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My 89 Z31 suspension build

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  • My 89 Z31 suspension build

    Ok here's my first post, nice forum by the way. I've been reading all I can on this forum to get more familiar with the koni's I want. Here's what info I've gathered so far for the rear and was looking for some advice, this is a cut & paste from a pm I sent a fellow Z31 autocrosser.

    "Ok after talking directly to Koni this is what I've found out. Take a look at my chart

    KONI SHOCKS____8042-1026SPORT(DBL.ADJ.)____8042-1134SPORT(DBL.ADJ.)
    MAKE___________FORD MUSTANG 87-93________FORD MUSTANG 94-04
    STROKE MAX_____519MM/20.43IN_____________501MM/19.72IN
    STROKE MIN______315MM/12.4IN______________372MM/14.64IN
    STROKE LENGTH___204MM/8.03IN______________129MM/5.07IN
    ROD SIZE_________12MM/.47IN________________12MM/.47IN

    MAKE_________NISSAN 300ZX NA 1988
    STROKE MAX_____609.3MM/23.99IN
    STROKE MIN______392.5MM/15.45IN
    STROKE LENGTH___216.8MM/8.54IN
    ROD SIZE_________12.5MM/.492IN

    Based on these number I think the 8042-1026sport would be a good choice for my car since the stroke is within .50" of the stock shock. It will allow for a 3.56" drop in total height of the shock, remember this is the height of the shock not the car. The height of the car depends of the spring rate and how high the coil is adjusted when loaded. This just means to me that when I jack the car up I'll have less distance to go before the wheels lift off the ground. Now in the case of the 8042-1134SPORT I think the stroke is just too short. Causing the inside rear wheel to lift when in a hard turn when the front outside wheel gets loaded, correct me if I'm wrong. Also Koni already makes the coil sleeve, top and bottom hats to make these a true coil over shock. The koni rep did tell me that these shocks would hold the 500-700lb springs I asked about, so no re-valving need for that range at least." end of pm

    For the fronts I was planning on using some koni 8611-xxxx inserts. Because my car has front McPherson struts I was told that I had to remove the insert in order to adjust the compression adjuster. Being the mechanical design eng. that I am I decided to try a make a right angle worm or bevel gear that would attach to the bottom of the 8611 insert and act as a way to adjust the compression adjuster without removing the insert from the strut. I would drill a hole at the lower part of the strut giving me access with a screw driver to the right angle driver which would turn the compression adjuster. I like the front height of my car currently with it's MSA springs and Tokico hp inserts but the rear springs have sagged over time to the point that I hit the stock rubber bump stops on my MSA spring/tokico hp shocks in the rear. My idea in the front is to get a 8611 insert close enough to the stock insert in stroke/height but still allow for the adjuster contraption to fit without having to section the strut.

    Initially I was going to swap the front strut with some s14 spindles and 5-bolt hubs and use some ots s13/14 shocks (stance) front and rear. That is until I found more info on the koni 8611 series. Any insight would be greatly appreciated.



  • #2
    3.5" shorter is a pretty considerable amount.
    Between rides...unless you count a WD21...


    • #3
      After thinking about this for a while I think that 3.5" would be a problem for a daily driver. I think I'll just let GC build the system for me instead of me using off the shelf koni mustang shocks. Which I'm sure that's what they'll use but they may extend the shaft to fit my Z. I'll find out for sure since I need to get this done soon. Getting tired of going through new tires because of my worn out suspension making the camber geometry way out of spec.


      • #4
        That Z shock is pretty close to the same length as a S14 rear though.
        Between rides...unless you count a WD21...


        • #5
          You mentioned a shock and then a strut. If you have a strut, you should be careful trying to use a shock as a replacement.


          • #6
            The front on a Z is a strut and the rear is a shock. (similar to a 240SX)
            Between rides...unless you count a WD21...


            • #7
              Yes the front is a strut with an insert and the rear is a standard shock, eyelet on the bottom with threaded rod on top. Seeing how it is a daily driver and I only plan on just starting out in road racing do you think that I should just go with the single adj. instead just to save some money? An s13 front/rear shocks has been successfully installed in a Z31 suspension. The only issue being is the front where the strut needed to be cut very low then welded to the lower portion of the front s13 shock bracket. Pretty crude but it worked. The other option is using an s13-14 front/rear shock (the typical full threaded variety like stance since the s14 rears are too long in stock form, s13 rear length are fine) and use the s14 front spindle with 5-bolt hub and the s14 lower ball joint. A spacer ring would need to be welded in the lower control arm in order to fit the s14 ball joint since the z31 one is bigger. The guy I talked to about this setup is a road racer out of california but he is using some s14 kei office xt shocks I believe on his setup.


              • #8
                If you're not looking to break the bank, I'd just try to do some S13 style rear Koni yellows in the rear if you say they'll work.

                Someone mentioned some year of an Eclipse rear Koni yellow fitting an S13 and being externally adjustable. Might want to look into that.

                Not sure why you couldn't adjust the 8611 compression adjuster while everything is on the car, I can do it just fine on my S13 with room to spare. 49 cent Harbor Freight stubby screwdriver is my adjuster tool of choice.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!

                DefSport Koni Sleeve and Spring Perch Buy!!!


                • #9
                  Def, I think the Z31 front lower mount is Corolla style. Meaning there's no way to get to the bottom of the insert without having a hole through the ball joint/lca/spindle/etc.

                  So what's the deal with switching to S14/S13 stuff? Then you could run the 8611 and be able to adjust everything on the car.


                  • #10
                    Originally posted by Wiisass View Post
                    Def, I think the Z31 front lower mount is Corolla style. Meaning there's no way to get to the bottom of the insert without having a hole through the ball joint/lca/spindle/etc.

                    So what's the deal with switching to S14/S13 stuff? Then you could run the 8611 and be able to adjust everything on the car.
                    Wiiass yes your right it's like a Corolla style in the front just as you described. The deal with the s13/14 stuff you can find here: Z31 to S14 front suspension download the pdf this guy made.

                    I've been in contact with the guy that did this and he is happy with his results. It's still not a complete bolt on affair but close minus the ball joint difference. He has tracked his car since that swap and was still happy with the results. Here's a video of him and his car on the road: zmech's Z31T with s14 front spindle swap and coil overs all around

                    I do already have the s14 front spindles, I just need to buy 5-bolt hubs if I follow this route. This was my initial intentions to do with my car and I still may go that route.