Restoration of BringaTrailer 240z - HLS30-35883

[Captain Obvious]

11 hours ago, inline6 said:

I get sick when I look at these pictures, but here we go:  With this close up, they all look like garbage to me

The nut doesn't look great, but threads are still mostly there.  I have already chase this with a 12M X1.25 tap because I have one.  I am waiting on the die to arrive to chase the threads for the shaft.

What happened to the threads on your struts is called "galling", and it is an unfortunate occurrence when using hardware like you have there. Especially the Ny-Loc nylon insert anti-vibration style of nuts. The worst situation is stainless Ny-Loc nuts on a stainless shaft. Just don't do it.

Here's some discussion about such matters in this thread. On or about page 14:
https://www.classiczcars.com/forums/topic/61542-koni-sports-for-classic-zs/?page=14

Here's some links that talk about thread galling. Some of these even specifically call out stainless nyloc nuts:
https://www.boltdepot.com/fastener-information/Materials-and-Grades/Thread-galling.aspx
https://www.anzor.com.au/blog/what-is-stainless-galling
https://www.westfieldfasteners.co.uk/Ref_Thread_Galling.html

 

[inline6]

I read about the galling issue in that first link.  I also read Koni's response and decided that they wouldn't have supplied nuts that were not correct for the application.  FWIW, they say they are chrome plated steel and not stainless.  And, I was determined to be careful to go slowly and to not over torque them to avoid problems.  I blame the digital torque wrench for having an intermittent failure.  But, that doesn't help me now.

With about a 1/4 of the threads on the shaft machined off, one would think that a taller nut engaging more of the threads might be a good idea to help prevent damaging the threads when some amount of over torque occurs?   But yeah, once the threads get wrecked, there is a bunch of metal floating around between the nut and the shaft threads.  And evidently, it is certain that a stainless nut (if it is) exacerbates the problem of getting the nut off because of heat. 

Is the shaft stainless?  If so, why would Koni supply these nuts?  It is a mistake?

Edited December 5, 2023 by inline6

[emccallum]

Maybe call Koni and plead your case but I wouldn't expect much from them. Its done, replace and move on. Dont let it ruin the day, as the car looks amazing so far!

[Patcon]

I agree ^^^^

In your position I would buy a strut and move on. Chalk it up to "tuition"; the cost of learning

[inline6]

9 hours ago, emccallum said:

Maybe call Koni and plead your case but I wouldn't expect much from them. Its done, replace and move on. Dont let it ruin the day, as the car looks amazing so far!

 

1 hour ago, Patcon said:

I agree ^^^^

In your position I would buy a strut and move on. Chalk it up to "tuition"; the cost of learning

 Heard.  Die was supposed to be delivered yesterday.  Tracking from USPS still just shows "in transit".  Lame.

Trying to accept my fate.  With all the money I am spending on this car, another $190 isn't the end of the world, but the dollars aren't fully my issue either.  I hate the waste of an otherwise new and perfect strut insert.  😞

[Captain Obvious]

22 hours ago, inline6 said:

Is the shaft stainless?  If so, why would Koni supply these nuts?  It is a mistake?

Most of the strut shafts I've messed with are chrome plated carbon steel, not stainless. But I don't know for sure what Koni uses.

As for "Is it a mistake?".... I guess that kinda depends on who you ask. If you ask ME, the answer is "Yes, someone at Koni made a mistake." Why do I say that? Because this problem keeps happening over and over again with those parts. It's clear that something is wrong and it's not just you. 

But WHO at Koni made said mistake, or what KIND of mistake was made is up for debate. It's either a materials specification mistake or a documentation mistake. At bare minimum, there should be warnings in their documentation about this type of failure and how to handle the installation process to avoid the problem.

Maybe specify (or even supply) some lube. Maybe switch to different hardware. Something. But the fact that it just keeps on happening to other new purchasers is an indication that something is wrong. I think you should take it up with Koni and see if there is any relief available. There was a Koni guy around here at one time. @KONI Lee

[emccallum]

Not trying to pile on, but my experiences with both Koni and Bilstein over many years has been mixed. Their directions suck, hardware is usually universal and may or may not be needed or fit (mostly speaking of boots), and my last z was just too stiff for my liking with Bilstein and poly bushings. I went with KYB and stock bushings on my current build. 

Its obvious from the work you have done on this build that you know how to thread on a nut!

[inline6]

Appreciate the info and thanks for the support.  I don't want to say, but it is accurate to say... that for that one nut, I know I tightened it more than the 37 ft-lbs.  It just became obvious from my experience of torqueing fasteners, even though the digital torque wrench failed to indicate when I hit 37 ft-lbs.  It has an "auto off" feature after about a minute of time to save battery life, so maybe it turned itself off before I used it on that nut.  However, I still believe I was being exceedingly careful and believe I checked the display to confirm the correct setting just before attempting to torque that nut. 

As far as the directions go, I definitely did not like them.   There were hardly any words... an over reliance on pictures.  Saves on translation, but doesn't convey info precisely either.  I already mentioned that I used coolant in the strut tubes originally because of the snowflake symbol.   

So, now take a look at this and tell me what you would torque the nut that is supplied with the struts to.  I will give you a start with the threads being 12M X 1.25 and a picture of the supplied nut:

 

Think everyone gets it?

Edited December 7, 2023 by inline6

[Captain Obvious]

At quick glance, I would interpret the torque spec for that nut to be 59 ft-lbs

And no... I don't think that nut could handle that.

[emccallum]

I would have gone with 37 :). 

[dutchzcarguy]

I would have gone for 80Nm.. (think.. For example the wheelnuts are about the same and they are on 100-110 Nm.. ) So 59 Ft-Lbs..  

[inline6]

Yeah, it is not obvious which is the right torque value.  

I decided to try to save the strut insert and spent a couple of hours giving careful attention to the threads.  I used this tool which is for repairing threads:

 

Using a lot of patience, I kept at it until the new coupler nut would thread on without difficulty.  Here's how it looked after all that effort - these pictures capture how it looks all the way around the circumference.  While not "great", the threads look better than before. 

    

 

Also, note that the 4 to 5 threads just above the spacer (a bit more than a 1/4") were not mangled because the thickness of the isolator stacked on the spacer protected them.  As I examined the situation, I determined that I could "alter" things a little bit, so I could utilize those threads.  Basically, by shortening the spacer, the isolator can slide down further on the shaft and expose those threads to the fastener.  I started by putting tape on the shaft to mark the area that I needed to grind to fit the "D" in the upper strut mount isolator.  And, I taped off the adjustment mechanism to keep metal dust from getting into it.

      

 

After using a belt sander to grind the "flat" in the shaft a little lower, I had to remove the same length of material from the bottom of the spacer.  I don't have a lathe, so I had to be very careful with grinding.   After removing some length, I very, very carefully used the side (which I have never used) of my 8" bench grinder wheel and kept measuring with vernier calipers until the cut side was square with the non-cut side.  Then, I chamfered edges (middle pic).  The shortened spacer length matches the shaft again (third pic here):

      

 

Final pics, with the third pic here showing the coupler nut after shortening it also.  

    

 

I could have shortened the spacer and the nut a bit more to pick up another couple of good threads.  However, given that the original nut only engaged about 7 threads, and this one engages more than double that (though some are in very bad shape), I felt grabbing those last two was not necessary.

Today, I assembled the strut, put it on the car, and used that same torque wrench to set the nut to 37 ft lbs without any issue whatsoever.  I used a good bit of blue Locktight, which will keep the nut from backing off.  

I plan to check the torque on that nut repeatedly as I put the first 500 to 1000 miles on the car.  If it turns when retorqueing or feels odd at all, I will swap the insert for a new one.

 

Edited December 10, 2023 by inline6