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adamharo
Samba Member
Joined: October 18, 2012
Posts: 33
Location: Fresno Ca
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 Posted: Mon Dec 02, 2013 3:07 pm Post subject: Front end shimmy |
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Hey Guys.
My 411 has developed a shimmy between 40-50mph. It's gets pretty bad at times. I had the balance checked on the tires and they are fine. I jacked it up one side at a time and and there is some play. When I wiggle the tire the whole structure, tire, strut etc..., move. It seems like it is something up towards the middle. Any thoughts on what to look for when I dig further into it this weekend? It doesn't seem to be the ball joints or anything down by the tire itself.
Thanks
Adam |
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19super73
Hardcore Stock Nazi
Joined: October 18, 2007
Posts: 4351
Location: Cité Soleil
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adamharo
Samba Member
Joined: October 18, 2012
Posts: 33
Location: Fresno Ca
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| Posted: Tue Dec 03, 2013 10:55 am Post subject: |
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| Thanks Super73, that helps. |
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19super73
Hardcore Stock Nazi
Joined: October 18, 2007
Posts: 4351
Location: Cité Soleil
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sallittjob
Samba Member
Joined: September 16, 2010
Posts: 340
Location: North NJ
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| Posted: Thu Jul 27, 2023 9:27 am Post subject: Re: Front end shimmy |
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Hi Everyone,
My 73 412 4 Door Sedan had a decent shimmy at 45-55mph when I bought it last year. Over the course of the past few months, I did the following:
-Replaced the steering damper (OG had completely failed).
-Replaced the Idle Arm bushing with a solid bushing.
-Replaced center link and tie rod ends.
-Replaced the control arm bushings with new Delrin ones I machined.
-Checked the centering ring and rear control arm bushings, for play, they were intact believe it or not and feel really tight when I pry on them.
-Struts seem to be good. The car rebounds very quicky when you push on a corner of the bumper with no bounce.
-Checked steering box and found no excessive play.
-Aligned the front end of the car.
-Checked the balance of the front tires.
-I can't see any bend in the wheels when I spin them, so I don't think that's the issue.
The shimmy is very minimal now but still present and it's driving me nuts. Filling up the gas tank basically eliminates the shimmy until you get to a half tank or so.
I'm not sure what could be causing the shimmy at this point. Any pointers would be appreciated!
Thanks
_________________
57' Beetle Deluxe
1192cc SP
71' Super Beetle
1968cc DP
73' 412 Sedan
1679cc FI
75' Westy
1800cc FI |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Thu Jul 27, 2023 12:06 pm Post subject: Re: Front end shimmy |
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| sallittjob wrote: |
Hi Everyone,
My 73 412 4 Door Sedan had a decent shimmy at 45-55mph when I bought it last year. Over the course of the past few months, I did the following:
-Replaced the steering damper (OG had completely failed).
-Replaced the Idle Arm bushing with a solid bushing.
-Replaced center link and tie rod ends.
-Replaced the control arm bushings with new Delrin ones I machined.
-Checked the centering ring and rear control arm bushings, for play, they were intact believe it or not and feel really tight when I pry on them.
-Struts seem to be good. The car rebounds very quicky when you push on a corner of the bumper with no bounce.
-Checked steering box and found no excessive play.
-Aligned the front end of the car.
-Checked the balance of the front tires.
-I can't see any bend in the wheels when I spin them, so I don't think that's the issue.
The shimmy is very minimal now but still present and it's driving me nuts. Filling up the gas tank basically eliminates the shimmy until you get to a half tank or so.
I'm not sure what could be causing the shimmy at this point. Any pointers would be appreciated!
Thanks |
Struts "seem" to be good.....is what is wrong.
A couple of things:
1. You noted that you replaced the centerlink. Thats good, but just to be sure, is this a new centerlink or a good used one? Also, even if its new...which means NOS....all of these DS858 parts have the seeds of their own demise built into them (the nylon packings).
All of them are now at least 40 years old in the box. The lifespan was poor when new. Its worth carefully removing yours to check for play in the rotating studs. When you remove these with a "pickle fork" tool, put the angled side of the fork on the idler arm and steering box to keep from mashing up the outer seal.
2. The indicator that your struts are an issue is that when you fill up the tank...or alternately you could put 80-100 pounds of weight in the trunk against the vertical wall to duplicate this....the shimmy goes away.
What this is doing is compressing your suspension (meaning the strut itself) to a point where there is less wear on the internal seals and better sealing and control or better oil supply internally.
This also loads out your strut mounts and bushings differently and takes up teh small amount of slack/slop that the factory and aftermarket struts had between cartridge and strut tube.
The issue is that the struts are either original oil bath struts from the factory....which by this time are sure to be low on oil and also for sure the .....or aftermarket cartridge style strut cartridges....which are likely leaking from the top seal by this time.
The brands you will probably find on this continent are Monroe, KYB, Sachs, Boge...maybe Wagner.
The other issue being that these will be some form of either original factory or aftermarket.....is that both will be old beyond correct ability to be used.
The last manufactured original aftermarket strut cartridges for 411 and 412 were KYB and they stopped production in 1989.....34 years ago.
Virtually all NOS aftermarket strut cartridges I found at and since about the 20 years of age mark are pretty much dead. Let me expand on that. They are all oil and so work fine when you install them. But the upper seal is 30+ years old. You might get 30k miles. You typically get 5-7k miles.
And....if these are 30-40 year old strut cartridges or even older factory oil bath struts....that means that they have not been apart in that long and usually this means that the strut bushings and bearings are way past time for replacement.
Both of these issues can cause shimmy.
The issue of FAST strut rebound was partly from the original factory valving (the rebound valving was poorly calculated).....and that was faithfully reproduced by all of the aftermarket cartridges.
It was weak on rebound valving which causes excessive rebound when you hit bumps. It gets worse as the strut loses oil through leaking seals.
It causes shimmy at certain speeds because the inability to keep the tread in contact with the ground as it goes over fine ripples.
The strut bearing/bushing being shot causes teh same effect.
3. The other common issue...especially if your 412 was found sitting someplace for years....is wheel rim "spread".
Finding this was the key to finally getting rid of teh last oscillation. If a car sits on flat tires for a couple of years or more.....it flat spots the rims by causing a very small spread between the outer rims.
The only way to see this is to dismount the tire and put your eyes in line with the centerline and rotate it on the tire machine slowly.
This combined with any weakness in teh rebound ability of old struts...causes a vertical oscillation that cannot be controlled at certain speeds.
Oh....almost forgot:
It could simply be that your alignment is off. About 90% of the time over the years , the shops could not properly align my 411's and 412's. If you aligned it with a low gas tank and nothing in the trunk....its not aligned properly. This changes the static castor.
Alignment shops forget that there is nothing the front end. And, most of them lift the front end too high during the turning castor check....and then do not let it back down before setting toe-in. There is not actually any reason to lift the front end of a super beetle or 412 when checking the turning castor. There is not enough weight to cause turning issues and need to lift the front end.
Ray |
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412STi
Samba Member
Joined: September 25, 2015
Posts: 23
Location: Germany
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| Posted: Sat Jul 29, 2023 2:10 am Post subject: Re: Front end shimmy |
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Hi
I think Ray is right.
The shock absorbers and similar parts are ancient (even if they were never installed)
What is on the market today is mostly old stock and outdated.
30 years ago I had KONI make dampers for my Variant specifically for lowering. I didn't drive it long and after 30 years of standing still, they're still scrap.
For my reconstruction I will use Spax dampers because they are made new to order. I could have the old ones overhauled at KONI, but that would only make sense if there were no alternative.
Originals would also be overhauled, but only if all the sealing rings ect. be replaced.
_________________
Gerold
The morning brings a mystery, the evening makes it history
The oil can not be, was none in it. |
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412STi
Samba Member
Joined: September 25, 2015
Posts: 23
Location: Germany
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sallittjob
Samba Member
Joined: September 16, 2010
Posts: 340
Location: North NJ
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| Posted: Mon Jul 31, 2023 11:50 am Post subject: Re: Front end shimmy |
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Very cool. I'll check them out!
Going through Ray's list, the most likely culprit at this point seems to be the struts. Is there any way to test them in the car or do I just have to assume they are shot and replace since they're original?
_________________
57' Beetle Deluxe
1192cc SP
71' Super Beetle
1968cc DP
73' 412 Sedan
1679cc FI
75' Westy
1800cc FI |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Tue Aug 01, 2023 7:26 am Post subject: Re: Front end shimmy |
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| sallittjob wrote: |
Very cool. I'll check them out!
Going through Ray's list, the most likely culprit at this point seems to be the struts. Is there any way to test them in the car or do I just have to assume they are shot and replace since they're original? |
There are some things to inspect.
1. Lift up the car so you can work under the fender and with a long screwdriver, lift the strut boot and inspect the top screw cap of the strut body. If there is any oil mixed with dirt caked around the rod where it pokes through the strut cap....the rod seal has been leaking and you have lost oil.
Long ago I posted a crudely drawn but accurate diagram of the fluid flow inside of the factory oil bath struts. I will dig up the link and post it here.
Marvelous but complex design that cannot stand either an excess or shortage of the CORRECT viscosity hydraulic fluid.
When you have the old factory oil bath type, and the top seal starts leaking, you will find a lot of oil all around the strut cap. When you have aftermarket cartridges, it mostly stays around the top opening where the rod comes through the cap and most of the oil leaks down into the strut body.
If your boot is torn or missing.....your seal is shot from the dirt on the rod seal.
2. Really there is not any reason to test them even if you had a strut actuating dyno and even knew the specs to test for. No matter what you find, they are shot.
The factory struts for 411 and 412 were poorly calibrated even when new and had a very short active life in miles before rebound became excessive and it started wearing tires or caused handling and vibration issues.
The build quality of the factory struts was excellent. Really as long as the seal stays intact and fluid never leaks out or gets water in it......they could last forever....with their poor strut valving.
The aftermarket struts back in the day...were also very well made....and accurate to the factory valving....which made them just as much of a wear and handling issue even though they were 4X less cost than dealer.
3. The problem with the valving is that the front spring rate on 411 and 412 was HUGE. In fact the front springs are HUGE and LONG. The front springs on my 412 are twice the size as those on my Golf or Jetta and those cars have an engine and transmission up front and outweigh a 412 by about 1000 lbs.
The 411 and 412 and even somewhat the super beetle all suffered from early MacPherson strut design issues. They just did not know yet.
Our cars had huge trunks in the front. They made the springs large and progressive to handle lots of luggage weight.
The strut valving design has less rebound damping than it should have because it assumed that most of the time that front trunk would be somewhat full.
The problem is that if they had added more rebound.....or enough rebound.....when you did have the trunk loaded....the front end would then have too little rebound and when loaded....and driving over successive ripples.....think like a set of double railroad tracks.....it causes an internal pumping action that actually Jack's the front end downward until it bottoms out hard.
That scenario I learned about when experimenting with tweaking the valving on factory oil bath struts and/or using oil that is not the exact viscosity.
What was required was better spring calibration....which you can achieve by lowering that nose high attitude to level....along with adding more rebound and compression valving at the same time.
I got lucky and found that combination with the Audi strut cartridge mod.
4. The other inspection you can do.....is lift the tire all the way off the ground. With a flashlight, get your head up as close to the strut mount as you can.
On 411 or early 412 with symmetrical bolt pattern strut mounts, they are bonded rubber bushings. With the strut fully extended you will see the radial cracks in the rubber bushing from below.
On later asymmetrical bolt pattern bushings, with the car on the ground, you can simply measure how much play between the upper cap that is undef the top strut rod nut and the steel strut mount body and whether it is axially straight or tilted off to one side.
If you find bushings shot.....that will cause a shimmy on its own....and since they are usually the same age as the rest of the strut.....it pretty much means replace it all.
Lately, a few have posted here that Bilsteins for 411 and 412 are now available. I have no experience with them. I also asked whether they came with an adapter bushing kit and never got an answer.
The link that was posted states they fit all years.....which would be incorrect without a detailed bushing kit....because there were 3 different strut mounts from 1968 to 1974 and two different strut rod designs and three different bump stops.
I believe they are Bilstein B4 series which should be OEM valve rate gas.
Long ago I looked at Spax. At that time they had no 411/412 specific offerings. If they do now, that is excellent.
My problem with either of these....Bilstein or Spax....is the question of whether the valving fixes the original strut poor rebound valving and/or does it get rid of that "nose high" attitude which is part of the handling issue.
For what it's worth, I found that back in the day, when I had new aftermarket Monroe, Boge or KYB strut cartridges....meaning I know they were good and all else was good with the suspension.....I could counteract both the valving issues and the nose high issues and get good driving.....
By putting about 125 to 150 lbs of weight (mostly tool boxes and spare parts, in the trunk and as close to the headlights as possible. Ray |
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sallittjob
Samba Member
Joined: September 16, 2010
Posts: 340
Location: North NJ
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| Posted: Tue Sep 19, 2023 6:45 am Post subject: Re: Front end shimmy |
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I wanted to close the loop with an update.
Over the weekend I rotated my front tires to the rear and my rear to the front in hopes of eliminating the wobble if it were due to "wheel spread" on one of the front wheels. I'm happy to report that there is zero wobble now in my front end. I can't feel any ill effect from moving the problematic wheel to the rear, so I'm calling it fixed for now. Got the 412 up to 70mph and it felt tight and smooth. Like driving on rails 
Take note if you are chasing your tail with a front end shimmy after confirming everything is tight in the front suspension.
Thanks all for the help, especially Ray for the detailed list of common sources of shimmy.
Time to finally enjoy driving the car this fall after basically a year of repairs.
-Chris
_________________
57' Beetle Deluxe
1192cc SP
71' Super Beetle
1968cc DP
73' 412 Sedan
1679cc FI
75' Westy
1800cc FI |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Tue Sep 19, 2023 10:12 am Post subject: Re: Front end shimmy |
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| sallittjob wrote: |
I wanted to close the loop with an update.
Over the weekend I rotated my front tires to the rear and my rear to the front in hopes of eliminating the wobble if it were due to "wheel spread" on one of the front wheels. I'm happy to report that there is zero wobble now in my front end. I can't feel any ill effect from moving the problematic wheel to the rear, so I'm calling it fixed for now. Got the 412 up to 70mph and it felt tight and smooth. Like driving on rails
Take note if you are chasing your tail with a front end shimmy after confirming everything is tight in the front suspension.
Thanks all for the help, especially Ray for the detailed list of common sources of shimmy.
Time to finally enjoy driving the car this fall after basically a year of repairs.
-Chris |
Isn't that amazing? Flat spotted tires and spread rims can do that and are ao hard to diagnose.
One thing to also remember. Having a minor glitch like a a0read spot on a rim....a really small one....can be thought of as a diagnostic tool of sorts when put on the front end.
The rear end has more weight, heavier springs and less moving parts. As long as it in decent shape with good shocks, it can handle or "tame" a very minor flat spot.
But the front end "should" be able to as well....but even when the front end condition seems pretty nominal....the flat spot on a rim will cause issues...pointing out some things to check.
Items to check in the front end first.....centerlink....idler arm bushing (if it's not bronze, replace it) ....strut mount assemblies. There are a few other little things that can cause oscillations but start with these 3 things.
Ray |
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lateral
Samba Member
Joined: August 21, 2012
Posts: 45
Location: Sydney Australia
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| Posted: Sat Oct 21, 2023 5:42 pm Post subject: Re: Front end shimmy |
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Hi everyone,
I would just like to add a brief update to me chasing down a "front shimmy" issue between 60-65kph and when braking at that speed also.
I firstly discovered the idler arm bush was shot so replaced it with a new brass/bronze bush but the issue with a violent wobble when braking still remained.
So, I spent some time investigating the front disc brakes which looked as if they had never been touched or serviced.
I firstly removed the pads and inserted some 6mm ply in place of the pads. I pressed the brakes and noticed that the caliper pistons were not all working as they should.
I then sent the calipers away to a specialist brake shop for a complete rebuild and had the rotors skimmed at the same time.
When I picked them up they said that 3 of the pistons were total unserviceable so they replaced all 4 pistons etc.
I got everything back and reinstalled everything including new new bearings and seals.
I then torqued the wheel nuts.
Took it for a test drive and it drive great! No wobble or shimmy.
Cheers
Greg |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sun Oct 22, 2023 9:59 am Post subject: Re: Front end shimmy |
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| lateral wrote: |
Hi everyone,
I would just like to add a brief update to me chasing down a "front shimmy" issue between 60-65kph and when braking at that speed also.
I firstly discovered the idler arm bush was shot so replaced it with a new brass/bronze bush but the issue with a violent wobble when braking still remained.
So, I spent some time investigating the front disc brakes which looked as if they had never been touched or serviced.
I firstly removed the pads and inserted some 6mm ply in place of the pads. I pressed the brakes and noticed that the caliper pistons were not all working as they should.
I then sent the calipers away to a specialist brake shop for a complete rebuild and had the rotors skimmed at the same time.
When I picked them up they said that 3 of the pistons were total unserviceable so they replaced all 4 pistons etc.
I got everything back and reinstalled everything including new new bearings and seals.
I then torqued the wheel nuts.
Took it for a test drive and it drive great! No wobble or shimmy.
Cheers
Greg |
Yes! That is the other thing!
So in general, when chasing down the "wobbles" or shimmies in the front end of 411/412 or Super Beetles, there are three categories you need to work through in order....outside to inside.
1. First...always FIRST....with the age of these vehicles, always check the tires for "flat spotting" unless they are new (and even then I suspect some tires) and check the rims for dents or spread.
2. The brakes. Check your wheel bearing adjustment FIRST, then hand rotate the rotor both cold and warmed up. Look for grabbing spots or warpage. If you find any...next check both radial and axial runnout with an indicator (either a scribe in a clamp or a dial indicator) to quantify it.
Squeeze your caliper piston in and then pump them out and recheck.
The object is to make sure you do not have warped rotors or sticking pistons.
3. The rest is pure suspension. There are a handful of items that either alone or combined just a little bit with other little bits....cause the shimmies.
If you have not inspected or cleaned up the first two categories you will have a rough time. Ray |
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lateral
Samba Member
Joined: August 21, 2012
Posts: 45
Location: Sydney Australia
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| Posted: Sun Oct 22, 2023 11:59 am Post subject: Re: Front end shimmy |
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| Thanks Ray |
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lateral
Samba Member
Joined: August 21, 2012
Posts: 45
Location: Sydney Australia
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| Posted: Sun Jan 14, 2024 8:16 pm Post subject: Re: Front end shimmy |
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Hi Guys
I'm back to having a shimmy and will be starting to work my way through the list of probable causes.
I decided to contact SPAX regarding their front dampers and they were good enough to send me the attached photos with dimensions.
I have a 1969 411 with symmetrical upper mounts and I have managed to get a set of NOS symmetrical mounts with the steel bearing inserts.
Can somebody confirm that these will fit my 411?
Cheers
Greg
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Jan 15, 2024 10:51 am Post subject: Re: Front end shimmy |
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| lateral wrote: |
Hi Guys
I'm back to having a shimmy and will be starting to work my way through the list of probable causes.
I decided to contact SPAX regarding their front dampers and they were good enough to send me the attached photos with dimensions.
I have a 1969 411 with symmetrical upper mounts and I have managed to get a set of NOS symmetrical mounts with the steel bearing inserts.
Can somebody confirm that these will fit my 411?
Cheers
Greg
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I have to dig out my measurements. Give me a day. Those look great!
Adjustable?
Ok....a little more diagnosis in the short term.
So, you have the calipers fixed from last time.
You have the idler arm bushing fixed from last time.
You had the rotors turned...which in my experience is not a great thing to do,especially with the 411 which had thinner rotors. They are very prone to warpage when they are getting close to their limit in thickness. If the wobble is very much the same as it was, it could very well be the rotors.
So you have new early steel/friction bearing type strut mounts....not yet installed but ready to go in?
So, what struts are on it right now?
Have you replaced the centerlink? If not it is suspect. About 90% are shot.
Also you need to check the condition of the radius arm centering rings. If they are cracked or missing (about 90% are) that can cause shimmies as well.
Ray |
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lateral
Samba Member
Joined: August 21, 2012
Posts: 45
Location: Sydney Australia
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| Posted: Mon Jan 15, 2024 3:48 pm Post subject: Re: Front end shimmy |
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Hi Ray,
Thanks for replying.
Here's my answers to your questions:
I have to dig out my measurements. Give me a day. Those look great!
Adjustable?
- I do not know if these are adjustable
Ok....a little more diagnosis in the short term.
So, you have the calipers fixed from last time.
Correct
You have the idler arm bushing fixed from last time.
Correct
You had the rotors turned...which in my experience is not a great thing to do,especially with the 411 which had thinner rotors. They are very prone to warpage when they are getting close to their limit in thickness. If the wobble is very much the same as it was, it could very well be the rotors.
I will check the thickness and get back to you.
So you have new early steel/friction bearing type strut mounts....not yet installed but ready to go in?
I have attached a photo of the NOS Top Mounts I have that have the inner bearing.
So, what struts are on it right now?
I'm pretty sure that the struts are original except for the springs which are aftermarket. I am yet to check for leaks as per one of your other posts.
Have you replaced the centerlink? If not it is suspect. About 90% are shot.
I have a NOS Centre Link that I have attached a photo. Can I just install this without doing the "rebuild"? I won't be driving the car regularly.
Also you need to check the condition of the radius arm centering rings. If they are cracked or missing (about 90% are) that can cause shimmies as well.
I have check the radius arm and other connections that utilise rubber and everything is present.
I also have a new Mercedes steering damper that I was going to fit as well.
Cheers
Greg
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Jan 15, 2024 5:21 pm Post subject: Re: Front end shimmy |
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Ah! you have the "middle years" strut bushings. Those are very nice. I hope they have not hardened up much. You may get 50-60k miles before you need to worry about them. Clean out the bearings with fast evaporating carb cleaner, blow them dry and pack with a good synthetic grease.
The centerlink will be just fine if its NOS. You may get 30-50k out of it. When it craps out, just rebuild it it for $25 in parts and a few hours work.
If you still have your old centerlink on your car now...its good money that its part of the issue.
The centering rings....you cannot SEE whether you have them without at least pulling the rear bolt out of each side, removing the dished washer and rear most rubber donut.
The centering rings were little thin, flanged rings that keep the radius arm centered in the eye and prevent vibration and wear. They were made of the wrong material hardness and they either disintegrate to dust because they were never greased...or they fall out and roll away when being worked on and most mechanics never knew they were there.
There are about 3 ways you can easily make this part for pennies. Its really a packing to be made of plastic that is high wear like Delrin or nylon. It does not have to be the grommet shape the factory made it.
AS for whether your shocks are adjustable...I think they are. That black knob in the picture is an adjusting knob. The tops of your strut rods have double hex flanges. The lower one the larger one...is usually for tightening the nut down. The smaller one looks like what you turn to adjust the valving. Ray |
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lateral
Samba Member
Joined: August 21, 2012
Posts: 45
Location: Sydney Australia
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| Posted: Mon Jan 15, 2024 6:16 pm Post subject: Re: Front end shimmy |
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Hi Ray,
Regarding the "middle years" strut bushings, will these just go straight in without any modifications?
Also, regarding checking the centreing rings, can I simply put the car up on the hoist and check?
Do I need to support the bottom of the struts?
Cheers
Greg |
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