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Fun with Bilsteins

 
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Wiisass
Head suspension nerd


Joined: 09 Nov 2005
Posts: 131
Location: Philly

PostPosted: Fri Aug 10, 2007 4:38 pm    Post subject: Fun with Bilsteins Reply with quote

I've been trying to figure out the best way to have a good damper setup for my s13. And before anyone says, just buy some off the shelf coilover, everyone is happy with them, remember who you're talking to.

I wanted something that I could revalve myself. It would be nice if it was adjustable, but if I can revalve them easier, then it wouldn't really matter. After using the Bilstein Take Aparts on my brother's supra and having great success, I wanted to figure out a way to do that for the 240. Unfortunately, that's easier said than done. Because of the strut in the front and the giant mounting point in the back, it makes things a lot more complicated than they were on the supra. So I started looking into off the shelf dampers that I could mess around with. I found the part numbers for the s13 bilstein stuff and for some reason, they aren't available in North America at all. So I had to order them from the UK and since the dollar sucks, it costs a little more than I wanted to spend.

Anyway, the front bilstein struts are inserts for the stock strut tubes. But they're also inverted already. They use a 36mm piston, which although it doesn't have the parts availability of the 46mm piston, there's still enough out there that I should be able to get the curves that I want.



There are the 2 S13 Bilsteins. They're a little longer than I would like, but that can be accounted for in the strut tube. The yellow part is the part that goes into the strut tube and is bolted in at the bottom. It's a nice and simple design that with threaded strut tubes and threaded mounts could be used in a nice coilover setup.

So since I had to see what was inside, I ordered another front strut insert for a different car. I was able to find one with the same size piston, so hopefully there will be no differences besides some lengths and the valving.


Here's the test one all taken apart. Getting the yellow tube off was a pain in the ass. There's a cap on the top, that I can't tell if it's threaded or pressed or what onto the threads that go through the bottom of the strut tube. I spent a couple hours last night, try to get everything apart. And finally, I was able to at least get the yellow sleeve off, but that cap is still stuck on the top. I don't think i'm going to be able to wait much longer until I say fuck it and just cut it off.


Closer view of the shaft and piston. It's interesting that they use a longer shaft and a rebound bumpstop to get the shock to be the ride height for the application.


And here's the inside of the tube with the shock body guides.

For the rear, instead of paying for the overpriced S13 rear stuff from the UK, I just went with the available Z32 rear shocks. I have a set of Z32 uprights around here somewhere and would like to use them and figured it would be the easiest way. I am still looking for another shock that uses the same rear mount as the s13. And I think I know of one that will, but I'm not sure yet.


I don't have any pictures of the rears still together, but here it is apart.


And here's the Z32 shaft and piston assembly. This one also uses a rebound bumpstop to get the ride height out of the shock. So instead of using a shorter shaft, they just put a spacer in there to get it to sit lower. Oh well, I have a bunch of shafts that will work in these shocks. The parts for these shocks versus the take apart shocks are the same. So everything I can order from them, I can throw in there. I already know I need different rod guides and I need to add a schrader valve to the body, but besides the valving, there isn't much else that would need to change. I will probably change the shaft though and just use a custom upper mount. But it's nice because there are a lot of options.

So this setup looks like it could be promising. With a little extra work it should come together pretty easily. There's just a couple small things I'm hung up on at this point. And then I need to make adapters so I can throw the S13 shocks on a dyno and see where I'm at for the baseline. It should be fun, and hopefully I'll be able to have this setup all done for testing before the season is over.
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Dennis



Joined: 18 Sep 2007
Posts: 5

PostPosted: Tue Sep 18, 2007 11:32 pm    Post subject: Reply with quote

Tim,
Is the top out plate staked onto the piston rod or is if free to transfer the load onto the piston at full extension through the spacers riding on the shaft?

Nice site you got here!
Dennis Very Happy
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Wiisass
Head suspension nerd


Joined: 09 Nov 2005
Posts: 131
Location: Philly

PostPosted: Wed Sep 19, 2007 12:03 am    Post subject: Reply with quote

Dennis, it's all just sitting on there. The rubber bumper was a little hard to move at first but it was just sticking to the shaft. So at full extension, loads can be transferred to the piston rod.

I was actually surprised that this was Bilstein's method for shortening the stroke and overall length of the damper. I had always considered doing this if I needed some minor adjustments in shock length and had the travel to spare. But never followed through with it. I guess it's a very effective way of keeping costs down. Those spacers are a lot cheaper than different length shafts for every application.

Good to see you over here.

Tim
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Dennis



Joined: 18 Sep 2007
Posts: 5

PostPosted: Wed Sep 19, 2007 12:56 am    Post subject: Reply with quote

Tim,
The reason why I asked is because I saw something very similar to that inside a deCarbon shock for a late model Camaro. The green extension cushion was what caught my eye. However, in the deCarbon application, the top out plate was staked onto the piston rod itself. I know deCarbon did that to prevent the top out loads from tearing out the piston from the threads, besides other things. I am assuming GM required some sort of a max capacity within their OEM parts. I know we had to do this for some truck applications.

It is interesting to note that Bilstein chose to do this to cut costs. I would have thought that since monotubes lose lengths due to the gas chamber in comparison to twintubes, the collapsed length is critical. However it seems that it is not the case here. On an interesting note, that limiter design would have also cut down on the loads transmitted on the dynamic seal on a strut application, i.e. a Mustang perhaps? Wink

Thanks for having me here, Tim.
Hopefully I will have more things to contribute in the future.
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Ruff Ryder 6



Joined: 19 Mar 2008
Posts: 1

PostPosted: Wed Mar 19, 2008 9:39 am    Post subject: Reply with quote

I have been trying to follow this thread on both zilvia and on here and i thought of something that i would ask that you might be able to answer. I figure since the 240 uses an insert in the front, as does a 300zx (Z32), why not use the insert designed for the 300zx and use the strut housing from the 240? will this work that way. because like you mentioned, i too am going to use the Z32 aluminum uprights and plan on using the Z32 rears anyway, why not get the whole Z32 set and have them revalved for the 240? if i am way off base it's cool to tell me so but that is something i was just thinking about and thought i would ask someone with more experience in suspension work than me.
Thanks,
T.J.
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