Struts...

In our Audi's we have found over the past couple years the greatest area that needs to be improved for our cars is the struts.

Currently we work with Koni and they have been absolutely wonderfull. I would like to continue working with them however we are certainly open to other options. Just to help me understand a bit when I talk to them again and/or if we talk to another company I would like to explain what I understand our problem to be and I would greatly appreciate any feedback that you or a friend may have. Once again we also are looking for recomended companies to work with in addition to Koni. Basic point is we want something that will work without failing and fits into a reasonable budget (if you are a company represenative viewing the forum, partial or full sponsorships are always an option to keep things affordable).


ok the log winded issues:

In 2 sessions the rebound valving will fail on the struts, leaving only compression. As you continue to race on the struts they progressively get worse in the fact that the shaft will start to pivot side to side in addition to its normal up and down motion. The following picture illistrates in my mind a rough idea of what is happaning. Please feel free to edit/fix if I am incorrect in any part of my non-epert thoughts and diagrams.

- the yellow is the outer strut housing - Not to be confused with the strut housing on the car... this is a strut out of the car on the bench!!!

- the grey is the shaft that moves up and down
- the blue is the inner wall that the shaft moves up and down within.
- the red are the valves
- the black is the upper seal/cap that holds the insides in and the outsides out (including the oil).

My understanding is that as those red valves wear (as illistrated in drawing "C" the entire internal parts of the strut begin to pivot on the upper seal/cap of the strut. (black part).

http://www.rstperformance.com/Strut%20Problems.jpg

Picture "A" illistrates what the strut looks like new along with its movements.
Picture "B" illistrates my version of what the internal parts of a strut looks like and its hardware (not oil)movements.
Picture "C" illistrates my version of what the internal parts look like after wear and how the hardware (not oil) moves due to the wear.
Picture "D" illistrates what the strut looks like after wear along with its movements.

* It is important to know that the "yellow" part of the strut is the housing and is not moving in the illistrations.


Again, thank you for any help/advise you can offer. I would love to get somethign that would work and can handle the side load our cars creat on the strut due to thier unique suspension geometry.

Thanks again;

Raymond "Maybe we can all learn something" Blethen

Doesn't Shine make some trick pieces for this car?

Otherwise, I would call Matt Kessler at Kessler Engineering. He has worked with Greg Amy on the NX2000 and designed and built the struts on that wicked ITA car.

You are entering 'not cheap' territory. Have fun!

EMAIL: [email protected]

Phone: 203-265-1602 or 203-444-1467

AB

It seems as though you might need to consider inverted struts, most likely a custom job.

Most people we have talked to say put in Bilstiens as they are more "heavy duty." Our budget certainly can't afford "custom" designs. Especialy trial and error ones where you are spending $500 + per strut only to have it fail without warrenty.

Any idea what the price range is for "custom" stuff to be built? I know it can get crazy, but all we want is something simple not perfect "dampaning" but at least will work enough to keep the wheels pointing where they are suposed to when we align the car!!!

Raymond

PS: Shine makes some stuff, but not struts.

I've had good luck w/ground control....and there's one particular yellow vw with a very aggressive (ie kurb hopping ) driver :) that uses them also...who I'm still trying to catch.. B)

yeah, the advanced design struts claim to be very durable, i haven't any first hand knowledge but am considering them for my "new" car.

Huge Buckaroos to solve your issues.

Raymond,
We have had extremely good luck with Carerra shocks and springs (No sponsorship, but would love some!)
From what you describe, it sounds like your shocks are taking stress that your springs should? Stiffer springs?
Good luck!
Mark "I have no clue what I'm talking about, but it sounds good" Larson

What do these guys use?
http://www.audi.com/etc/medialib/cms...0587.Image.jpg

Quote:

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In our Audi's we have found over the past couple years the greatest area that needs to be improved for our cars is the struts.

Currently we work with Koni and they have been absolutely wonderfull. I would like to continue working with them however we are certainly open to other options. Just to help me understand a bit when I talk to them again and/or if we talk to another company I would like to explain what I understand our problem to be and I would greatly appreciate any feedback that you or a friend may have. Once again we also are looking for recomended companies to work with in addition to Koni. Basic point is we want something that will work without failing and fits into a reasonable budget (if you are a company represenative viewing the forum, partial or full sponsorships are always an option to keep things affordable).
ok the log winded issues:

In 2 sessions the rebound valving will fail on the struts, leaving only compression. As you continue to race on the struts they progressively get worse in the fact that the shaft will start to pivot side to side in addition to its normal up and down motion. The following picture illistrates in my mind a rough idea of what is happaning. Please feel free to edit/fix if I am incorrect in any part of my non-epert thoughts and diagrams.

- the yellow is the outer strut housing - Not to be confused with the strut housing on the car... this is a strut out of the car on the bench!!!

- the grey is the shaft that moves up and down
- the blue is the inner wall that the shaft moves up and down within.
- the red are the valves
- the black is the upper seal/cap that holds the insides in and the outsides out (including the oil).

My understanding is that as those red valves wear (as illistrated in drawing "C" the entire internal parts of the strut begin to pivot on the upper seal/cap of the strut. (black part).

http://www.rstperformance.com/Strut%20Problems.jpg

Picture "A" illistrates what the strut looks like new along with its movements.
Picture "B" illistrates my version of what the internal parts of a strut looks like and its hardware (not oil)movements.
Picture "C" illistrates my version of what the internal parts look like after wear and how the hardware (not oil) moves due to the wear.
Picture "D" illistrates what the strut looks like after wear along with its movements.

* It is important to know that the "yellow" part of the strut is the housing and is not moving in the illistrations.
Again, thank you for any help/advise you can offer. I would love to get somethign that would work and can handle the side load our cars creat on the strut due to thier unique suspension geometry.

Thanks again;

Raymond "Maybe we can all learn something" Blethen
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Raymond,

The "red" valves are know as the foot valve. They're there to compensate for the fact that the movement of the piston rod chages the volume of the upper chamber. Most gas shocks such as Bilstein's use a high pressure nitrogen chamber to vary the lower volume, however Koni's (even their single adjustables) still use the foot valve for rebound with the high pressure gas in the outer annular chamber. Sounds to me that the real problem is hyper-extending of your struts, and then applying a bending moment. Struts and motorcycle forks both depend on sliding bearings for wheel location; however, when the strut or fork is extended the distance between the bearing supports is small and a side load is applied the internal bending moment on the bearings is greater than most materials used for this application can stand. Thus once damaged it only gets worse with time. This is probably related to removal of the elastimer at the top strut mount, then reinforcing the structure. All the bending loads and side impacts go directly into the strut bearings with out anything to soften it. What to do? I'd consider installing some form of polyuerathane or delrin upper sturt bearing to take the impact, besides it's easier and chaper to change the upper strut mount than it is to change the sturt. Good luck,

James

Quote:

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Raymond,

The "red" valves are know as the foot valve. They're there to compensate for the fact that the movement of the piston rod chages the volume of the upper chamber. Most gas shocks such as Bilstein's use a high pressure nitrogen chamber to vary the lower volume, however Koni's (even their single adjustables) still use the foot valve for rebound with the high pressure gas in the outer annular chamber. Sounds to me that the real problem is hyper-extending of your struts, and then applying a bending moment. Struts and motorcycle forks both depend on sliding bearings for wheel location; however, when the strut or fork is extended the distance between the bearing supports is small and a side load is applied the internal bending moment on the bearings is greater than most materials used for this application can stand. Thus once damaged it only gets worse with time. This is probably related to removal of the elastimer at the top strut mount, then reinforcing the structure. All the bending loads and side impacts go directly into the strut bearings with out anything to soften it.
James
[/b]

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Thanks for the reply, that is exactly what is happaning I think...

Quote:

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What to do? I'd consider installing some form of polyuerathane or delrin upper sturt bearing to take the impact, besides it's easier and chaper to change the upper strut mount than it is to change the sturt. Good luck,
[/b]

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At the top mount we have camber plates with spherical bearings... you suggest replacing the sperical bearings with some sort of delrin bushing?


Also since my post I have talked with a few people (Thank you!!!) and many people suggest that part of our issue is that we are using a strut that uses a twin tube technology. From what I have been lead to believe a mono-tube strut/shock is far more durable than a twin tube.

If I were going to do a "custom job" strut I would think another thing to do to help with the side load issue would be to have a longer rod guide (upper seal in my diagram) along with a larger diameter Piston Rod (grey area in my past diagram). By having the larger diameter piston rod I would probably have to change over the the monotube technology.

I have checked out a few different suppliers and as of now I am really interested in the bilsteins simply because it looks as though I can completely rebuild them myself should I notice that they are starting to fail. The Bilsteins also look like they would be cheeper to make a "custom" strut as you can purchase pieces individually. I havn't checked out any prices yet, as I want to have all the measurments/dimensions figured out before I make a call. Does anyone have experience with rebuilding the Bilstein shocks/struts on thier own? How is/was the experience? What are the costs of pieces parts? Also does anyone know of other businesses that make rebuildable struts/shocks?

Thanks everyone for all the help!!!

Raymond "learnin" Blethen

I'd consider it; however, my car's got a very similar setup with a plate/mono bearing. What series Koni are you running? Unless you run with an external resovoir I doubt you'll find a double adjustable strut that's mono tube, after all you have to have a way of applying several hundred psi of nitrogen as well as vary the flow in both directions. Mr. glassburner mentioned GC, but they use Koni's too, but it might be that you're using a strut that operates too close to the top of it's travel, in other words too short.

James

Raymond, I have modified struts with Bilstein inserts which have hellfer big strut cap nuts as compared to the OEM strut cap nut. I did the deal the easy method & bought proven modified struts from ISC Racing in FL. Ya might call Mike Vansteinberg the owner of ISC Racing.

Have Fun ;)
David

Bilstein will revalve most of their struts (HD, Sports, Rallye, etc.) for little $. Just requires mailing to Calif. If you haven't bought them yet, call first to make sure that they're revalvable. The Bilstein monotubes seem to take lateral bending forces a lot better than other off-the-shelf struts. Part of that is just the larger diameter of the "shaft" (which is really the strut body since they're inverted). I would guess that you could get a new set of HDs (no need to spend more on Sports or Rallyes since you're getting them revalved anyway) and have them revalved by Bilstein for race spring rates for under $800 (including struts, all 4 corners). If you just need the fronts, probably under $500 total.

EDIT: Careful here, I think Bilstein's "TC" series are NOT revalvable (and maybe not monotube for that matter).

Raymond...

I looked and looked for Bilsteins for the Coupe. Turns out they don't make a sport shock right now for these cars, so I managed to source some used Bilstein sport front shocks made for an Audi 4000 quattro. They fit the housings and have the inverted design. For the rears, again, couldn't find a listing for Bilsteins for the coupe, so I had some blown out VW Rabbit rear Bilstein Sports and as it turned out, they fit the CGT as well.

Now that I had "cores", I wanted them revalved to handle the "Blethen" spring rate setup and so I called Bilstein in California (they also have an office on the east coast, I later found out). I talked to Jack (competition / rebuild supervisor at 858-386-5900) and told him what I wanted. He had me fill out a sheet with the exact specs for the car and what rates I'd be using, then I sent them in. I didn't have an exact idea of what rebound / compression I should be using, so I left it up to the techs there.

It took two weeks and they completely custom-valved the set for the car. It would have been $65 a corner for the rebuilds, but the shafts on the rear were bent, so I asked them to replace the 12mm shafts with 14mm units. That cost a bit more because they had to do some machining, but seemed a bit sturdier.

The only thing I had to do was trim the bumpstops (which are actually on the_inside of the hollow tube that's normally the bottom of the shock). I've got pics if anyone wants to see what they look like.

Anyway, all said and done, the shocks seem really well suited to the suspension and really made a difference on the car. I've only got one weekend on them thus far, so I can't comment on how well they take abuse just yet either. My car sits a bit higher than yours (ok, quite a bit), so you might have to talk with Jack about that (shortened stroke / shaft?), but it might be worth a try.

Seems to be reasonably priced and I believe he told me that they can rebuild just about any "non-crimped" shell Bilstein whether they're HD's or Sports or whatever. Potentially that means you could find used units from people then have them revalved at will like you want them...

You probably could have found new Bilsteins for your Audi in Europe, but its good to hear that you found something to work with.

I get my race struts from the UK; they are AVO(s).

Cheers.

I should have updated this...

We have decided to give Bilstein a try. They have proven to be great to work with and have given us an option that we couldn't refuse or at least try. I want to thank everyone for their input and suggestions. You certainly played a role in what direction we have gone in, and this page will be saved for future reference should things not work out. The big test will be to see if the struts will hold up after a couple days of use. I will most definatly report back our findings.

I would like to make a special thank you to Bildon Motorsports for taking the time to talk to me about a few different options. I strongly suggest anyone racing an Audi and/or VW check them out to see what they might have to help you get to the finish line first. :smilie_pokal: Bill without a doubt certainly knows his stuff!!! :023:

I also will not through Koni under the bus as they have helped us tremendously over the past 5 years and they do have some wonderful products, unfortunatly we are not confident that they have what we need at a price that we can afford at the present time. Again thank you Koni :035:

Raymond