Just a quick question for you gearheads. I am thinking of putting some shorter "sport" shocks on my BMW 323i. I don't have a sporty shock system, so I was wondering if there are any dangerous effects of using sport springs with the softer, stock shocks. Thanks!

Underdamping could definitely be an issue... and possibly the new springs are too short for the new shocks. A quick search produced this:

Quote :

A too long a shock absorber would cause the piston to hit against the bottom of the shock absorber during its downward stroke or doing a sharp cornering or braking. Too long or too short a shock absorber would not only constitute to an un-comfortable and un-safe ride it would also damage the shock absorber itself in a very short period of time.

It's not from a reliable source though.

Uhm, Don't do it... If you can't replace the shocks/struts at the same time with better ones and better springs then it will ride like ass.. Ask me how I know.

i have seen bmw's in my shop with only lowering springs,no shocks.. U can do it,but be carfully when driving,or get a full system like i have for my M3,even bilstein or H&R, try at JMK bmw or websites,like turner motorsport,racing dynamics(i usually order from them)

Thanks for the info, all of you. I did some reading, and the springs I have my eye on don't slam your ride. They have a sport version (slightly lower) and a race version (slammed, which they specifically recommend getting new shocks for). I'm looking at the sports, and you'll maybe get somehwere around a .75 inch drop. I'm thinking this should be alright with stock shocks

A .75 - 1.5 inch drop is more than it seems, especially when it's dealing with your suspension. Either way, just be careful. Some mistakes you can't take back

Quote from Slopi :

A .75 - 1.5 inch drop is more than it seems, especially when it's dealing with your suspension. Either way, just be careful. Some mistakes you can't take back

I hear you. There's also a BMW forum I frequent, and someone on it has the race springs installed with the OEM shocks with (apparently) no problem.

From what I understand, I wouldn't recommend it. If you can, wait and buy shocks and springs at the same time. I am sure you would have a better ride and experience that way.

First phase, learn and understand this:
http://e46m3performance.com/tech/transfer/index.htm

Quote from JTbo :

First phase, learn and understand this:
http://e46m3performance.com/tech/transfer/index.htm

I already knew this. Thanks folks!

Quote from TaiFong :

I already knew this. Thanks folks!

Very good

Also don't use Monroe Sensatracks, those seem to self destruct if used on lowered suspension

I have bilstein pss9 on my m3,it drops -1.0,-1.75 and its not that very expensive,~1500 $
here is a pic(found only this 1) : http://img164.imageshack.us/img164/2928/picture120bl4.jpg i can go even more lower but its already too low
I love it

Quote from e2mustang :

I have bilstein pss9 on my m3,it drops -1.0,-1.75 and its not that very expensive,~1500 $
here is a pic(found only this 1) : http://img164.imageshack.us/img164/2928/picture120bl4.jpg i can go even more lower but its already too low
I love it

That's pretty much slammed! Looks nice.

My advice is, if you really want grip, handling and safety, DON'T use lower and stiffer springs with OEM dampers. A potentially deadly combination that if you happen to be to excite it enough, would cause very uncontrolled oscillations with great potential to get you out of control. This assumes the average case whereby the OEM dampers are significantly worn.

In practice, with BMWs, that depends on the condition of your OEM dampers. If they are still nice and taut, they can cope pretty well with normal driving since European cars tend to be tuned with good rebound damping (in general). Don't bother trying to test its absolute limits though. Controllability issues crop up in severe transient conditions such as slalom courses, autocross, or even on road collision evasion. In short you end up paying more money to get LESS overall performance. If you are lucky (or unlucky depending on your point of view) enough to hit regular sequences of bumps at the "correct" speed to excite the system at its natural frequency, the significantly underdamped system could oscillate out of control and the car bounce uncontrollably. All this depends on the actual rate of the lowered springs too though.

As e2mustang said, the Bilstein PSS9 system is ideal for you if you want a lowered car with significantly improved cornering performance. Another path involves the use of Eibach progressive lowering springs and Koni Sport dampers which have very adjustable rebound (stiffest can be up to twice as stiff as softest setting). Or you can check www.koni.com and look for an FSD suspension package.

F - Frequency
S - Selective
D - Damping

Basically a damper that softens itself if the frequency of motion is high enough to reach or exceed a preset threshold. This allows excellent handling since cornering involves relatively lower frequency motions whilst allowing excellent bump compliance, improving both comfort and grip on less than flat surfaces.

Agree with Jamexing