Why Lowering Springs May Ruin Your M3

[808MGuy]

Originally Posted by adc

Well, both the M3 "Edition" package and the upcoming ZCP have a 10mm drop in ride height - and are available with EDC.

Last time I checked, 10mm is only 0.4". That would be inline with Dinan and slightly less than Eibach. I have a feeling that the package does not just include shorter springs though. There's probably more to it to get it to work reliably which is really the most important part of it for the manufacturer.

[Radiation Joe]

Originally Posted by adc

Well, both the M3 "Edition" package and the upcoming ZCP have a 10mm drop in ride height - and are available with EDC.

What he means is that there will be no aftermarket dampers that electronically adjust and are compatible with the EDC electronic controls. There are many spring combinations that can be used with the stock EDC dampers with varying degrees of success.

[xxe92xx]

so if what im reading is correct eibach springs are the safest way to go? all other springs are bullshit? the overall best option would be going with KW straight up...but EDC will be a waste?

currently im only looking for a decent drop, because recently i was stuck just staring at that gap

[Fanta]

I'm trying to see if anybody had any good experience with JRZ Suspension?
If not what would you recommend.
http://www.jrzsuspension.com/index.php?home

[FrenchBoy]

I am sorry to say but the rationale from the OP seems over simplistic.

First, as other have mentioned, most springs - including OEM springs - have progressive rates (i.e. the K value in the spring force equation is not constant over the compression band; Force = k * x, where "x" is the the compression/elongation).

Second, aftermarket springs typically have higher rates along the compression band (determined mostly by coils diameter and geometry) which means that the forces acting against the compression of the spring are higher, which in turns creates the stiffer ride.
If a spring is well engineered, the ultimate force to fully compress the spring so that the shock hits the bump stop is so high that it probably never happens in real life.

And yes, you get less travel, but I am not sure that is detrimental to the handling of the car.

BTW, I have had H&R Sport Springs for over 8 months and many track/autocross days: No complaints. Love the ride and feel.

[shiggy]

Originally Posted by Bluechipper

My Eibach springs have been absolutely spot on.

Mild drop, oem ride quality, edc works perfectly.

Best mod I have done. I wouldn't change a thing.

PHEW!!!!....good to hear man...getting my Eibach's installed this weekend and I was worried about EDC...

[Technic]

Originally Posted by adc

Well, both the M3 "Edition" package and the upcoming ZCP have a 10mm drop in ride height - and are available with EDC.

... and if we know something for sure is that BMW can adjust the EDC to match whatever springs/lowering they want and still give you 50,000 miles warranty on it as they designed the sucker, and that the EDC on those two models is different from the EDC in the "regular" M3.

So we cannot assume anything about that 10mm drop and EDC until the exact details of that EDC/springs are published.

[SUB-ZERO]

Originally Posted by xxe92xx

so if what im reading is correct eibach springs are the safest way to go? all other springs are bullshit? the overall best option would be going with KW straight up...but EDC will be a waste?

currently im only looking for a decent drop, because recently i was stuck just staring at that gap

I think the DINAN springs are the safest route and Eibach coming in second place.

[rzm3]

Originally Posted by FrenchBoy

I am sorry to say but the rationale from the OP seems over simplistic.

First, as other have mentioned, most springs - including OEM springs - have progressive rates (i.e. the K value in the spring force equation is not constant over the compression band; Force = k * x, where "x" is the the compression/elongation).

Second, aftermarket springs typically have higher rates along the compression band (determined mostly by coils diameter and geometry) which means that the forces acting against the compression of the spring are higher, which in turns creates the stiffer ride.
If a spring is well engineered, the ultimate force to fully compress the spring so that the shock hits the bump stop is so high that it probably never happens in real life.

And yes, you get less travel, but I am not sure that is detrimental to the handling of the car.

BTW, I have had H&R Sport Springs for over 8 months and many track/autocross days: No complaints. Love the ride and feel.

I think you are missing something here.

When a spring drops the front ride height by 1", you will be riding on the bump stop! This is a fact...

[MrHarris]

Originally Posted by Technic

... and if we know something for sure is that BMW can adjust the EDC to match whatever springs/lowering they want and still give you 50,000 miles warranty on it as they designed the sucker, and that the EDC on those two models is different from the EDC in the "regular" M3.

So we cannot assume anything about that 10mm drop and EDC until the exact details of that EDC/springs are published.

When you find out the exact details of the EDC/shocks used in the GTS w/ the 10mm drop please make a thread and post!

I'm curious if my Eibach springs are still hurting my shocks or not. Feels great compared to the H&R's..

[Trier Germany]

Originally Posted by MrHarris

When you find out the exact details of the EDC/shocks used in the GTS w/ the 10mm drop please make a thread and post!

I'm curious if my Eibach springs are still hurting my shocks or not. Feels great compared to the H&R's..

If i'm not mistaken the GTS has height adjustable suspension from SACHS

[rzm3]

Yes it does. From my understanding it is very similar to the Sachs Performance kit for the regular 3 series and the ACS Racing suspension kit. Probably 20-click single adjustable with up-side-down technology.

[aajami]

And the GTS drop is closer to 35mm. The 10mm drop is for the 7MA and Edition M3s.

[rzm3]

GTS has a HEIGHT-ADJUSTABLE coilover... There is no such thing as a standard ride height.

[aajami]

Originally Posted by rldzhao

GTS has a HEIGHT-ADJUSTABLE coilover... There is no such thing as a standard ride height.

My mistake. Height adjustable up to 35mm, is what I should have said.

Using caps is fun.

[V1.47fan]

Originally Posted by rldzhao

As many of you know, a few members and I have been doing quite a bit of research/measurements/calculations on the M3 suspension. Here is one finding which I thought should be explicitly expressed for the make benefit of the M3 community.

***

Here is why lowering springs may ruin your M3's ride and handling:
(I will try to explain in the simpliest words possible)

The M3 front suspension has about 5.75" of total suspension travel from fully extended (i.e. on a lift) to fully compressed (let's assume no bump stop for now). About half of the 5.75", or 2.875", is dedicated to compression.

Now, let's take lowering spring brand A for example, which drops the car by 1" in the front. So 2.875"-1"=1.875", which means that you will still have 1.875" of compression travel left, which is ok.

***

Well, guess what, there is a OE bump stop on the front suspension which is about 2.375" long uncompressed, and with a 1" drop, you would already be riding on it.

The bump stop behaves progressively (see sample figure below), meaning the rate increases with more compression. And when this bump stop compresses to about 1" (from 2.375"), its rate shoots up, adding significant stiffness to the total effective spring rate. At this point the bump stop is almost like a hard piece of rubber in comparison to the rest of the system.



Now, we were left with 1.875" of compression travel after the drop. Subtract another 1" due to the bump stop, and one is left with 0.875" of effective compression travel. (yes, it is about the width of a finger)

***

The short compression travel (in this type of set up) does a few things:

1) You will get a very bumpy ride, especially when you go over imperfections, as the suspension is constantly hitting the compression limit.
2) This will constantly overwhelm the OE shocks, which is not designed to operate in such a high variable effective spring rate all the time.
3) Unpredictable handling. More weight is transfered to the wheel that has a stiffer rate. When a lot of weight is transferred to the front outer wheel when you are turning, you get understeer.

Hope this helps. This is not to say that all lowering springs will behave this way, but obviously some should be avoided if you don't want to sacrifice the ride and handling just for the look.

"When a lot of weight is transferred...,you get understeer"

I don't think you're transferring a lot of weight to the front by lowering the front by an inch and the rear by half an inch.

You'll get more negative camber up front(at least an additional -.5 degrees than stock),lower CG,less body roll... this should create less understeer(push) and in some cases cause oversteer(loose) if too much weight is transferred to the front making the rear light a la Mustang (tail happy) which isn't the case here anyway.

[duk]

eibach ftw, am so getting those

[rzm3]

Originally Posted by V1.47fan

"When a lot of weight is transferred...,you get understeer"

I don't think you're transferring a lot of weight to the front by lowering the front by an inch and the rear by half an inch.

You'll get more negative camber up front(at least an additional -.5 degrees than stock),lower CG,less body roll... this should create less understeer(push) and in some cases cause oversteer(loose) if too much weight is transferred to the front making the rear light a la Mustang (tail happy) which isn't the case here anyway.

1. One inch is very significant to suspension behavior when the total compression travel is only three inches. One inch to the center of gravity is quite minute in comparison when the CG is about let's say, 20 inches off the ground?

2. When one talks about weight transfer, it is not just the 'downforce' -- it is also the lateral centrifugal force that is created when your vehicle is turning.

More weight transfer to an axle equals more understeer because more grip is required to 'push in' your car... and vice versa.

Now, what you may be thinking about is the 'downforce' that is created by wings or other aerodynamic features. In this context you are getting the benefit of weight (downforce) but not the penalty (lateral centrifugal force).

3. Less body roll does not equal to less weight transfer. When you have stiffer springs there will obviously be less body roll, but the weight transfer from inner to outer wheels is just as much as before.

[ihyln]

so what can be considered definitive for our cars with EDC? Dinan or Eibach? From what I've been reading Dinan is probably the way to go but the drop isn't as noticeable. I can't really make up my mind on this...

[SlamMan]

Originally Posted by rldzhao

3) Unpredictable handling. More weight is transfered to the wheel that has a stiffer rate. When a lot of weight is transferred to the front outer wheel when you are turning, you get understeer.

This is kind of off the main topic but it's my understanding that a stiffer spring transfers weight away from that corner. Obviously, a lot of other factors go into vehicle dynamics, but springs should cause understeer if the rear spring rates are too soft or the front are too stiff.

[PunjabiM3]

So for those of us with drop springs, any idea on when the stock struts will degrade in quality? Eventually, I will more than likely replace everything with coil-overs, but am wondering how many miles I can get out of the stock struts even if it is just an estimate...

[808MGuy]

Originally Posted by PunjabiM3

So for those of us with drop springs, any idea on when the stock struts will degrade in quality? Eventually, I will more than likely replace everything with coil-overs, but am wondering how many miles I can get out of the stock struts even if it is just an estimate...

Nobody can answer that question with any definitive accuracy since:

1) I'm not aware of anyone who had to replace their EDC shocks yet

2) Lifetime of a wear part is not something that can be calculated with precision because there are so many variables that affect rate of wear.