Suspension Upgrade Options for the M3

Maseroche wrote

Honestly, if you don't track your car then you don't have to worry that much. I'd have gone the Eibach route, if I wanted to install just springs, just because prior experience with them was great.

JAJ wrote

OK, so it's four months or so later and it's time for an update ...

GOVCO wrote

Awesome information in this thread. I think, for my driving style, that I will be going the route of Dinan Stage 2. It may be a little on the higher end, but I feel it yields the best results for what I am looking for.

dcgolfdr wrote

Get the camber plates installed at the same time to cut down on labor costs down the road!!

robbiedawg wrote

if you were looking for a ride that was no harsher than stock,but wanted a little less floatiness on high speed sweepers,what shock/struts would you guys go with?

robbiedawg wrote

what got me thinking about shocks only was this bilstein set from turner-
http://www.turnermotorsport.com/p-2166-e90e92e93-m3-bilstein-heavy-duty-shocks-set-of-4-for-2008-wo-edc.aspx

i just got the car,so i'm in the learning stage

JAJ wrote

Essentially, I couldn't find a string of data points (in an hour or more of data) that would behave sensibly for more than a second or so. You're double integrating, so the process is to integrate from acceleration to velocity, detrend it, then integrate velocity to position and detrend it again. If you pick your start and end points when you can be confident that the suspension is at static height, then you can look at movements away from that static height. You can also look at motion from a "sensibility" perspective to see whether the data says the suspension is in places that physically it just can't go.

For sets longer than a second, you don't get consistent trends for detrending. The accelerometer signal has (what I presume is) low frequency noise components that make the integrated result wander around by 10's of cm over a few seconds.



I did a force vs velocity curve for the OEM dampers based on the acceleration data. F=MA, sprung and unsprung masses and known spring rates allow you to compute the forces and velocities of the suspension parts and graph the contribution from the dampers. This is actually easier to do because you only integrate once, and you can get enough samples to see the shape through the noise. It was an interesting exercise, but I can't find the data on my laptop, and I may have chucked it in a fit of cleaning up.

I thought a lot about analog accelerometers because I'm an analog circuits guy from decades ago. That would have been vastly easier for me to set up and calibrate than digital processing, but vastly harder to post process. I'd have been able to bandpass filter it, integrate and detrend it and get meaningful numbers without breaking a sweat. Digitally, it's not so easy for me. If I was starting now, though, I'd take a close look at Bosch BMA180 digital accelerometers - they have built-in bandpass filtering and data cleanup. They might work better.

BigMacSmallFries wrote

Dude, I'm impressed. Thanks for putting this altogether, and for the others pitching in. Glad I have a working knowledge of our suspension set up.

So, what I'm gathering for those keeping their cars on the street and wanting to keep the costs low is that the Dinan springs with the shortened bump stops are the only way to go (from the lowering spring choices). Track use really requires stepping up to the Coilovers.

..I imagine for those of us tracking only a few times per year, the Dinan would be acceptable for the occasion. Any comments?

JAJ wrote

For those of you following this thread, ponder this:




The context is that I ran the car at a modest speed over a speed bump. As you can see, the wheel (red line) ran over it, the body (green line) followed with a time delay, and the suspension (blue line) ran out of travel twice on compression at about 3cm upward travel with a 5cm extension in between.

leo95se wrote

seeing this, i dont see how sleeve kits could benefit this/a car. We would be adding greater harmonics due to a higher spring rate coupled with stock (lower rate) dampers. it would seem to me, in a non-empirical approach, that this combo would create bounce. also, i dont know if the damper would be able to maintain the same comp/rebound as the spring, which could lead to larger issues.

any view on sleeve kits?

adc wrote

Isn't the EDC damper adjustable? Even self-adjustable in certain modes?

leo95se wrote

yes but the dampers are rated for 120(150?)lb springs. how can compression and bump compensate for a spring rate thats 400+lbs higher?

leo95se wrote

yes but the dampers are rated for 120(150?)lb springs. how can compression and bump compensate for a spring rate thats 400+lbs higher?