DIY Coilover Rebuilding Q's

[spencyg]

So I just acquired a set of Tein NA coilovers from a member here and am planning on a complete disassembly and rebuild. I have scoured the web looking for some Tein-specific answers and have come up with very little. What I do know is this:

-Tein apparently does not support individuals who rebuild their own stuff (very lame)
-The Tein NA is discontinued (I knew this going into it) and they are only valuable to me if I can learn to service them myself. The rates that Tein charges to service shocks makes all but the $1500+ struts basically throw-away units.
-The NA shock is fully rebuildable
-The NA is a twin tube nitrogen charged design with 16 way adjustment

The units I have are in relatively good shape. 3 out of the 4 adjusters seem to be seized up though, so I need to get in there regardless to fix any issues I find. They aren't leaking anywhere, but I would plan on changing all o-rings during the process.

So the questions I have, but don't have answer to are the following:

-If there is any remaining nitrogen charge in the struts, how do I relieve pressure safely? There are no external valves which can be plainly seen.
-When rebuilt, I don't know where to recharge the nitrogen....the answer to question 1 would probably answer question 2 as well.

Since they are twin tube, I could easily modify the external tubes when they are disassembled to allow the use of a schrader valve for future discharge/recharge. For now though, I really don't want to pop the caps until I know how to bleed the pressure. Without that assurance, each shock is a potential mini-bomb waiting to shoot my eyes full of shock oil.

I'm sure most of the folks around here probably don't dabble in this level of tuning, but I have messed around with dampers before and enjoy it. The desire to rebuild is as much about the enjoyment about knowing every single aspect of my car as much as it is not wanting to shell over big bucks to rebuild discontinued struts.

Any help would be very very welcome.

Thanks

SG in NE

 

[supraguru05]

I thought tein was around 100 a shock to just rebuild, + 50 for a revalve. That doesn't seem to bad in my opinion. As far as any guidance on rebuilding I cant really provide anything

 

[spencyg]

Since there is such a delay in posting a message in this part of the forums and it actually appearing, I have found some other things out, and actually pulled apart one of the Tein NA coilovers. Basically the NA damper (along with presumably all of their other twin tube offerings) is somewhat of an emulsion shock with the Nitrogen gas being allowed to mix with the oil. There is no nitrogen bag, and certainly no floating piston (since that would make it a monotube, obviously). 3 out of the 4 struts I have still seem to be holding their factory charge which is actually pretty incredible considering how old these are. The 4th strut (when the spring was removed) had obviously failed in a pretty serious way. I took this opportunity to disassemble the unit without concern for relieving the gas pressure. What I discovered is that the inner workings are pretty standard faire. Inner and outer tubes, a valved piston with a simple needle valve bypass for the "16 way adjustment", base valve which some spring loaded shims, and a head bearing. The failure of this particular shock appears to be due to somebody at some point in time trying to remove the shock with an impact wrench or something, spinning the nut off which retains the piston, and the whole works fell apart inside the inner tube. No damage was done except for a strange one way check valve of sorts built into the upper bearing. I'm still trying to figure out the true purpose behind this valve....especially since Tein WILL NOT sell parts to the public. I have contacted them multiple times explaining my situation and the fact that I do my own work and would rather stab myself in the eye than send them my shock. Needless to say my opinion of Tein's policy on this is generally disgust, but they basically said that if I want a shock which parts are available over the counter, I should probably buy something else. Great attitude Tein...way to alienate those who actually want to be involved with the inner workings of their cars. Awesome.

So since I have no choice and I need this component replaced, my plan is to disassemble all of the struts and throw any bad parts into a single assembly. That assembly will be shipped to Tein where they will do their thing for $150-$200 (including necessary parts). I'll then take apart what they send me and distribute the new parts to the appropriate assemblies.

This whole thing is so silly.

While I have these units disassembled, I'm going to sandblast the cases and install ports at the base of each tube which will initially be used for schrader valves. Eventually I'll remove the schraders and instead install remote reservoirs. This will convert the struts into somewhat of a hybrid design where the pressure for keeping the oil from boiling at higher temperatures will come from that remote floating piston reservoir instead of the secondary tube. This will give me considerably more oil volume and will eliminate any mixing of gas and oil. It will also make servicing all the easier.

I want these struts to be very customizable, and the Tein really does make a nice product with which to start this process....if it wasn't for their pathetic service support I would be touting their greatness...unfortunately I won't be doing that. Anybody who wants the ability and support to work on their own stuff should stay as far away from Tein as possible.

I'll be posting progress on this as it occurs.

SG in NE

 

[White Zombie]

Have you tried talking to other manufacturers of coil overs ? Do they also not sell individual parts , or is this just a Tien thing ?

Where did you get the experience of tinkering with shocks ? Did you do that on your own or learn it somewhere else ? Something I've been interested in too , but haven't had the need ( since my shocks ARent blow yet )
Otherwise good info so far ...

 

[Poodles]

There's dozens of good reasons why they don't sell parts to people, and they're not the only company that does so...

 

[spencyg]

Well Fox, Bilstein, King, and a slew of others obviously have it all wrong then.

I think the only reason is because they consider the servicing of their products to be a valuable source of revenue.

After looking again at the "check valve", I realized it isn't that at all...its the top of stroke bumper. I can recreate this with some Urethane easily enough, so these shocks aren't going back to Tein. Forget them.

 

[Poodles]

Yep, you hit the nail on the head. Plus you don't see Tein on "real" racing vehicles like you do Bilstein, so it's really a tuner car market where there a LOTS of copycats (you see where I'm going with this...)

 

[spencyg]

Tein actually does have a fairly respectable racing history....I think the biggest thing is that they are a foreign company without AS MUCH of a racing history as the others. Plus, the little bit of racing they have done has all been with pro teams. More "grassroots" representation would force them to act a bit more "civilized" since those of us who do are own work (for whatever reason) woudln't give a company like Tein a second glance.

Still looking like I'm going to just build a "bad core" strut to send to Tein. I found a couple more worn/broken items which can all be mixed/matched into a single unit for "replacement".

Also seriously considering converting these into reservoir style shocks. It goes against the original intent of a reservoir on a monotube, but will actually work well. The only purpose for the introgen charge in a twin tube is to keep the oil under pressure. Since Tein mixes the gas and oil, it compromises this a bit since the oil can "airate". If the primary tube was completely full of oil, and the pressure for the tube came from a remote source (i.e. the reservoir), than the additional oil capacity will keep everything cooler, AND the remote reservoir will totally seperate all oil and air/nitrogen mixing possibilities. I have run this by a few professionals and they all think it will work great.

I'll be sure to update with some pics as progress occurs.

SG in NE