Lets be clear about Lowering and BMW E30 Springs thread

[tim3]

Ok so I finally got a 412. 1974 4-door. I read through all the lowering techniques. Yes I know the issues.. its clear but what isnt clear is how much drop the regular BMW E30 springs vs the BMW E30 M3 springs drop front of the car. I can find regular BMW E30 springs on ebay but the only M3 versions I can find are aftermarket and lower an E30 M3 an additional 0.25".. i would appreciate a clear answer on my question not some long winded explanation that doesnt answer my question. Ive searched high and low for the difference in drop height and how much of an overall drop BMW E30 springs achieve but all Im finding is vague info that devolves into a discussion about all the stupid issues these cars have. I get it.. but im here to get a clear answer about this question and yes I'll also do all the other stuff with the struts/bushings/ect. But please can someone just tell me how much E30 and E30 M3 springs drop the car (not just it levels it or tangets about spring rates, strut rebound, hitting bumps, bushings, strut bearings, audi struts, or w/e stuff that doesnt answer this question above)
Thanks in advance

_________________
Click to view image

[raygreenwood]

Sigh.....

You want a simple and quick answer?...not one person on this planet knows.

Springs have very little to do with ride height in a MacPherson strut unit. In fact....they have virtually nothing to do with it.

All of that stuff that you have no interest in....makes all the difference. Shorter springs simply FIT the RANGE differences you make with the bushings, spacers and strut rod.

These rules apply for super beetle and type 4 only.....simply because we have very little weight in the front end.

Struts will extend to the telescopic range of the strut rod when the wheels are just lifted off the ground. That is your max limit. Then....you will get a SMALL amount of combined rod and spring compression when the wheels are back on the ground and the weight of the vehicle is on it.

You want to lower this at rest height some more?....well....put softer springs on it and it will droop lower at rest.

So why can't you just do that witha shorter spring instead of a softer one?.....because if the spring is just a smidgen too short....and you go over a bump where the wheel leaves the ground....the strut rod extends fully....and the spring comes unseated and drops sideways. If you are lucky it just bends the lower spring perch. If you are turning when this happens....it gets hooked on the center and bends the fender.....been there and done that. It's how I know.

Strut springs for a street car need to be progressive. Soft area for compression for setting height....and heavier springs in the lower section for load control.

If you want to use some other spring...either stiffer or softer....that's fine but your main work is going to be adjusting the extended rod height to get the maximum range FIRST....and then testing your springs to get the kind of at rest stance you want along with proper compression and rebound action (a chunk of that is also valving).

It's not simple and it's not about just slamming in a set of "lowering springs". This is neither torsion bar or trailing wishbone suspension where you can get away with that.

However, the rear suspension is like that. You can use some lowering springs in the back and get an immediate result. However, you still have to be sure that your shock total extended length is not now too long because if you drive over a huge bump and the tire leaves the ground you can unseat the spring.

How much drop for BMW E30 springs? Who knows. No one does because its not JUST the springs that allow or cause the drop.
There is maybe one guy who could tell you from about 6-7 year back (Greg?)....and I can tell you from following what he did.....it's the whole combination and not just the springs.

For the most part you can get ~1.5" drop just with the stock springs (which are excellent by the way)...simply by installing the Audi cartridge mod and adjusting your bump stop spacers. This is also about 200% better handling with this combo.

Visually, on the front end a 412....the appearance of a 1.0" drop looks very much like 2.0"+...because it lifts the rear, pivoting around the rear axle and causes the control arms to "squat". This brings the fender wells past the lip of the tire and the rail edge of the rocker panel down past parallel with the ground (slightly) towards the front.

There is no simple method for lowering a 412. While the actual work is very easy.....it's a lot of trial and error....and....4 out of 5 things you try can either make for poor handling and ride or actually damage something at the extremes (like your ball joints).

Nice looking car! If someone tells you they have a simple or concise answer as to how much ANY set of springs will drop your car.....and you have not told them the rest of the combo....or they have not dictated the whole combo along with said springs.....they are full of shit.

Ray

[tim3]

This group kinda sucks. Its been nearly 20 years and not one of you can give an estimate how much a stock e30 spring will drop the front of the car vs a e30 m3 spring.. guess this is why no one really gives a shit about type 4s because the forum is full of the same fear mongering bullshit over and over again for 20 years.. we get it the suspension fucking sucks. I asked a simple question.. thanks for writing a fucking bible like you have for the past two decades.
_________________
Click to view image

[raygreenwood]

[raygreenwood]

Just so you understand that I am not being a complete asshole….here is some data for you.

https://www.thesamba.com/vw/forum/viewtopic.php?t=764509 For reference, this is my thread on rebuilding struts specifically for the 1974 model 412 using the Audi cartridge mod

This lowering thread below is a good one and also has Bill K’s input. He was who I was thinking of when I said "Greg" in my last response.

He has done the BMW spring mod on his 411 and 412 IIRC and used to sell kits for it but that was in 2010.
Also contact Wally on the STF. His highly modified 412 has modified and lowered suspension. This was years ago. I know he is still on there but do not know if he still has his 411.
https://www.thesamba.com/vw/forum/viewtopic.php?p=7437142

The point I am going to make…again….is when these guys tell you how much the EXACT spring they used lowered their car….do yourself a favor and ask them what the TOTAL RECIPE is. What spring, what mount, what strut cartridge, brand and series, what spacing length for that cartridge, what spacers and shims are in the stack up….all of it…..because just knowing and using the springs will get you nowhere.

You will see this from the data in the links below.

Below is data from this BMW thread:

https://www.rtsauto.com/e30-stock-spring-options-and-spring-rates/

Looking at the BMW E30 data you will SEE why just getting the springs, no one can give you the simple answer you want.

First, WHICH BMW E30 spring are you using?
There are at least 4 with unloaded spring heights from 345mm to 305.7mm and each one of these has differing spring tension at normal full extension and at maximum complete, coil bind compression (which you would never do while driving).

So….while the Tallest BMW spring of 345mm is 40mm shorter than the 385mm of the shortest 411 spring, they are both tall enough to capture the stock upper and lower spring perches which are 282.6mm apart.
See the point I am making?

Just being 40mm shorter than the shortest stock 411 spring with the S704 M series spring, or even 80mm shorter than the shortest stock 411 spring ….if you are looking at the E30 M3 Evo-3 which is 305mm fully extended….both of those BMW springs will load into that 282.6mm of space on the standard 411/412 strut between the top plate and lower perch.

Without knowing how much difference in spring force each spring will have at that 282.6mm loaded height, you have no idea how much the weight of the car will compress that spring when just sitting…IF it compresses the spring at all.


How heavy is your car?
How much weight is commonly going to be in the trunk?
Are you using oil strut cartridges, low pressure gas or high pressure gas catridges?


The only way anyone can know how much any given BMW E30 spring will lower their 411/412 with no other changes to the strut at all….is to try them on and test .

Then, if you want to have actual operating struts… since new strut cartridges are unobtanium….you need to graft in another strut cartridge like we have done.
When you do that, it could have (or require) either the stock spacing in length between top plate and lower perch or you could lower or even raise the car while installing this new strut cartridge.

So, here is the data from that thread so you don’t have to click if you do not want to:

Front Springs:

S704 M sport suspension package (pre 09/87) 31331132742 with Pink dots:
Spring force = 3514 – 3686 Newton at Ln length 140 mm
Spring rate at upper/extended level: 26.328 N/mm or 150.336 lb per inch

M-tech suspension package (09/87+) 31331130054:
Spring force = 3426 – 3614 Newton at Ln length 126.5 mm
Spring rate at upper/extended level: 28.569 N/mm or 163.133 lb per inch

E30 M3 springs 31331130046:
Spring force = 3117-3283 Newton at Ln length 126.5 mm
Spring rate at upper/extended level: 25.952 N/mm or 148.189 lb per inch

E30 M3 Evo 3 springs 31332226781:
Spring force = 2970-3130 Newton at Ln length 116.5 mm
Spring rate at upper/extended level: 26.875 N/mm or 153.46 lb per inch

Overall heights in order (S704 not available, albeit overall longest of the 4):
NOTE: from a different source, BMW E30 for S704 “should be” 345mm

31332226781 (E30 M3 Evo 3)> Ln: 116.5 mm / Overall: 305.7 mm
31331130054 (Mtech) > Ln: 126.5 mm / Overall: 313 mm
31331130046 (E30 M3) Ln: 126.5 mm / Overall: 318 mm

Spring Rates in order- lowest to highest:
31331130046 (E30 M3) > 148.189 lb per inch
31331132742 (S704 M package) > 150.336 lb per inch
31332226781 (E30 M3 Evo 3)> 153.46 lb per inch
31331130054 (Mtech) > 163.133 lb per inch

The BMW spring mod is a good one. But most people who do not want to really lower any lower than flat and level….have no used it and probably do not need it. Its why you do not see much about it.

Just for a recap to what I have done....wth stock springs:

With some recent changes to my front mounts I have lowering.... of 1.25” using the Audi strut mod and an adapter bushing. I have a further 26mm of lowering just by having 205/55 -15’s on the car instead of the stock 185/75 tires that it had when I bought it.

That’s 2.25” of lowering using the stock spring plate spacing ( minus 1.25”) and low pressure gas struts with an adjusted adapter stub. It also has probably 15%-ish greater at rest spring load.

At this point I do not need to do anything to the rear end yet. Its barely noticeable that the front is slightly lower than the rear….but the front is significantly lower than a stock car.

With finally finding an answer for a NEW balljoint that these cars can use (yes, it takes a little fabricating...the how to is coming soon!)….this could easily bring an extra 0.75” drop in the blink of an eye if I want it. This would leave the front at 3” lower than stock.

At that point I will have to adjust the lower eye position on the rear shock by ¾”.
All of this…3” of lowering….without BMW springs.
And I have not even mentioned the Volvo spring mods that are out there. They are all worthwhile mods if done well.

But you are either going to have to buy a complete answer...meaning a finished "RECIPE" from someone like Bill K...or you will have to just buy some springs and start testing like I have done...Bill has done and Wally and others have done.
Just sayin….

Ray

[412STi]

As Ray has already written,
there is no information or records for the many decades.

Someone who has lowered their car with BMW springs may have posted a photo somewhere at some point.
Unfortunately, I don't have a photo of mine.

It's been over 30 years since I did the conversion and the car has been dismantled for almost as long and has been in the process of being rebuilt for a few years.

What I can contribute is the following:

I installed springs from the E30 4-cylinder and my shock absorbers were shortened custom-made ones from Koni.

If you want to do this conversion, you should definitely only use the original 4-cylinder springs (316/318).
They work even if the rest is still original (old shock absorbers, etc.), without losing the preload when fully extended. (Better and safer with adapted dampers, though)
You shouldn't use the springs from the 6-cylinder, as they are designed for a heavier engine. And we don't have one in the front.
What I would also definitely not use are M3 or other sports suspension springs. These are even shorter than the original 4 cylinder springs and therefore have no preload at all.

No guarantee that all of this is still correct. I wrote it down more from memory.

Found some pictures on my PC

with BMW E30

with BMW E30

with E30 6Zyl.-Spring and Bilstein

E30 Spring

E30 Spring

@Ray
Wally sold his sedan to a Dutch friend (Joost) years ago.
_________________
Gerold
The morning brings a mystery, the evening makes it history

The oil can not be, was none in it.

[raygreenwood]