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How many threads on coilover to be safe?

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I have FINALLY finished just about everything for my coilover conversion in my 1978 280z with Stance coilovers. I also have TTT control arms. I am at the point of dialing-in the ride height. Stance gave me four 6" threaded sleeves. I had them welded right to the hubs in the front and 3" above the hubs in the back. I was hoping to maintain stock height or maybe 1" lower than stock.


Well after getting everything on and lowering the car, it looks like the front was lowered around 1" and the back was lowered around 2". I would like to crank the rear up another inch. The problem is, the threaded sleeve is currently only on by about 5 threads in both front/rear. I am afraid to crank it up in the back because I feel like the coilover will sheer off if I go any higher with so few threads holding. So my questions are...

  1. How many threads are "safe" when screwing the sleeve into the coilover?
  2. I have not done anything with alignment, track width, etc. Will any of these affect my ride height?
  3. What are my options for raising the car if I can't unthread the sleeves anymore? Can I use a top-plate spacer or something?




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Have a picture of the rear strut and lower adapter? If you welded them 3 inches up in the rear you should have at least the diameter of the cartridge threaded into the sleeve. I'd have to go look at mine again. I'd lower it til the fender gap is gone. But that's just me.


Didn't ask this before but why are you trying to stay stock ride height?

Edited by JavelinZ
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Sorry, let me clarify.


The front struts were cut 1" above the hub. The adapters were welded at the hub. 1" of strut was was left inside of the adapter sleeve.

The rear is similar, except it was cut 4" above the hub, and adapters welded 3" above it (so 1" again was left inside of the adapter sleeve).


The adapters look like this by themselves:




In this pic, the red arrow points to the collars that adjust spring height. The blue arrow points to the collar that adjusts how long the entire tube is. I can screw the top section (part with shock & spring) all day without adjusting the length of the spring.




I want to stay at stock height or 1" below because I don't really like the look of extremely lowered Z's and also because I don't want to scrape everywhere I go. This is gonna be tracked maybe once or twice a year so I don't need extreme performance.

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The top two locking nuts make up the lower spring perch.  They generally they shouldn't be adjusted other to assure that the spring is snug between the upper and lower perch.  You normally don't want to "pre-load" the spring.  (raising the lower perch otherwise will compress the spring = pre-load - it does not lengthen the strut assembly)  The exception to this is if you had your car corner balanced - then the Tech would adjust the pre-load as necessary.


The short answer to your original questions:

1. No, 5 threads is are not enough.  Rule of Thumb is that the strut cartridge should be screwed in approximately the diameter of the threaded adapter - so, about 2" as a minimum.

2. No, Alignment and track width will not affect ride height in a significant way.

3. Ummmm...  I think the best way would be to go back to your welder/fabricator and have him add back in at least a couple of inches on the stock strut tubes.  (nice welds BTW...)


About the minumum safe distance for the strut cartridge in the adapter:  Give the super nice guys at Stance USA tech support a call.  Their struts are all steel, they may not need a 2" insertion, but those guys will give you the facts. 847-290-1568


After you talk to Stance USA, screw the cartridges into the adapters the amount they say.  Figure out how much you need to lift the rears and have your welder add at least that much back into the rear stock tubes (keep in mind that you still have some drop in those adapters).  Hopefully you can live with the fronts - that will be more difficult to change at this point. 




A few things (you're already past most of this, but it's mostly for others installing their own):


This is why I was trying to stress "doing the math" first.  Especially since you wanted to stay near stock height.  Not one other person that I know of has installed our kit to maintain stock ride height.  So, asking them how they did theirs would not help you.  


To figure the math properly, you would need to measure the loaded length (springs compressed normally) of your stock struts.  From the top of the isolator down to the hub.  Wheels on the ground, everything in the way...


Compare the stock strut length with the assembled length of your Stance USA strut cartridge (strut cartridge threaded into threaded adapter 2", lower spring perch unchanged (or adjusted so the spring is just snug), pillow ball in place, aluminum lower camber plate attached to pillow ball if using our camber plates)  Measure the length of this assembly from the bottom of the adapter to the top of the camber plate.


- Your new springs will compress slightly but not nearly as much as the stock springs did - probably an inch or less.

- Also keep in mind that with 2" threaded into a 6" adapter, you still have another 2"-3" to lower.

- leaving an inch of the stock strut tube in the adapter is really not necessary.  1/4" is sufficient when welding to the hub. 1/2" is more than enough when welding up on the tube.


With those measurements you can compute the proper position of the threaded adapters.

Example: (totally pulling these numbers out of the air)

The stock length of the rear strut is 25" from the hub to the top of the isolator with the car sitting normally on the ground.

The assembled length of the Stance USA / Sakura Garage coilover (as described above) is 21".

Let's suppose that the Stance spring will compress 1" with the weight of the car.  21" - 1" = 20" (adjusted length)

25" (stock strut length) - 20" (adjusted Stance length) = 5" height difference.  

The threaded adapter would need to be welded up 5" on the tube for stock ride height.  

If you plan on keeping a 1 1/2" lower stance on the car, the adapter would need to be approx 3 1/2" up the tube.  (5"-1 1/2")

Keep in mind the adjustment (lowering) you still have in the threaded adapter...

Edited by cgsheen
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Welp, after some discussion it sounds like I accidentally included the top pillow mount of the stock strut in my measurements. When converting to camber plates, you don't use that pillow mount anymore. That thing is a good 2-3" thick, which explains why my car is so much lower than I expected. DOH! lol

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To echo cgsheen

1. Usually you want 1.5 x diameter for thread engagement as a general rule, for something as large a bore as this you probably can do 1 x diameter.

2. Track width and alignment won't necessarily affect your ride height unless you lengthen the LCA a significant amount to lower the angle of the shock in effect lowering the car. You could in theory do the same with enough camber, but not enough significantly with most coilovers to adjust ride height unless you are on a very aggressive wheel.

3. For the rear you can have it cut and a spacer welded in. For the fronts you are kind of in an odd spot, if you were positive you were never going to go that low you could have it cut near the bottom and add material as well, but that will be in the threaded portion so you wouldn't have your full adjustment. You could do a top hot spacer, but then your pivot point for the shock changes. Not sure how that would affect geometry, but you would be shortening one leg of the triangle. Easiest would be to up the tire size if it is concerning. I think a 2 inch drop looks pretty good on a Z.



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