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Discussion Starter · #1 · (Edited)
Getting ready to install my KWs and was ignorantly expecting them to work with my PDV rear spherical mounts. Realized that the OEM 4c shocks use a M12x1.75 thread on the top of the shock while KW uses a M12x1.5 thread. PDV top nut will not work and a new one needs to be made.
Mount Bearing Nuts.jpg
The other issue is that the KW shaft diameter is less than the 4c shaft diameter which means that the spherical bearing will not rest on the shock shaft. Need something on the shock for the spherical bearing to brace.
KW Shaft and Spherical Bearing.jpg
Spherical Bearing I.D..jpg
KW Shaft O.D..jpg


Decided to make my new top nut so that it could also be used on the bottom. The shock will be securely braced to spherical bearing from top and bottom with two of the same shoulder nuts.
Fusion 360 Screenshot.jpg
 

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Discussion Starter · #2 · (Edited)
The specs of the PDV top nut had to be adjusted. Hex head height was about 4.5mm on the PDV nut which had to be brought down to 3mm.
PDV Top Nut Hex Head Height.jpg

The threaded shaft on the KW is pretty short compared to 4c which is why I brought hex head height down to 3mm.
KW Shaft Total Length.jpg

Spherical bearing height is 19mm.
Spherical Bearing Height.jpg

There are two nuts, 3mm + 3mm + 19mm = 25mm. Total exposed shaft length is 29.5mm which leaves about 4.5mm for a wrench to counterhold the KW shaft as you tighten the top nut when installing. VERY CLOSE!
 

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Discussion Starter · #3 · (Edited)
Barrel length of my top nut will be slightly longer than PDV top nut at 7mm bringing total height of my top nut to 10mm. Barrels will extend a little less than half way through the spherical bearing. Total height was 19mm, each barrel is 7mm so there will be 5mm of clearance in the middle.
PDV Top Nut Barrel Height.jpg

Barrel O.D. will be the same at 18.96mm.
PDV Top Nut Barrel O.D..jpg

Some other measurements if you're interested:
PDV Top Nut Hex Head Width.jpg

KW Threaded Shaft Length.jpg



Anyone have any objections to this idea before I get them fabbed up? Would like to hear if anyone else has already gone down this road before.

If this fails or doesn't work out as intended, I have some other ideas, they would just be more work for me or would require a more complex top nut. This seemed like the easiest, simplest approach.

I currently have the job posted on 100kGarages and have two fabbers who have contacted me. Waiting to hear back from both of them.

If pics don't work I can reupload.
 

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is there a reason you don't just specify a different spherical bearing? Or could you not find one that has the correct dimensions?
 

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Discussion Starter · #5 · (Edited)
is there a reason you don't just specify a different spherical bearing? Or could you not find one that has the correct dimensions?
Yeah I looked and looked and I couldn't find a stainless one that had a smaller I.D. while maintaining the same O.D. to be pressed into the existing PDV housing.

If there is one, then that would save me a little work and I could beef up the top nut I'm making, or eliminate the need for one if the I.D. was exactly the same as the shaft.
Sent from my ONEPLUS A6013 using Tapatalk
 

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Discussion Starter · #6 ·
Just put in the order for four of deez nuts! I'll have them in 2-3 weeks, we'll see if they work out.
 

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Discussion Starter · #7 ·
Just received the shoulder nuts a couple days ago. Installed them and it looks like everything is going to work out as planned! My only concern is the long term strength of the bottom nut if the car went over a lot of jarring bumps. We'll see how it goes.

IMG_20190527_143050.jpg

IMG_20190527_143054.jpg

IMG_20190527_142902.jpg

I had the work done by Matt over at Fuqua Precision Machining. Glad to have found someone interested in doing small batch fabrication without charging a ton like emachineshop or any of those companies.

Started measuring and thinking about the spring seat adapters for 2.5" springs in the back and realized it's going to be a little trickier than I thought. Going to have to make a real world prototype and then make a 3D drawing based on that so I can get them made from billet. One day...
 

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Discussion Starter · #8 ·
Update:
I finally got my car back together after almost 6 months of downtime and these custom nuts seem to be doing the job just fine. I have only driven maybe 100 miles so far but I've pushed the suspension pretty hard a couple times and nothing broke yet *knock on wood. Also these KWs along with all the other stuff I did are pretty awesome, car corners so flat it's ridiculous compared to 4C with stock springs. I like the ride better too.
 

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2005 S60 T5 M66 with 4c
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what difference did you notice between the stock rear shock mounts and the pdv spherical ones? Also any specific differences when switching from 4C to the KWs? I never push my car that much as it serves as a family hauler now but rear end stability has always been pretty poor. I have a set of KWs in the garage waiting to go on so the differences between your R and my T5 should be minimal-ish.

What material are the flange nuts CNC'd from (I may have missed it). I'm guessing 304SS, which should work fine. You'll have a very hard time/impossible time finding bearings with the same OD and smaller ID, so this seems like a good solution. Was the flange press fit into the spherical bearing at all? or a loose slip fit?
 

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Discussion Starter · #10 ·
I don't remember noticing much of a difference when I installed the spherical mounts when I had 4C. They seem to clunk a little bit. In a controlled situation like on a track, I'm sure they have benefits but on the street you could probably skip them. I vaguely remember thinking they were helping a lot with sidehop in the rear but idk. With the setup I have now, it's totally gone and feels great.

I have the KWs dialed in to about 9 clicks from full hard right now and I also should mention I have 2.5" eibach springs (don't remember spring rate) in front not the kw springs and I also have delrin subframe bushings and powerflex race bushings all over mostly in the rear.
With all of this, the car is way more responsive to steering input and it corners extremely flat. With 4c shocks/springs, I felt like I had reached the limits of how the car could corner and was looking for more. The aforementioned has made it so I have a whole new world to explore as I can adjust the shocks manually and experiment with different spring rates. I would definitely not go back. When I take a corner at a speed that would've given me uncomfortable body roll with 4C along with some understeer, it just feels flat and really good. Ultimate goal is to make 2.5" springs work in the back so I can try to tune out as much understeer as possible but we will see.

As for comfort, I like KWs better. My 4C was working and the ride wasn't the best. I feel like with everything I've done I am trading a small amount of NVH for A LOT more performance so that's a trade I'm willing to make. I'm sure you could dial in the shocks a little softer and get a ride that is more comfortable and performs better than 4C. I'll play around with it today.



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Sorry to resurrect this but a current customer pointed it out to me and I feel its worth commenting on. Also, due to my poorly documented instructions I see a lot of comments about my mounts making noise or not being designed to mount correctly. I'll pull out a few high level topics and address them in the order I see them.

For a bit of history, I opened up my first group buy to BC and KW shock owners knowing there was some risk they wouldn't fit. The assumption was the shock companies would match the OE shaft tennon thread size and length. I am a professional damper designer, this is the typical approach knowing aftermarket mount and shock suppliers are looking fit as many vehicles as possible. Turns out I was wrong and refunded every BC and KW owner after taking a look at those shock designs and determining there wasn't a cost effective simple solution I liked. To be fair, I have more accurate KW shaft measurements in this thread then I was able to get from customers back in 2016 and I wasn't about to buy a $2k set of shocks to get some measurements. Maybe there is a path forward.

  1. Shaft tennon threads don't match.
    1. BC, KW, and OEM thread lengths and thread pitches are different. This alone is a perfectly manageable pain in the butt.
    2. KW's thread is very short. This is a bigger problem.
  2. The shaft diameters don't match.
    1. This is a bigger problem. As Tristan noted, the KW shaft doesn't even register on the spherical bearing because the diameter is smaller than OEM. Smaller shafts are great for shock performance but that doesn't work with my chosen bearing.
    2. The bearing choice was based on two things, misalignment angle and load capacity. Most standard spherical bearings don't have the available rotation angle to account for the P2 suspension motion which would lock up the suspension and bend the rod. Also, there are very few P2 track queens so my customer base is 98% hard street driven miles and we all SHOULD know spherical bearings are a wear item that will eventually make noise. I wanted to extend the life of the product as much as possible and choosing a spherical bearing that just barely fits the 12mm shaft thread will not be durable.
  3. Tristan's custom bottom nut. I can't tell if this was threaded or just slipped over the threads. I would not thread this and torque the lower nut against the upper nut to secure the shaft. This puts 100% of the jounce loads through the thread instead of into the shoulder on the shaft which is a bigger problem if your pretension does not exceed the jounce load. The pic posted looks like the bottom nut is not touching the shoulder, perhaps it is.
  4. Putting anything between the shoulder on the shaft and the spherical bearing reduces available jounce travel.
    1. First, I don't know how much internal clearance was built into the KW or BC dampers. When you lower the mounting position of the shaft relative to the OEM position you take up available jounce travel internally. At some point that means you'll have metal to metal contact internally and a shaft failure which is the most serious kind of damper failure you can have. Tristan added 3mm which is fine, I try to hit a minimum of 10mm when I'm pressed for space and who knows what these other companies do.
  5. What performance benefit is there? Can you really feel the difference?
    1. I posted a video at one point showing the OEM bushing flexing a lot as I drove around my neighborhood. It was enough to get me to commit to making the prototypes. All of that bushing deflection is the damper not doing its job for the sake of comfort. Pretty simple. It works and I did notice and improvement with the P2 "side hop" issue.
    2. My car had 4C shocks. KWs and BCs are undoubtedly stiffer and that would result in even more bushing deflection so the benefits for "racing" shocks are greater.
  6. Nut material
    1. I don't think 303SS is the appropriate material for this. Its soft and weak compared to 17-4PH Condition A and doesn't save much money. I think it galls more against steel threads as well.
    2. 122702
  7. Installation error.
    1. From the pics posted, Tristan installed the top mount correctly. This is not always the case and I find many that complain about clunking noise did not install correctly. Some have even installed the mount itself upside down. This is my fault in terms of documentation. I also think the torque required for the jam nut is not easy to achieve in the car without any flats to grab on the shaft. A hex on the end is certainly helpful but we can't get anywhere near the ideal torque with the tiny hex on the end of the tennon.
  8. The threaded post into the sheet metal in the trunk.
    1. This is something I've seen in other threads. The design isn't right or the clunking is because it doesn't bolt into the sheet metal. I call BS and I stand by that. There is nothing structural with regards to the hole in the trunk sheet metal. I considered cutting mine away to make installation easier, it does nothing because Volvo designed a massive cast aluminum housing to mount the spring and shock without taking up valuable trunk square footage. Zero forces go into the sheet metal above the top mount.
As for a good solution to sell with my name on it, I did try. This is my idea for BC shafts which would work for KW. Its very similar to Tristan's but has hex flats under the bearing and the adapter threads to the upper nut. I didn't like a number of things about it so I didn't pursue it. Perhaps there is a better way.
122703
 

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Discussion Starter · #12 ·
I am very happy to read your comments about this!
I am no engineer and looking back at this, I probably would not have done this the same way. However, they have about 15k of street miles on them and I have not had any issues. I would like to follow up on this though.

Tristan's custom bottom nut. I can't tell if this was threaded or just slipped over the threads. I would not thread this and torque the lower nut against the upper nut to secure the shaft. This puts 100% of the jounce loads through the thread instead of into the shoulder on the shaft which is a bigger problem if your pretension does not exceed the jounce load. The pic posted looks like the bottom nut is not touching the shoulder, perhaps it is.
Both the bottom and top nut are the same part, threaded. In retrospect, I guess the bottom nut really does not need to be but this was the easiest way for me to get this done at the time with this being the first custom part I ever designed and had machined in my life. The bottom nut is torqued downward against the shock shaft collar. Bearing rests against the nuts flange. The top nut is torqued down onto the other side of the bearing. The two nuts do not rest against each other at all inside the bore of the bearing.

Putting anything between the shoulder on the shaft and the spherical bearing reduces available jounce travel.
  1. First, I don't know how much internal clearance was built into the KW or BC dampers. When you lower the mounting position of the shaft relative to the OEM position you take up available jounce travel internally. At some point that means you'll have metal to metal contact internally and a shaft failure which is the most serious kind of damper failure you can have. Tristan added 3mm which is fine, I try to hit a minimum of 10mm when I'm pressed for space and who knows what these other companies do.
Definitely overlooked this but like you said I think the 3mm difference should be fine.

I don't think 303SS is the appropriate material for this. Its soft and weak compared to 17-4PH Condition A and doesn't save much money. I think it galls more against steel threads as well.
I wish I had done some more research about materials. I just knew it needed to be SS... that's it. It definitely is softer than I was expecting.


The main drawback with these is that they are kind of a pain to install and resintall because of that super short thread length on the KW shocks. I have not abused these yet but I am very happy with the results given the constraints, my limited knowledge and the cost to make these.
 
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Is there another bearing that could be used to suit the BC/KWs?
 

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Possibly but not without changing the design of the mount which I may do because the bearing I selected in 2016 is now 3x what I paid for them back then.
 
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