Rebuilding the front suspension
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raygreenwood
- Posts: 11910
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Lahti411
- Posts: 127
- Joined: Sat Jan 29, 2005 2:23 pm
I was rebuilding my other pair of front strut towers and noticed that if I use the adapter on top of the Audi cartridge and a spacer underneath it, the original bump stop will only slightly touch the cartridge cover plate. So it's the shock absorber that's going to bottom and not the bump stop.
I also noticed that the length of the Audi's cartridge rod movement is about the same as the lenght of an original replacement cratridges. So wouldn't I thus add another 62mm (this is the length of the part in the adapter that has a thread for the Audi cartridge) into the length of a cartdridge rod although I'm supposed lower the front. If I wanted that the original bump stop does it's job, shouldn't i then place the Audi cartridge to the bottom of the front strut tube and put a sleeve between the cartridge and the top cover?
I also noticed that the length of the Audi's cartridge rod movement is about the same as the lenght of an original replacement cratridges. So wouldn't I thus add another 62mm (this is the length of the part in the adapter that has a thread for the Audi cartridge) into the length of a cartdridge rod although I'm supposed lower the front. If I wanted that the original bump stop does it's job, shouldn't i then place the Audi cartridge to the bottom of the front strut tube and put a sleeve between the cartridge and the top cover?
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Lahti411
- Posts: 127
- Joined: Sat Jan 29, 2005 2:23 pm
Here's some quick renderings i made to show what i mean exactly:
Here's Audi shock with top adapter and bottom spacer
a close-up, the part with larger diameter is the bump stop spacer
Audi cartridge in a type 4 front strut
Original bump stop barely touching the cover plate when the shock absorber is fully compressed
Here's Audi shock with top adapter and bottom spacer
a close-up, the part with larger diameter is the bump stop spacer
Audi cartridge in a type 4 front strut
Original bump stop barely touching the cover plate when the shock absorber is fully compressed
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Bill K.
- Posts: 563
- Joined: Mon Oct 27, 2003 10:50 pm
I see your concern. Nice renderings - I now understand the idea 
Do you have the correct Audi cartridge? Strut rod extension dimensions from Ray?
Your assessment appears correct assuming the strut rod extension and bump stop spacer are correct - shorten the bottom strut insert spacer and add a top strut insert spacer to lower strut insert in the strut tube.
Alternatively assuming the strut rod extension is correct and the issue is with the location of the top spring plate on the strut rod, use the '74 bump stop without the bump stop spacer. This would lower the bump stop and top spring plate on the strut rod. OR modify the earlier bump stop spacer to lower it on the strut rod.
Ray WILL know.
Do you have the correct Audi cartridge? Strut rod extension dimensions from Ray?
Your assessment appears correct assuming the strut rod extension and bump stop spacer are correct - shorten the bottom strut insert spacer and add a top strut insert spacer to lower strut insert in the strut tube.
Alternatively assuming the strut rod extension is correct and the issue is with the location of the top spring plate on the strut rod, use the '74 bump stop without the bump stop spacer. This would lower the bump stop and top spring plate on the strut rod. OR modify the earlier bump stop spacer to lower it on the strut rod.
Ray WILL know.
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raygreenwood
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- Joined: Wed Jan 22, 2003 12:01 am
It appears your adaptor is waaaaay too long.
The adaptor lengths tarting from the top....the end the nut goes on which is the threaded pin:
(1) Threaded pin length to the shoulder where the top plate sits: 4.75" total with only the top 2.0" of the pin threaded
(2) The length of the larger diameter part where the plate sits below the top threaded pin: 2.450" total.
(3) Total length of the finished part: 7.20"
There appears to be too much sticking out beneath the bump stop spacer. What are your dimensions ? I can send you the file if I have not done so already. Ray
The adaptor lengths tarting from the top....the end the nut goes on which is the threaded pin:
(1) Threaded pin length to the shoulder where the top plate sits: 4.75" total with only the top 2.0" of the pin threaded
(2) The length of the larger diameter part where the plate sits below the top threaded pin: 2.450" total.
(3) Total length of the finished part: 7.20"
There appears to be too much sticking out beneath the bump stop spacer. What are your dimensions ? I can send you the file if I have not done so already. Ray
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Lahti411
- Posts: 127
- Joined: Sat Jan 29, 2005 2:23 pm
I made the adaptor by cutting it from an original 411 shock absorber rod. The total length should be exactly what you have given in the drawing, i've got from you earlier. So, the adaptor has original factory dimensions for the threaded pin, and the lower, thicker part of the adaptor is 2,45 inches (62mm) long. The lower part couldn't even be shorter as there would no more be enough material for the threaded pin of the Audi shock. The renderings are only to illustrate the problem: i didn't have the bump stop dimensions so it might be longer in reality. But anyway the problem is that the bump stop isn't doing what it's supposed to at the moment.
The bushings i've got won't slide over the thicker part of the rod like in this picture
The bushings i've got won't slide over the thicker part of the rod like in this picture
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wshawn
- Posts: 209
- Joined: Thu Dec 27, 2007 6:36 am
When I had this modification done last summer we had to machine out some of the metal bush inside the bump stop so that it would fit lower down over the wider part.
Not sure if that is what the problem is for you as well but it worked for me and the front end handles the bumps around here very well now.
Some of the problems are on one of my post when I asked Ray for help
http://www.shoptalkforums.net/viewtopic ... a4619963d2
Hope that helps you as the work is well worth the trouble to get right.
Not sure if that is what the problem is for you as well but it worked for me and the front end handles the bumps around here very well now.
Some of the problems are on one of my post when I asked Ray for help
http://www.shoptalkforums.net/viewtopic ... a4619963d2
Hope that helps you as the work is well worth the trouble to get right.
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raygreenwood
- Posts: 11910
- Joined: Wed Jan 22, 2003 12:01 am
One thing that may help that may not be in some of my posts. You will need to cut off...about 3/8" to 1/2" of the very top of the threaded part of the new Audi strut cartridge.
I trimmed mine with an angle grinder until the large diameter face of the strod rod makes up perfectly flat to the wide part of the bottom of the strut adaptor.
The length of all of teh dimensions of this strut adaptor were very carefully worked out. It took a couple of trials to get it right. It is the correct length to get the correct stance and leveling...plus just a reasonable amount of extra spring compression. If you make the main body of the adaptor longer for any reason...it will not give the leveling you want. If you make it shorter...you have reach problems.
But...you will have to trim off a bit of the threaded part of the Audi strut to make it make up flush. If it does not fit flush...it can snap the threaded rod off of the Audi strut cartridge due to side loading.....I did that. It sucked.
You will also need to be careful on teh finished length of teh adaptors top thread. Depending on the thickness of washers and teh make of the strut bushing you can be up to 1/2" too long of thread sticking out the top.
Trim it with a dremel and install a new slot in the top.
The risk of having the thread too long...is that when you go over a bump and the strut bushing flexes....it will put two ugly dents in your hood......been there!
I had bump stop bushings that fit...and a couple that needed grinding out to fit.
After I drove for a while ...I finally realized that I really did not need that massive factory bump stop that was impossible to find new boots for.
I installed an aftermarket one from a generic set from Pep boys with a little mod work...that had a nice boot and fits tight around the stock .
If you opt NOT to use the stock steel bump stop bushing....you will notice that teh strut rod thread protrudes too far from the top...and lowers your suspension too far and compresses the spring too much. In this case....you can simply use stacks of steel arbor bushings to set it up to what you consider good and sane....in place of that bushing....and then again...trim the top threaded stud length accordingly. Ray
I trimmed mine with an angle grinder until the large diameter face of the strod rod makes up perfectly flat to the wide part of the bottom of the strut adaptor.
The length of all of teh dimensions of this strut adaptor were very carefully worked out. It took a couple of trials to get it right. It is the correct length to get the correct stance and leveling...plus just a reasonable amount of extra spring compression. If you make the main body of the adaptor longer for any reason...it will not give the leveling you want. If you make it shorter...you have reach problems.
But...you will have to trim off a bit of the threaded part of the Audi strut to make it make up flush. If it does not fit flush...it can snap the threaded rod off of the Audi strut cartridge due to side loading.....I did that. It sucked.
You will also need to be careful on teh finished length of teh adaptors top thread. Depending on the thickness of washers and teh make of the strut bushing you can be up to 1/2" too long of thread sticking out the top.
Trim it with a dremel and install a new slot in the top.
The risk of having the thread too long...is that when you go over a bump and the strut bushing flexes....it will put two ugly dents in your hood......been there!
I had bump stop bushings that fit...and a couple that needed grinding out to fit.
After I drove for a while ...I finally realized that I really did not need that massive factory bump stop that was impossible to find new boots for.
I installed an aftermarket one from a generic set from Pep boys with a little mod work...that had a nice boot and fits tight around the stock .
If you opt NOT to use the stock steel bump stop bushing....you will notice that teh strut rod thread protrudes too far from the top...and lowers your suspension too far and compresses the spring too much. In this case....you can simply use stacks of steel arbor bushings to set it up to what you consider good and sane....in place of that bushing....and then again...trim the top threaded stud length accordingly. Ray
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wshawn
- Posts: 209
- Joined: Thu Dec 27, 2007 6:36 am
I'll vouch for that one too!raygreenwood wrote:
The risk of having the thread too long...is that when you go over a bump and the strut bushing flexes....it will put two ugly dents in your hood......been there!
However when the weather improves I have a new (well, not new, but rot free) bonnet to paint and fit.
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raygreenwood
- Posts: 11910
- Joined: Wed Jan 22, 2003 12:01 am
Lahti411....in looking at your renderings...you are not too far off. You end up with a shorter stroke on the strut rod than stock has...because you don't need it.
The 411/412 NEVER bottoms out its bump stop. Its physically impossible because the strut rod itself bottoms out in the casing before that happens. The 411/412 uses a grand total of about 4.5" of stroke even at extremes.
On the Audi strut......you have more than enough especially since the audi strut is stiffer and your spring now has more pre-compression. Ray
The 411/412 NEVER bottoms out its bump stop. Its physically impossible because the strut rod itself bottoms out in the casing before that happens. The 411/412 uses a grand total of about 4.5" of stroke even at extremes.
On the Audi strut......you have more than enough especially since the audi strut is stiffer and your spring now has more pre-compression. Ray
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Lahti411
- Posts: 127
- Joined: Sat Jan 29, 2005 2:23 pm
Lahti411....in looking at your renderings...you are not too far off. You end up with a shorter stroke on the strut rod than stock has...because you don't need it.
The 411/412 NEVER bottoms out its bump stop. Its physically impossible because the strut rod itself bottoms out in the casing before that happens. The 411/412 uses a grand total of about 4.5" of stroke even at extremes.
On the Audi strut......you have more than enough especially since the audi strut is stiffer and your spring now has more pre-compression. Ray
Ok, this is infact what i was guessing my self. I trimmed the Audi cartridge a bit already earlier and it fits flush with the adaptor. I also checked the dimensions for the top adaptor once again and everything was as in your drawings. I guess i can now continue my rebuild.
Thank You Ray!
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raygreenwood
- Posts: 11910
- Joined: Wed Jan 22, 2003 12:01 am
Keep us posted.
One thing that is crucial to good handling I may not have mentioned. Get an old car tire inner tube or buy some thin rubber sheet. You need to take a strip of it about 2" wide. Wrap it around the strut cartridge housing down low about 4" from teh bottom of the Audi strut cartridge. Wrap it, and test fit it into the 411/412 outer strut tube. When you have the length cut right, spray one side with contact cement and wrap it tight.
What you are looking for is a to make a rubber buffer ring. this keeps the bottom of the Audi strut cartridge from swaying side to side in the bore. The centering ring at the top does the same for the top...but one is needed near the bottom. This is a very large problem for type 4 and any strut handling.
On the original oil strut cartridges...we did not quite have the problem because the bottom of the strut tube...fit the bottom curve of the outer strut tube pretty well.....though they still had some of this problem. The aftermarket normal 411/412 replacement cartridges from KYB, Boge, Monroe and Knoi...do not. Neither does teh Audi GR-2 cartrdige. This is a major handling improvement. It gets rid of some mushiness through sweeping curves....that happens as strut cartridges shift inside the strut tube. Ray
One thing that is crucial to good handling I may not have mentioned. Get an old car tire inner tube or buy some thin rubber sheet. You need to take a strip of it about 2" wide. Wrap it around the strut cartridge housing down low about 4" from teh bottom of the Audi strut cartridge. Wrap it, and test fit it into the 411/412 outer strut tube. When you have the length cut right, spray one side with contact cement and wrap it tight.
What you are looking for is a to make a rubber buffer ring. this keeps the bottom of the Audi strut cartridge from swaying side to side in the bore. The centering ring at the top does the same for the top...but one is needed near the bottom. This is a very large problem for type 4 and any strut handling.
On the original oil strut cartridges...we did not quite have the problem because the bottom of the strut tube...fit the bottom curve of the outer strut tube pretty well.....though they still had some of this problem. The aftermarket normal 411/412 replacement cartridges from KYB, Boge, Monroe and Knoi...do not. Neither does teh Audi GR-2 cartrdige. This is a major handling improvement. It gets rid of some mushiness through sweeping curves....that happens as strut cartridges shift inside the strut tube. Ray