My observation on lowering springs.

[fabianyee]

As I've mentioned before somewhere that I replaced my Bilstein Black with Titan tuned front absorbers and found that the front sits lower than before and the Eibach springs were almost fully compressed. It tends to be a bit 'crashy' as going over undulation at speed would fully compress the springs and cause a thud. After few weeks of careful driving over rough roads, I decided to fit back the Bilsteins. From what I measured, observed, checked, bla bla bla. I find that the fault is not the Titan absorbers, it's the eibach springs. it's too soft. With the Titan absorber off the car, I pressed the strut to feel the bound and rebound rate for both the Titan and Bilstein. I found that the Titan is a lot stiffer than the Bilstein. But why is the front sitting lower than the Bilstein and 'crashy'? That is because of the bumpstop/dampener... To verify that, I fit back the bilsteins with the bumpstop in place and lowered te car back on the ground. The front is sitting higher with good clearance gap between the spring coils. But when I tried to move the bumpstop using a screwdriver, it doesn't move. The front is resting on the bumpstop when it's lowered, especially with the Eibachs. That shows that the bumpstop is actually acting as spring.That's my observation. What does that all mean? Think about it. Is it good? No good? Wat's better? Maybe u can tell me more....

 

[kevster30]

Bro,

Good info! Looks like it's time to go for them Bilstein Sports!

*Psssst*.....I think you drive your car too hard ler......*cabut*

 

[fabianyee]

That height is what it was when the springs got in. Meaning all these while it's been resting on the bumpstop.

As for Bilstein Sport, the high pressure may be wat's lifting it up, helping the softer springs to do it 'uplifting' work.

The Bilstein Sport shud have bumpstop too but it's internal as it's inverted tube design like the TITAN. The internal bumpstop shud be at the bottom of the strut.

 

[teejay]

Originally posted by kevster30@Dec 7 2005, 07:41 PM
Bro,

Good info! Looks like it's time to go for them Bilstein Sports!

*Psssst*.....I think you drive your car too hard ler......*cabut*

Bilstein sport absorber spokesman, wonder where you got yours !!!!!!!


Fabs,

this matter alittle more complicated to type, but will try and add my observations and thoughts
i believe the bilstein sports had 2 parts of dampening system, since its progressive, first part would be the springs as the bump stop- is firm and doesn't travel much on soft to medium rebounds, mostly soft easy cruising driving will make the car suspension really comfy, do take a ride in kevsters car

second dampening process is the further compression of the springs by stronger forces- both vertical and horizontal, e,g taking a corner at high speed, or sudden changes in road contours at high speed
this sudden hard force compresses the springs to a limit and is then added to the bumpstop which compresses much more this time

notice there are 2 types of dampening, first the bump stop then the springs, which both have different rates
the absorbers are design to work in conjunction with the dampening rates, so in turn it will act progressively due to the different dampening rates, and int turn have a progressive rebound rate

e.g. ask kevster to drive really slow about 50-60 kmph, how does it feel
then ask him to drive the at the same stretch at 130 kmph, how does that feel? first situation, really comfy, second you can practically feel the car jerking and twitching to every reaction , due to the road, or driver handling
this in turn is progressive,

the bump stop does not rebound to the absorbers, this rate is matched against the spring dampening rates, so this is when you feel the car really comfy and soft

again ,look at kevster smile everytime you ask him if he is satisfied wif his suspension setup.......

to sum up, this is really a unique system, and in a system all parameters are matched within one another, so if the bump stop is there in the first place do you use it, if not you could alter other parameters to make the system back in a balanced state

 

[kevster30]

Teejay,......yes sifu, many thanks for the Bilsteins.....!

 

[Jules]

resting on bumpstop? ( when stationary? )

In my limited experience with BMW, That's NOT NORMAL and means your springs are gone.......

Bumpstop is now RESTSTOP.....

Time to change to new springs and putting sports absorbers help prolong such premature fatigue-ing of your springs.....by reducing the oscillations of cold working.

 

[fabianyee]

Originally posted by Jules@Dec 8 2005, 09:36 AM
resting on bumpstop? ( when stationary? )

In my limited experience with BMW, That's NOT NORMAL and means your springs are gone.......

Bumpstop is now RESTSTOP.....

Time to change to new springs and putting sports absorbers help prolong such premature fatigue-ing of your springs.....by reducing the oscillations of cold working.

Springs are not gone. u can do a survey and check with most E30 with eibach and find the same result.

Eibach prokit springs are soft hence the comfort

 

[elwine30]

so, it's good or no good ?

 

[ALBundy]

My observation...springs have to be matched with the absorbers. IN your case...to say its not matching is an understatement The ride height is more or less determined by the spring and not the absorber..and something is defintely wrong with the Titan, either wrongly design or its faulty

 

[kevster30]

Fabs,

What is your opinion on these findings? I am sure that it will satisfy many curious readers here.

Obviously, as Jules has stated clearly, resting on bumpstops is definately not the norm. However, the Eibach pro-kit is designed to be used with the OEM absorbers.

So how? What was the ride and handling like on:

1) Blistein and Eibach combo
2) Titan and Eibach combo
3) Titan on titan combo

BTW, could this situation exist becos of your W124 absorbers in the rear? perhaps the are pushing the front end of the car down? I oso dunno.....just wondering.....

Maybe you could try the Titan springs with the Bilstein absorbers next.

 

[Alvin]

Just go with ground control fast road kit with Bilsteins. No worries. Ride is not too harsh & handling is superb!

But i think the titan's are too hard which will actually be bad for the handling. Best would be the bilstein & Eibach combo if you have comfort in mind. You can ask Tom bout the Titan kit with the coil overs. I tried & its feels harsher than my GC Auto-X/Track rated coilovers!

But then again its just my feel. whatever work dude!

 

[fabianyee]

Originally posted by ALBundy@Dec 8 2005, 11:54 AM
My observation...springs have to be matched with the absorbers. IN your case...to say its not matching is an understatement The ride height is more or less determined by the spring and not the absorber..and something is defintely wrong with the Titan, either wrongly design or its faulty

Problem is not with the Titan. the Eibach springs is soft...

Read the first post again...

Like u said, ride height is determined by the spring rate not the absorbers.

With Eibach Springs+Bilstein Black+bumpstop, ride height was as per first day with the Eibach springs installed (2 years ago). But bear in mind that also mean that the car has been resting on the bumpstop since the start.

With Eibach Springs+Titan (no bumpstop), ride height was lower and springs almost fully compressed.

And Titan's damping rate is actually a lot stiffer than the Bilstein. But the difference in both set up is the BUMPSTOP.

Conclusion: Eibach springs HAS to depend on the bumpstop. at least that's the case for OEM absorbers. Without the bumpstop, I foresee the front end would be more crashy and sits lower.
Can't comment though for the Bilstein Sports.. since I haven't played with it.

The Titan springs is a whole lot stiffer but they're on another car aledi. But it's not the coilover springs. It's actually coil springs from another BMW. Need to check with Tom what springs he gave Titan to fit on.

 

[ALBundy]

Oh forgot about the bump stop being removed

Mr. Moderator (where art thou?)!! I think this thread is at the wrong section!

 

[fabianyee]

Originally posted by ALBundy@Dec 9 2005, 03:59 PM
Oh forgot about the bump stop being removed

Mr. Moderator (where art thou?)!! I think this thread is at the wrong section!

oops. didn't notice it's started under Classifieds' 'Chassis and Wheels'.. Have been towed to BMW Tech and Performance's 'Chassis and Wheels Tech'

 

[The Necessary]

That is very odd, Fabian, because the ride height of a vehicle is supposed to be dictated by the springs, and not the shocks...

You say the Titan absorbers are stiffer, that could be due to them having a much more limited "travel", but even so, the springs should be able to hold the weight of the car up without assistance from the dampers/shockers (different direction of force anyways?).

Strange, very, very, strange...

 

[scin]

Does this help?

 

[fabianyee]

Originally posted by The Necessary@Dec 9 2005, 04:45 PM
That is very odd, Fabian, because the ride height of a vehicle is supposed to be dictated by the springs, and not the shocks...

You say the Titan absorbers are stiffer, that could be due to them having a much more limited "travel", but even so, the springs should be able to hold the weight of the car up without assistance from the dampers/shockers (different direction of force anyways?).

Strange, very, very, strange...

That's why I say the bumpstop is the determining factor. The Eibach springs are soft and actually needed the bumpstop to part of its job. so the front is actually resting on bumpstop.

That's probably why the Eibach springs gives u the 'progressive' feel. The stiffer feel was actually provided by the bumpstop.

With the Titan absorbers, I can put the bumpstop bcos of the inverted tube design (like the Bilstein Sport - thick strut shaft).

 

[teejay]

fabs,

i think you answered your own question.........

scin,
great feedback on the design

however, i feel the bump stop did make part of the suspension setup tuned with the eibach, but remember how the coils of the eibach are coiled further apart in the center, making them "soft" this is where the bumpstop-bmw calls it damper- does part of the dampening and rebound, if forces are hard enough, it overcomes the bumpstop properties and works against the springs

 

[fabianyee]

Originally posted by teejay@Dec 9 2005, 05:18 PM
fabs,

i think you answered your own question.........

I actually knew it all along.

Just wanna throw out a question to get everyone to think about it. Most people here tend to just follow trend and don't know technically what they are getting.

 

[The Necessary]

But, Fabian, if the springs cannot take the weight of the car, regardless of what shocker/damper you are using, something must be desperately wrong leh...? You sure it's a 4 cylinder engine you have up front ah?