The Strut thread - Koni / Illumina / Tokico / Carrera / Bilstein / Ground Control

[JMortensen]

No strut/shock ever made is fully liquid filled.

 

There has to be an air (or gas filled) void within the shock to deal with expansion of the oil as it goes from 50 degree temps in the fall to near 200 on a bumpy section of road.

 

If there were no air void, then shocks would be blowing up from the thousands of PSI that a non-compressible liquid would exert as it's volume grew when temps came up.

 

Turn a brand new shock over, pump it upside down, and you will hear this "air" gurgling through the valving along with the effect of losing damping.

Of course the damper isn't filled with oil. My point was that you aren't PURGING (getting rid of) air by cycling a shock. The gas can't LEAVE the shock, because most shocks are sealed and pressurized.

 

I got my Bilsteins revalved and when I got them first thing I did was flip them over and compress the shock on the ground upside down. Guess what? There are NO dead spots in the strut when you flip it and compress it.

[HowlerMonkey]

The damper is filled with oil and left with an air (or gas) void.

 

The valving intakes oil from the bottom of the shock.

 

If the shock is cycled upside down, the air void can be pumped into the valving and net you a shock that does not damp properly....until purged.

 

I purged the entire stock of koni, bilstein, boge, and controlle shocks we had in our warehouse at electrodyne in the mid 80s and have cut open enough "non serivicable, sealed" shocks as well as rebuilt OEM datsun shocks to know I am correct.

 

I also used the shock dyno as well as cut open a strut insert at VOB nissan to win this argument in 1994 and am 12 wins vs 0 losses in this argument since 1985.

[JMortensen]

The damper is filled with oil and left with an air (or gas) void.

 

The valving intakes oil from the bottom of the shock.

 

If the shock is cycled upside down, the air void can be pumped into the valving and net you a shock that does not damp properly....until purged.

 

I purged the entire stock of koni, bilstein, boge, and controlle shocks we had in our warehouse at electrodyne in the mid 80s and have cut open enough "non serivicable, sealed" shocks as well as rebuilt OEM datsun shocks to know I am correct.

 

I also used the shock dyno as well as cut open a strut insert at VOB nissan to win this argument in 1994 and am 12 wins vs 0 losses in this argument since 1985.

I guess the 13th time is the charm. I did this test twice. Once just to be sure I was right, and the second time to prove it. So the shock was compressed 3 times upright, then flipped and compressed 3 times upside down. Then I took the same shock and did the video. That shock was compressed 3 times upright, 3 times upside down, another 3 times upright, and another 3 times upside down. I've done the same with Tokico Illuminas many many times. I can't say that I've dealt with Boge, or Koni, or Controlle shocks. But for Illuminas and Bilsteins, you're wrong. I did put a nice dent in that railroad tie testing it out though.

 

http://www.youtube.com/watch?v=y21RpHo9e5c

 

EDIT--Video is available now.

[HowlerMonkey]

Congratulations, you have an exception in which your pickup ports for the valving is not at the extreme lower end of the shock.

 

Not every single shock made has it's ports in the same place relative to the fluid level.

 

In addition to the nissan factory service manual I pictured earler, here is subaru's version of purging a strut.

 

 

found in a subaru factory service manual.......

 

http://techinfo.subaru.com/downloads/STRUT_MOUNT.pdf?pdf=STRUT_MOUNT.pdf

 

I've read these exact same instructions contained within the boxes of factory shocks as well as popular aftermarket shocks and struts that I stocked in the mid-80s as well as in Nissan, Toyota, and Lexus factory service manuals.

 

I have no problem with your disagreeing with me but I'm having trouble believing that the factory service manuals for multiple car marques are incorrect.

[JMortensen]

The one thing that jumps out at me looking at the Subaru manual is the bit that says "If it is laid down, check for entry of air in the strut" this again tells me that the Subaru struts, like the factory Z struts, are not sealed pressurized units. They have the oil seal at the top, but if they were sealed air tight, then no air could get in. That's the only explanation I've got for you. If anyone has another sealed pressurized unit and can make it have a dead spot by flipping it over, I'd like to see that. Until I see that, I'll remain convinced that the experience I've had with the Illuminas and Bilsteins is generally correct.

[johnc]

Should they [Konis] come back out on their own because mine do not?

 

Koni 8610/8611s are not pressurized and the shock cycling/bleeding procedure HowlerMonkey lists above is needed before installation. In some cases you can shake the 8610 and hear the foot valve rattle if there's a lot of air in the shock.

 

FYI... the Koni 8610/8611 depends on the gland nut being tight on the insert for proper operation and to keep the top seal in good condition. If the gland nut gets loose the shock will not operate properly and the top seal will most likely fail. And when I say loose, I don't mean rattly loose; I mean lost torque. Keep the gland nut tight and check it often.

 

Any race shock (Koni, Bilstien, Penske, etc.) is NOT an install and forget part. When I ran the Konis they got pulled and inspected every year along with all the other suspension maintenance that's required between seasons.

Edited August 13, 2009 by johnc

[heavy85]

To follow-up after more investigation and the comments above. If held vertical they have good resistance but if laid down there are air pockets. These are the Koni 'Race' SA struts after a couple years of use. Jon - I dont think there is air from the atmosphere getting into the shocks, rather air from when they build them. The struts are filled with so much oil then there is an air pocket above the oil then they put the cap on. So it's built in air pockets above the fluid that are causing this. Here's an example: Say the pump feed supply hole is 1/4 the way up the oil chamber and the chamber is only filled 1/2 way with oil then when you invert the strut the feed hole is now above the oil level (now 3/4 the way up and the oil is only 1/2 way up) so you get no resistance because you're pumps air instead of fluid. Now if the oil feed holes were 1/2 way up and the chamber was filled 3/4 up with oil then even if you flipped it over the feed hole is always submerged in oil so it's not sensitive to orientation and you still get good resistance.

 

I've also done more testing and found my wheel bearing that although it's almost new is loose again and the strut does NOT have significant play in it. I ran yesterday with these Koni's and did very well so I think they are fine and will continue to run them. I have to take back any bad thoughts I had about the Konis.

 

Cameron

[JMortensen]

To follow-up after more investigation and the comments above. If held vertical they have good resistance but if laid down there are air pockets. These are the Koni 'Race' SA struts after a couple years of use. Jon - I dont think there is air from the atmosphere getting into the shocks, rather air from when they build them. The struts are filled with so much oil then there is an air pocket above the oil then they put the cap on. So it's built in air pockets above the fluid that are causing this. Here's an example: Say the pump feed supply hole is 1/4 the way up the oil chamber and the chamber is only filled 1/2 way with oil then when you invert the strut the feed hole is now above the oil level (now 3/4 the way up and the oil is only 1/2 way up) so you get no resistance because you're pumps air instead of fluid. Now if the oil feed holes were 1/2 way up and the chamber was filled 3/4 up with oil then even if you flipped it over the feed hole is always submerged in oil so it's not sensitive to orientation and you still get good resistance.

I understand the theory just fine, and I think there might be some shocks that have this issue, apparently the Koni is one of them. I think there are also shocks that are "open" to the surrounding air. It's been a long time since I've dealt with a stock Z shock, but I seem to remember that if you turned one of those over it will spill ALL of the oil out of the shock. The top seal was just to keep the shaft clean and wasn't air tight.

 

What I didn't like was the previous statement in this thread that if you flip a shock over it WILL have a dead spot in it, and that flipping a shock and compressing it is not a good test of the shock. With the shocks that I've used neither of those statements is true. The statement is just too absolute, and I think I've clearly proven it not true as an absolute statement. On the other hand, I was wrong when I told srgunz his Koni was dead when he flipped it and compressed it. I guess the moral of the story is that not all shocks are the same.

[johnc]

I understand the theory just fine, and I think there might be some shocks that have this issue, apparently the Koni is one of them. I think there are also shocks that are "open" to the surrounding air. It's been a long time since I've dealt with a stock Z shock, but I seem to remember that if you turned one of those over it will spill ALL of the oil out of the shock. The top seal was just to keep the shaft clean and wasn't air tight.

 

That might be true of a worn or damaged OEM 240Z shocks but I think they are designed to seal the oil inside the unit. I've disassembled probably a dozen 240Z struts with the stock OEM shocks that have been lying prone on a pallet in my shop for 5 years. Its hit or miss whether the units have any oil left inside when I go to tear them down. Some are completely full and make a mess despite my most careful efforts and others have just a tiny bit of oil left inside.

 

The factory gland nut has a double seal and a wiper.

[fentin_fury]

I am looking to purchase the bilsteins and have them re-valved. Slight issue in Canada - I would have to buy them, receive them, ship them back to bilstein, and have them returned. Anyone recommend a supplier more local that would ship to Bilstein for revalving then Canada?

[clarkspeed]

Another post for this very old sticky thread.

 

I pulled the Bilsteins out of my car after 3 years of moderate race use. They still looked and felt new. I've been happy with them. They are very durable. I sometimes wish they were adjustable, but I'm still making adjustments, changes, and upgrades to the car that are more important than shock tuning at this point. I just switched to bias ply Hoosiers and I'm dealing with completely different suspension settings now.

 

I sent them out for a rebuild and revalve and got the attached shock dyno. As you can see the valving is linear and more like 125/350 according to the graph. I did the unit conversions and generated the graph in Excel, so any errors are probably mine.

 

 

 

[thehelix112]

Did they revalve to 350/125 because you asked them to? Or did you ask for the 300/100 revalve? I assume thats not the stock valving?

 

Dave

[clarkspeed]

I ask for 300/100 and told them the application. I don't think replacing the valves is an exact science so they just approximate. It looks like it hits the 300/100 mark around 8 ips instead of 10.

[Dtsnlvrs]

More weirdness... I got the correct nuts when I ordered the B30-629 A1's, so thanks to Jeff on that one.

 

I called Ground Control because I thought they had monoballs that had the correct size hole in the center and didn't need an adapter. Turns out that is wrong, but they do have the adapter. So I got those ordered.

 

I was talking to Mike over there, and he said he ran these exact struts in his Z racecar back in the 80s and had nothing but problems with them, failure after failure. I relayed Keith's ideas about them, and he basically had a "that's not my experience" type of response. So I guess we'll see how they work out.

 

In addition he said that the top hats need some machining to fit. I was imagining that the 30mm strut shaft could be a problem and I could see that needing to be opened up, but he also said that the inner shoulder (I think he was talking about the inner hole's shoulder also needs to be cut back about .120" to fit the shape at the top of the strut shaft. He said he thought he had some instructions on how to install them and he was going to try and send them. If I get them I'll post them up.

 

I haven't heard anything like that from anyone here, so I'm a bit confused as to who is right and who is wrong. I suppose I'll figure it out when they get here and I go to install them. I'm thinking another option might be to find a different top hat, there are quite a few different ones available from Coleman Racing, for instance.

 

Does it never end???

 

Did Mike ever send you the instructions, or did you find a different top hat....I am looking to go the bilstein route with either the biscuit camber plate or the full on one (cant decide yet). I know Mike can get us the proper spacers and nuts for the shafts, but the top hats will be an issue. Just trying to see what I am getting myself into

[clarkspeed]

I recently installed some AZC camber plates in the rear. I sourced the top hats from a guy on ebay selling them for $11/ea. I had them machined to the dimensions I needed but you could probably get them close enough with a drill press.

[clarkspeed]

Here are some pictures of the top hats machined to accept the Bilstein Struts. I had to use a small spacer between the top hat and camber plate bearing to put the spring load on the bearing. I think the top hats I have in the front were sourced from Ground Control with their camber plates and they fit the struts fine although I may have opened them up slightly.

 

[JMortensen]

He did send me the instructions, I posted here but apparently the picture was lost in the software migration. I don't have the scans anymore. Suffice it to say that if you contact Ground Control they will sell you some spacers which fit the top shaft of the Bilsteins and the monoball and space it up about 1/2" to keep the thicker part of the shaft from interfering with the top hat. Then they have machined the center hole in the hat larger to allow clearance. They also put a spacer on top so that when you tighten down the nut on top it tightens against the spacer, not against the monoball itself. The top spacers are very thin, it's the bottom ones that do the work of spacing the strut shaft down and are thicker. With the spacers in place the Bilstein factory locknuts don't engage the plastic part of the locknut. That didn't bother me much since the last nuts I had were modified lugnuts and had no locking feature and never had a problem backing off.

 

I still think that some of the top hats that you find in Coleman Racing and similar places would work, but I haven't tried them so I can't say for sure that this works and that doesn't.

[JustinOlson]

Two years bump! Are there any new strut options worth looking at for a track car beyond what has been previously discussed in this thread?

[JustinOlson]

Interesting development from Bilstein that i'm curious about. It's really at the upper end of what I would spend on a non adjustable strut, but I am curious how well these 46mm struts would perform on a 240z:

 

 

 

http://www.bilsteinus.com/uploads/tx_templavoila/Bil_46mm_UniMtrsprtsStruts_flyer.pdf

[johnc]

Per Bret at Bilsiten Motorsports the 46mm would be overkill for a tarmac S30 but probably OK for a rally S30.  They are also working on a 36mm version in the same style.  That would be more appropriate for the S30 given the car's weight.