[vasillalov]

Originally Posted by luckyu

Race cars tend to be 2 Hz, or higher. Road cars tend to be 1.5 Hz or lower. Books say that people find >1.5 Hz uncomfortable.

You can compute corner weight from the wet weight BMWUSA gives, and estimating unsprung weight. See the thread "M3 on 328i" for examples.

Front corner:
wetweight * frontweightdist / 2 - 105

Rear corner:
wetweight * (1 - frontweightdist) / 2 - 135

Excellent info yet again! So with this, all of us who want to improve the track ability of our daily drivers can quantify how much comfort each suspension will provide BEFORE we actually spend the money!

[tscdennab]

Here are some formulas found on Eibach site presenting how to calculate suspension frequency, motion rate, wheel rate.

http://eibach.com/eibach/img/ers-14s...nworksheet.pdf

Thanks to Orb who posted it in a 3 year-old thread on another forum (and my endless forum digging abilities)

Edit: After more research, it seems that the aftermarket coilover manufacturers have different spring rate ratios than BMW because they simply tune the car for different purposes, with different suspension frequencies:

Here is how to calculate the "natural" suspension frequency at home, with a stopwatch (it's patented, so it must be good - however the shocks must be removed)

http://www.smithees-racetech.com.au/...cefactors.html

Here is how to calculate other things like spring rates, etc. based on some car measurements (but it's not free, as far as I read):

http://www.smithees-racetech.com.au/...worksheet.html

[neoduffer]

Originally Posted by tag824

I'm lost with the whole frequency thing. So the higher the frequency the less 'race like' a setup it is? I'm looking at getting the Eibach Pro Street S for my car. It's pretty much dead on with ZSP with exception of the progressive springs up front that go up to 271lbs. I'm a n00b when it comes to suspension. Anyone know what I can expect out of that setup?

I would do the math for the frequency myself if I knew what the corner weight was.

Eibach Pro Street S
Front: 134 - 271 lb/in (Progressive)
Rear: 456 lb/in (Linear)

I ended up making a spreadsheet to crank the frequency numbers. I think I got it working correctly.

Front: 134 lb/in = 1.21 Hz, 271 lb/in = 1.72 Hz
Rear: 456 lb/in = 0.8 Hz
This setup will probably ride very close to stock, comfort-wise.

For comparison:
OE 335 F/R, 145/460, 1.26 Hz/0.80 Hz
M3 F/R, 160/550, 1.32 Hz/0.87 Hz
PSS10 F/R, 385/615, 2.05 Hz/0.92 Hz
400/800 F/R, 400/800, 2.09 Hz/1.05 Hz
tscdennab's idea F/R, 224/616, 1.57 Hz/0.92 Hz

[cleex024]

damn...guess ill be the one bringing this thread back to life lol. im still confused about this whole thing...can someone with some exp chime in on how they felt about either 350f/700r or 400f/800r spring rate setups?

bc racing has 400f/650r setup which seems the stock setup for 335i and im trying to decide which one to get. i really want the ast 4100 with 350/700 rates but are 2k while bc racing is only 1k dollars and seems as a lot of m3 guys are liking this setup.

[cleex024]

i really want a neutral set up...maybe even a little oversteer, but every company out there seems to make them a little more front stiff biased setups or 1:2 f:r ratios.

dont want understeer but seems like that is the only way companies make their coilovers, but maybe im understanding something wrong where this is the neutral setup.

is there some kind of advantage of having the fronts a lot more stiff f:r ratio compared to stock settings?

[cleex024]

anyone?

[sonorous]

Does anyone know the spring rates on the H&R sport springs for E90/E92? I searched but could not find this information.

[cleex024]

all the rates on h&r and eibachs are similar to stock rates...just a little stiffer

but still wondering if you should get more like 300f/800r rates instead of 1:2 respectively

[parabmw]

Very informative

[E92meesh]

any updates?

[Cyn-BMW]

Yes, let’s have updates. I wanna do something with my 2011 328i E92 LCI. I’m thinking about these springs, because of the minimal drop. But, I have no idea if these spring rates will work with my car. I plan on installing a Hotchkis sway bar kit and some kind of adjustable shocks.

https://www.carid.com/2011-bmw-3-ser...parentsubmodel[]=WHEEL+DRIVE|RWD+%28Rear+Wheel+Drive%29

[stevesingo]

There is a sticky on exactly this... https://www.e90post.com/forums/showthread.php?t=235797

[Cyn-BMW]

When you start looking at spring rates, rates are all over the map. None of it makes any sense.