MrwassmanNA2T]

wow, you have a nice shop to work in

[Steve88t]

I know this thread got a bunch of conflicting responses last time so I'll make my respsonse simple:

If you have looked at the commercially available springs and dampers then you know there is only one way to drop the car any and keep reasonable performance; the ST springs. Yes I know the SS springs are close, but they are more expensive with similar specs.

If you dont want to go that route, you'll have to do some fabricating. It is well worth it if you have what it takes to do so.

If you have the money, a good set of adjustable dampers with 300lb+ springs is still very comfortable. Not harsh at all. I know Jason is using WAY stiffer than that, but he has much nicer dampers than my Illuminas.

Also the ground control upper mounts would be the best way to top it off. If not, you can slot the towers to get the same result with a stock mount. But you have to be EXTREMELY carefull you get it right.

Obvious stuff is replace everything rubber with poly. So much cheaper and better overall.

That's a pretty car and a pretty shop you have there.

[Lance]

If you want a ton of options, look at coilovers for the s13.

http://z31.com/mods/coilover.shtml

It does take some extra work but it looks like you can handle it.

[Jaysun]

Yeah, this thread wasn't really going anywhere before the server crash...I'm going to take the discussion a different route this time...sorry for the parts that are a re-post...

The easiest thing to do would be to order stiffer springs, the ones by Suspension Techniques, and the 5-way adjustable Tokico Illuminas and call it a day. I almost picked up the phone and did this…but this just doesn't sit right with me. The Suspension Techniques drop the car 1” (what I want) but they have a spring rate of 200/226 [lbs/in] in the front/rear (not enough). See, my car is the 87 Turbo, so it already has 196/188 rate springs. Any other lowering spring would be a downgrade. All the Suspension Techniques springs would do is lower the car…but they would (*assumption*) behave basically the same as my current springs (minus the effects of the poly bushings and adjustable dampers).

So, I'm highly considering a coilover setup. I have the tools, the ability, the desire, and the money (time, I don't have *too* much of that). But that doesn’t quite sit right sit with me either… Here’s the current state of the art in Z31 coilovers:

FRONT) You weld the 240SX S13 coilover to the Z31’s strut tube…ok, that’s fine, I can do that…I don’t really want to cut my strut tubes and weld but I can if that’s the only way to do it. Now for the camber plates so that I can get the adjustability I wanted you have to slot the Z31’s shock tower bolt holes to fit the S13’s slightly different bolt pattern…well, I *hate* putting holes in my car’s body, but ok, I can do that..
REAR) So I take the spring out from where it sits and unbolt my damper then bolt in the S13’s coilover to co-locate everything where just the damper used to go…ok, I can do that…but should I do that?

When Jason84NA2T installed his rear coilovers (http://www.redz31.com/pages/coilovers.html) he confronted the issue about putting all the car’s weight to the shock towers...some said this was not a good place for all that weight, he disagreed and explained why. I tend to agree that the towers can handle the load but my question is whether the lower mounting points can handle it. Look and you will see that your stock Z31 damper mounts to the rear trailing arm via a bolt-on hanger extending rearward from the hub area. This hanger is held in place with two bolts, one anchoring it to the trailing arm and one acting as a pivot. So being an engineer I like safety factors and controlled failures. The thing that bothers me about this setup is that it creates a single point of failure and one with negative stability at that…negative stability in that the hanger mounts to the bottom of the trailing arm and the weight of the car is always trying to push it off. See, I would rather the coilover mount to the top of the trailing arm itself so that its load is transmitted by pushing down directly on the trailing arm.

But these issues aren’t so bad. And the few that have installed coilovers report great results and, as far as I’ve heard, no problems (thanks a lot for pioneering this BTW!). I mean, once you get the things in there then you have unlimited options! Ride height, damping, spring rates, camber, toe…all there for you to play with and dial in. That’s what I like!

[Steve88t]

You can do more than cut the strut tube for the front. most of us modified the stock tube to accomodate a spring perch. It works just fine and is just as adjustable. BUT you are limited by the dampers that will fit in the tube.

As for the rear, I have never seen that mount fail and am not concerned it would with the rates most of us will ever use back there. If you dont like the piece, make a new one. It would not be hard to fabricate a new one.

[G-E]

Look and you will see that your stock Z31 damper mounts to the rear trailing arm via a bolt-on hanger extending rearward from the hub area. This hanger is held in place with two bolts, one anchoring it to the trailing arm and one acting as a pivot. So being an engineer I like safety factors and controlled failures.
that "thing" failed on a z31 before.... rookie in his slightly rally abused car I think, I'm sure failure isn't sudden, cracks develop and deformation and eventually crack/rip/pop

The Suspension Techniques drop the car 1” (what I want) but they have a spring rate of 200/226 [lbs/in] in the front/rear (not enough). See, my car is the 87 Turbo, so it already has 196/188 rate springs. Any other lowering spring would be a downgrade.

as answered last time, dan-tss's springs in the rear will drop the car a touch, not 1" but the TSS spring rate is another 20-40% over ST spring's rates

those springs with either tokico illuminas or koni rallisports, poly bushings, (insert plug) my poly diff mount.... and you should be rock hard like a pornstar on pills

[Russ84na]

I got my coilover set up from Ground Control. The front was easy only cutting and welding was to cut off the old spring perch and weld on the new one. I used Koni sports 8641-1060 with 600.250.500 springs.
The camber plates bolted right on. Had to grind on side of the adjustment washers to get the camber I wanted.

The rear was really easy except I didn't like the method used to hold in the springs. You can see what I did on http://www.redz31.com/pages/coilovers.html. The PVC pipe allows me to change the springs by just jacking up the car. Otherwise it can't fall out. For shocks again I used Koni's except the ones recommended by koni were only adjustable by removing the spring. So I used Koni sports 8041-1302. They are adjustable on top like the fronts and all you have to do is remove the rear speaker cover and maybe the speaker. Not sure as all that stuff is gone in my car. The springs in the rear are 800.250.700.

This car is set up for autoX and 500 lb front and 700 lb rear would not be very comfortable for the street.

However the springs are easy to change and available in all rates. Also the ride height can be lowered a bunch, mine is over 1" and you can cornor weight the car.

[WhiteZ31]

nice shop and an even nicer lookin turbo

[jjewell]

with the st springs and tokico illumina's you can pretty much go from a ride that is much stiffer than stock or a ride that will knock your kidneys into next week. i to have a 87 turbo with the st tokico setup with poly bushings and msa sway bars. i took the 87 and my 350z to an autocross event last year and the 87 was over a second faster than 350 all day long. the car handles great with this setup the only down fall is scraping on everything from small speed bumps to just about any driveway that has a slight incline.

[Jason84NA2T]

jjewell wrote: the only down fall is scraping on everything from small speed bumps to just about any driveway that has a slight incline.

Hmm, I still manage to not scrape mine most of the time and my car is lowered almost two inches.

Either way you look at it, when you compare the illumina/ST combo to stock it's a HUGE difference. I'm sure it will work nicely for you.

[Jaysun]

Just an update:

The suspension is pretty much ready to go back in...the subframe has been slotted, most of the old bushings have been removed, etc. For the rear camber mod, instead of using bar stock, I welded on 4 plates from a junkyard Z's toe adjustment.


Also, did I mess up here?! I was removing the bushings from the rear trailing arms and I pushed the inner sleeves and most of the rubber out. Then I hack sawed the outer sleeve to remove it (like you do for the poly subframe bushings)...then I stopped...looked at the new poly bushings again and saw that they about the same diameter as the inside of that outer sleeve. I was supposed to leave that outer sleeve in there, right?

[Jason84NA2T]

looks good.

Yes, you need to leave the outer sleeve in the control arm to use the prothane poly bushings.

[jjewell]

the tbo lip on the front doesn't help with scraping on stuff. the front sits really low . i even had a hard time getting the car straped down to the dyno without putting the car up on 2x8's.

[FreeLanceBum]

I welded on 4 plates from a junkyard Z's toe adjustment.

How hard is it to remove those? And how exactly did you go about doing it?
I was hoping to be able to do that, for when I tackle my camber issues.

That's a real nice looking turbo BTW, nice clean shop too.