lowering a 411/ 412

[sharkskinman]

me and ray have talking and here is the easy small lowering

rear..regular or econoline shocks
metal plates bolted or welded to the bottom shock mount to extend it downward 1-2"s
(mount will be closer to ground)

the front
audi cartridges (ray has to give me the part #)
(rays) 6" rod under cartridge and a 4" extension on the top of the rod)


....for a bit more lowering +1-2"s
an aluminum rod the diameter of the INSIDE of the strut housing
with a bored hole Slightly bigger than strut rod

(mine will be)
BOTTOM--a 4" piece of rod UNDER the cartridge and a 2" piece (with hole) above cartridge (under cap)
with rod going thru(will move cartridge Down IN the housing 2 more inches

on the top a 4" rod (like a shifter extension) (same as ray)
on the top to reach the top of the strut assembly

with JUSt changeing to audi cartridges you get a 1" drop (about)

with the 4" on the bottom and the 2" at the top
you gain another 2"s drop for a total of 3" drop in the front

coupled with the 1-2"s you move the strut in the rear down
and i think that will be Level and lower than you might think



oit will be a bit till i do this
(gotta get her running first)

but i WILL have Pics and stuff

[Bill K.]

Welcome to Shoptalkforums!

Ray has a lot of good info.

Be aware that the ride height is determined by tire size, springs, and the spring mounts. The strut/shock need to be located within the range of spring travel to dampen bump and droop travel relative to the ride height. Using the strut/shock to lower the car with stock springs will result in no droop travel and handling will suffer - you hit a dip in the road and the car goes down instead of the wheel loosing comfort. Or, you take a hard corner and your inside wheels lift loosing traction.

The Audi insert is a good replacement, but it doesn't lower the car with stock springs unless you lower the insert, removing droop travel and compress the spring with the rod at full extension - not recommended. With proper droop travel, the insert rod is free to extended when the wheel goes down and ride height is established by the tires, springs, and mounts.

BMW E30 front springs fit. No known rear replacements (other than custom wound).

[ubercrap]

Seems like if you're going to use E30 BMW 318i springs, it would be a good idea to use the strut inserts from that car as well, no? I have some springs, but will have to go back to the pull-a-part and get some struts to compare everything.

[raygreenwood]

Welcome to Shoptalkforums!

Ray has a lot of good info.

Be aware that the ride height is determined by tire size, springs, and the spring mounts. The strut/shock need to be located within the range of spring travel to dampen bump and droop travel relative to the ride height. Using the strut/shock to lower the car with stock springs will result in no droop travel and handling will suffer - you hit a dip in the road and the car goes down instead of the wheel loosing comfort. Or, you take a hard corner and your inside wheels lift loosing traction.

The Audi insert is a good replacement, but it doesn't lower the car with stock springs unless you lower the insert, removing droop travel and compress the spring with the rod at full extension - not recommended. With proper droop travel, the insert rod is free to extended when the wheel goes down and ride height is established by the tires, springs, and mounts.

BMW E30 front springs fit. No known rear replacements (other than custom wound).

I know what you are saying but lets be a little clearer for the sake of others.

Actually it does lower the front end instantly...without lowering the cartridge in the strut housing. But only 1".
By design...the stub lowers the front end 1"....which if the rear end is in proper shape spring-wise.... sets the front end dead level to the rear and pivots the rear end around the axle while lifting it 1/2 ".
If you are careful on the machining of the stub....very careful...you can lower the front end another full 1". The area of the spring you are compressing is the softly sprung "comfort" zone at the top. Personally...I do not recommend lowering by this method more than 1". You can get almost another full inch of lowering with low profile tires. Between the stiffer spring setting, better valving of the Audi strut, lower profile tires and better bushings...the handling improves about 200%

What this stub does with the Audi strut cartridge (at its current dimensions) is compress the top of the spring 1". This lowers the top spring plate position 1"...which also lowers the strut bushing by 1"....which lowers the body 1".
If you use the stub design I provided unaltered and it did not lower your front end to dead level...then you screwed up on something.

I have made 3 sets of these so far and they work perfectly...every time.

This issue with "droop travel"...is that it does not actually exist on the 411/412. Or should I say it does not droop enough for it to make a difference. With the stock very heavy springs...and the original oil struts....the cartridge stays fully extended at all times. There is only a small amount of actual strut compression from the weight of the car with an empty trunk.

While its relatively correct to say that the top compression area of the stock spring is the soft road control area....there is more of this area with an unloaded trunk than you need. This is why the car is nose high. This is not to say you should cut it off. This is a progressive spring. All of the spring is necessary.
But for sure 1" and at maximum 2"...still leaves at least 3" of soft progression spring before you get into the flatter stiffer load coil area.
All the Audi stub mod does is set the car dead level, give you a much better handling strut cartridge...and one that is easily and cheaply replaceable. Bear in mind that the 411/412 only uses about 6' maximum of its total rod length for stroke.

I do agree that further compression of the spring....is not a great technique for doing lowering other than just taking that spare inch out of the front end. Yes...it can be done....but I also it will make the front end very hard. It might damage the ball joints.
I really do recommend doing the Audi mod first as is...with low profile tires. You would be surprised at how much lower it is. Ray

Ray

[raygreenwood]

Seems like if you're going to use E30 BMW 318i springs, it would be a good idea to use the strut inserts from that car as well, no? I have some springs, but will have to go back to the pull-a-part and get some struts to compare everything.

No. Cartridges are not matched to springs whatsoever. They nothing to do with each other. Shocks struts are matched leverage and weight. Because of the front engine design (lots of weight) there is more mass to slow down in both directions of stroke.
Though you would think that the BMW springs being of basically the same size as the 411 would then not operate with all of that extra engine weight....its because you have not realized that the BMW strut assembly is mounted on very short A-arms closer to the pivot point. The weight exerts much less leverage on the springs because the short control arms. The BMW valving is not even remotely close to what 411/412's require.
I know this for a fact because I have been inside them when I was looking for correct valving.

These are the same reasons why the REAR shock of the 411/412 ...is the exact same part that fits the FRONT end of an econoline 1/2 ton or 3/4 ton van....with a v-8 or v-6 engine . Yes...exact same part...inside and out. You would think that a puny shock like that would get pounded by the Econolines 1000 lbs of engine and frame. But the econoline has stubby little control arms and very heavy springs. The weight exerts very little leverage to move the shocks or springs.
Conversely.....years ago...I put Rancho Rs 9000 adjustables from an F-250 truck on the rear of my 412. I wasted them in a little over a month.....why?....because their valving is actually too light. that truck has massive leaf springs that move the shocks very little. On the 412...the shock sits about 2.5' from the pivot point of the trailing arm. It gets worked very hard.

Ray

[ubercrap]

Ah, I get it! You'll have to bear with me, I'm no engineer. Now I can see why the hunt for substitute dampers amongst existing production vehicles would be arduous...

[raygreenwood]

No sweat! i'm not an engineer either (though I do like taking the train ).....I found out most of this through a lot of trial and error and a lot of reading and asking questions....and swapping parts from wrecks and driving on them.

Dampers or shocks are almost as difficult to size as springs. I took me a while to discover that the springs ARE the suspension. The shocks just arrest velocity from movement and keep the springs from over-extending or over compressing violently. The shocks also arrest small chassis movements to keep oscillation down and keep the tires planted on the pavement.

This is why I tell people that unless you have a lot of time on your hands and are very fast as swapping parts and trying them out.....be very careful when trying to lower or modify suspension. Its not a simple as simply making the car lower.

When you take any spring on a car...it has a designed at rest length. That means that when the car is in its normal state...the spring is compressed to a certain length. It has a certain amount of tension locked up in it at that length already. As you compress it further it increases tension. At some point the tension increases enough to arrest the motion of the body that is compressing it. It will then unload and go back to its at rest state.

If...in the case of a strut....you change that at rest starting point of that spring by making the rod shorter....you add more starting tension into it. The means that the spring will have to compress less...or have less travel...to reach the point where it arrests the weight of the body and begin to return.

Because the stroke of the strut cartridge is now different with that shorter stroke.....the strut cartridge may not have time to build up the correct pressure required in that shortere stroke length to arrest the energy created by the compression and return velocity. In short.....changing the starting spring compression changes the strutc cartridge valve that is required.

Other unintended consequnces are that there are other parts in the chain of motion that are flexible and absorb energy by design. The strut bushing and the spring inside of the ball joint at the bottom of the strut are also in this chain of energy.
If by increasing the starting spring tension you add more energy into the rebound stroke...it can beat up the strut bushings. If by increasing the starting spring tension you already have more compression stroke arresting energy than the valving rate can handle.....it creates excessive compression velocity on the spring. That velocity or energy has to go somewhere. It can commonly be transferred to the spring inside ofthe ball joint causing overcompression and breakage of that spring.

When the damper valving is overly stiffened...to control rough handling and ride by overly tight or overly weak springs....those dampers can wear out very fast. Ray

[Bill K.]

I know what you are saying but lets be a little clearer for the sake of others.

Actually it does lower the front end instantly...without lowering the cartridge in the strut housing. But only 1".

Right on, I'm all for clarity. Help me understand how a shorter strut insert rod lowers the car while still maintaining droop travel...

Here's how I see it using rough numbers...

Say the spring (progressive blue or linear yellow, either way) is 17" free length all alone on the bench. A given load deflects the spring from free length a given amount independant of preload. Assemble the spring into the strut assembly with stock strut insert and say the spring is now 12". Now put the weight of the car on the strut assembly lowering the top spring plate further and the spring is 10" due to the weight of the car compressing the spring from 17" to 10". The difference between preload height (12") and ride height (10") is "droop travel" or 2". Preload only keeps the spring seated at full droop. In this case, preload as affected by insert rod length does not set the ride height, the weight of the car and the spring does.

Now use a different strut insert whereby the full extended length is shortened compared to stock as assembled in the strut tube (for example with a shorter overall rod insert length located at the top of the strut tube) so the preload length is shorten from 12" to 11". Now put the weight of the car on the strut assembly with the same spring and the spring will still compress to 10" but we will have only 1" of droop travel.

Right, the trunk is empty. So fill up with gas and load up the trunk to lower the ride height from 10" to 9" lowering the car 1" and regaining 1" of droop travel. Now the weight of the car has increased, so the car is lower.

In this example, we need to shorten the extended length of the strut insert so the stock spring is preloaded to <10" height to lower the car (with trunk empty) compared to stock. When the preload height is set to a spring load that exceeds the weight of the car, the fully extended strut insert rod length dictates ride height and droop travel is reduced to zero. Load up the trunk to overcome the spring preload to lower the car further and regain some droop travel...

[raygreenwood]

Thats not quite correct. You need to (a) try this modification and (b) measure the compressed spring heights......before coming to this conclusion.

(1) The weight of the body when unladen Will only significantly compress the strut springs from their assembled free unladen length (the length of the spring between top plate and bottom perch when the strut is assembled and out of the car)...when you are using original oil struts.

Otherwise the relatively light front end of the 411/412 does little to depress the coil springs. Over 50% of the weight of the front end is below the strut assemblies and connected to the ground (primarily the steering knuckle castings, brakes and control arms).

(2) When using gas struts, the spring stays almost totally extended all of the time.

(3) the Audi strut...is about 6" shorter than the 411/412 rod. The Stub...only adds a portion of that back. Repeat....the stub is NOT designed in any way or means to make the Audi strut rod ...the same length as the original strut rod.

(4) because you still have a short space of soft coil at the top of the...what weight compression there is (which is virtually nil even on the stock set up...which is why the front end is sitting up in the air).....is virtually the same.

In short...with this mod you end up with a shorter strut rod....which leads to a shorter spring...which leads to the strut mount being 1" lower...which leads to the body sitting 1" lower...even if it does not compress at all.

This mod was designed specifically to lower the front end...even if the strut remains fully extended due to the spring....that means with the weight of the car on it.

It works...100%. I put 86,000 miles on it in my car before I blew the engine (which hopefully will be back in it by August).

You cannot calculate whether this mod will work or not on the workbench. As it was...I made six different stubs to end up setting the proper compression and ride height before I found what worked.
I have been trying to get people to quit trying to "intellectualize" this design for 8 years. I wasn't able to do that either.
My first intellectual calculation of what "should" work for the stub...with a given spring and a gas cartridge of X-valving was not only a failure at setting level ride height...I damn near rolled the car. The 2nd and 3rd iterations lowered the car but destroyed one ball joint each. Costly.
The fourth iteration was stable but a hair nose down and caused oscillations over normal highway features at highway speeds because too much of the "comfort" zone (what you would call the droop area) of the spring was compressed. The fifth worked great. the sixth was an improvement in strength and allowed after market bump stops only.

You can't do this on the workbench. You can't do this with oil struts.....that requires a different stub design/step length because oil struts do compress more from body weight. You can't do this with high pressure gas cartridges....unless you change springs....or it literally destroys both the springs in the ball joints and cracks the centering ring grommets because of leverage.

If you want pictures of the front end of my car...I'll be happy to send them to you. You really need to simply make a set of stubs if you want to really see how this works. Ray

[Bill K.]

It appears we agree.

This mod was designed specifically to lower the front end...even if the strut remains fully extended due to the spring....that means with the weight of the car on it.

Your strut rod extension appears to preload the spring beyond the load applied to the spring from the weight of the car. This effectively lowers the car but eliminates droop travel (so when car is rolled, the inside tire lifts without further rod extension).

My latest build uses the KYB 365008 gas strut inserts (Audi 4000) but without a rod extension. I'm using BMW E30 M3 springs (linear spring rate, shorter height). My results are different than yours. My car compresses the BMW spring and the gas insert 2" when lowered to the ground (empty trunk, spare, tool bag, full tank). My measurements indicate the weight on the front struts is far more than nil (~450lb each).

The suspension has about 2" of droop travel and 3" of bump travel. The front is lowered about 1.5" (adjusted for equal size tires front/back, but shown below with 195-40 front; 205-50 rear). It rides a bit stiffer than before, but handles better. I'm pretty sure both front wheels are still on the ground when I slam it into a corner.



Without further "intellectualization", I hope the original poster understands the effects of raising and lower the rod end of a strut insert or shock without changing the spring.

Shortening the full extension rod length increases spring preload. When spring preload exceeds the weight applied to the spring from the car at rest, the car will be lowered. Lifting the car (drooping the wheel) will lift the wheel from the ground without further rod extension (the rod is already fully extended with weight of car applied). When wheels leave the ground during cornering, steering and traction performance is decreased.

If the rod is at full extension, then as Ray has found it must be precisely set so road dynamics compress the spring when added load is applied. Excessive preload would result in a "dead zone" where when added load is applied, deflection does not occur until the preload is overcome.

To maintain droop travel, the rod must not be at full extension with the weight of the car on the spring. The following changes will lower the car while maintaining droop travel (assuming proper insert/shock stroke and location): shorter spring, lower spring rate, lower bottom perch, or lower strut mount. The amount of adequate droop travel is related to the amount of body roll and the size of "pot-holes" you expect to handle.

Anyway, this is what I've come up with working on (and driving) this for a bit.
Bill

[sharkskinman]

ok...
lowering the cartridge in the strut body
lowers the car by Compressing the spring 1-3"s, right?

wouldnt that make the initial reaction tighter
as you are already in a preload as if there is weight in the front trunk

your using a Shorter spring (E30) and the audi cartridge Without the Extention on the top?
is there anything under the cartridge?
or does the audi cartridge just fit with the E30 springs due to the springs being shorter?

and you say it lowers it how much?

im not looking to race this car
i mean i drive my T3 like i stole it sometimes
but im used to surfing the asphalt around pot holes and Construction plates

do you have any other pics of the wheels and fenderwells and what not
as it sits or (equal tires)
are you running adapters?
those are cayenne wheels
i had a set on my 70 square
i know they are ET53
and with the 1" adapter it puts it down to ET28
i would really like to see how they sit at YOUR height and Tire Size..!!


235/65/17s straight off a cayenne with 4x130-5x130 adapters and 7mm of spacers

[Bill K.]

Sweet looking square with the Cayenne wheels. Truck tires don't work though.

I'll post the details of my "V2" config with M3 coil and Audi insert later. It's similar to the "V1" config shown in this thread.

The Audi insert has a bottom spacer and radial spacers to fit in the 412 strut tube. It only works by using the Mazda spring plate bearing to allow for the short Audi rod end. The stock bump stop is replaced as well.

The spring plate to strut bearing height accounts for some of the lowering effect. The front is currently 1.75" lower than the rear with the 195-40 front/205-50 rear tires as measured from the rocker panel front/rear. The planned "V3" config will raise the front about 0.4" as the spring plate to strut bearing distance of V1 and V2 is too short causing rubbing of the spring plate on the strut bearing housing when an abrupt bump is hit due to flex of the strut mount bushing. More details to follow.

[ubercrap]

Hey Bill K., when you referred to the M3 springs, I'm assuming you meant they are shorter (probably stiffer too) than other E30 BMW springs? Did you previously have 318i springs on there or something else?

[Bill K.]

Yes, V1 has 318i springs and Koni Type 4 adjustable inserts (for sale here - any offers?). V2 has E30 M3 springs with KYB 365008 gas inserts (Audi 4000). E30 M3 springs are shorter and made from slightly thicker wire compared to the standard E30 springs. The E30 M3 springs are what Wally used on his ride, but mistakenly informed us that they are standard E30. The E30 M3 springs have 6 coils while the E30 standard coils have 7 coils.

[raygreenwood]

It appears we agree.

This mod was designed specifically to lower the front end...even if the strut remains fully extended due to the spring....that means with the weight of the car on it.

Your strut rod extension appears to preload the spring beyond the load applied to the spring from the weight of the car. This effectively lowers the car but eliminates droop travel (so when car is rolled, the inside tire lifts without further rod extension).

No we don't agree at all.

What you wrote above.... is an assumption...and an incorrect one. You need to make and try a stub system before you make that type of assumption.

Again.....that is an intellectualization. I don't mean that in a mean way. I do it to. I did it for years playing with this front end.
Your brain calculates that this is what will happen so you ASSUME it will. The inside wheel...NEVER lifts at high speed with this set up....because (a) I have gotten rid of the excess front-end body roll that causes that, with the strut valving, radius arm bushings and spring compression level...because going through hard cornering at high speed...the outer strut no longer over-compresses....dropping the body on the outside edge and causing the inside strut cartridge to max out against the length of the rod..... and (b) ...as I have mentioned numerous... numerous times...you cannot affect this mod (and probably yours as well) without upgrading the rear suspension to the double sway bar....or at least some calculated combo of stiffer sway or spring control.
The body roll that causes the lift you are speculating about .....which never happens even on high speed hairpins.....would happen because of a combination of the front outer diving (which I mentioned previously I no longer have)...and the inner rear wheel lifting due to inertia and the inadequate rear sway control and jacking of the inner wheel.

This car handles flat as a board. But what can and will cause difficulties with the stub system...is if you end up using tires of stock sidewall profile. You do not need super low (like 45's)...but a 5-60 series will do fine. Excessive side wall height creates excessive scrubbing and roll characteristic.

My latest build uses the KYB 365008 gas strut inserts (Audi 4000) but without a rod extension. I'm using BMW E30 M3 springs (linear spring rate, shorter height). My results are different than yours. My car compresses the BMW spring and the gas insert 2" when lowered to the ground (empty trunk, spare, tool bag, full tank). My measurements indicate the weight on the front struts is far more than nil (~450lb each).

Interesting...so you have found the same as I did that the valving of this strut series is pretty decent for the shape, weight and inertia of the vehicle. Interesting spring characteristics.

The suspension has about 2" of droop travel and 3" of bump travel. The front is lowered about 1.5" (adjusted for equal size tires front/back, but shown below with 195-40 front; 205-50 rear). It rides a bit stiffer than before, but handles better. I'm pretty sure both front wheels are still on the ground when I slam it into a corner.

similar result...simply a different combo. I'm 100% positive my wheels are on the ground when I corner at high speeds....and I've had it on the track to play with it.....plus over 80,000 miles of travel. This was not a simple slap it together modification. I spent years working on this.....and driving and testing it.



Without further "intellectualization", I hope the original poster understands the effects of raising and lower the rod end of a strut insert or shock without changing the spring.

Not necessary within certain specific limits...and I mean specific. This is a specific ombination just like yours

Shortening the full extension rod length increases spring preload. When spring preload exceeds the weight applied to the spring from the car at rest, the car will be lowered. Lifting the car (drooping the wheel) will lift the wheel from the ground without further rod extension (the rod is already fully extended with weight of car applied). When wheels leave the ground during cornering, steering and traction performance is decreased.

Again...you have made an assumption that this happens.... which is does not. Do the mod and try it before you tell someone what it does and does not do.

If the rod is at full extension, then as Ray has found it must be precisely set so road dynamics compress the spring when added load is applied. Excessive preload would result in a "dead zone" where when added load is applied, deflection does not occur until the preload is overcome.

Incorrect. You have not tested and do not understand the progressive nature of the stock spring in this combination...with the valving at hand...with this particular gas pressure, and with the other mods to the suspension.

If you will carefully notice....I specify which shock type and brand. What mods to use in all areas of the front and rear suspension in order for this to work perfectly....and it works perfectly. Also....this will not work the same if you start playing with the stub length. Again its a specific combo

To maintain droop travel, the rod must not be at full extension with the weight of the car on the spring. The following changes will lower the car while maintaining droop travel (assuming proper insert/shock stroke and location): shorter spring, lower spring rate, lower bottom perch, or lower strut mount. The amount of adequate droop travel is related to the amount of body roll and the size of "pot-holes" you expect to handle.

Anyway, this is what I've come up with working on (and driving) this for a bit.
Bill

I like the work you have done. Great work! Different combo. Our cars actually look nearly identical in ride height/body attitude...save for the lower profile tire you are using compared to mine.

But bear this in mind...you are 100% incorrect about the assumed handling issues that the modification I made...causes. 100% incorrect.
Bear in mind...I'm not here to sell anything at all. I have nothing for sale and have no intention to.
I greatly appreciate critique. I also appreciate when someone tries the same mod and discovers a suggestion that will help ME make my car even better.

What I don't appreciate is theoretical critique of something you have not tried at all. If you have not done the EXACT combo I outlined (not some variation of it).....I think its kind of off-base to tell people it does not work...when you have no knowledge of it at all.....just assumptions.

You will notice....that I would not attempt a critique of your suspension set-up...without trying it myself.
I think its a disservice to others restoring 411/412's....to tell them that an option they might use...does not work...when you have no knowledge otherwise. I am glad and impressed that you have another totally different option for 411/412 owners. we have so few...every option is welcome. Ray