Spring rate help please!

[Bobbo]

Saw the sticky on the E90 forum.

Now are the stock 135i spring rates listed for standard or M sport package.

Also are the spring rates listed for the after market suspensions KW etc the same for e82's.

If not does anyone know the spring rates for the BMW performance suspension and KW street comforts for e82's?

Also is is possible or advisable to use the bmw performance springs with KONI FSD's?

[arrutled]

some have already gone the fsd plus performance spring, hopefully they will chime in. There is a discussion on e90 post about trying to figure out those performance rates. search for that one. i think for the e82 its 160-420. you'll have to ask a KW vendor about the other question though.

[WhiteOne]

M sport is supposed to be 120/350.
BMW performance is about 195/505.(found on another thread)
Street Comforts have 285/???.(I can't remember rear)
FSD's work well with stock springs according to members using them.
Shorter stiffer springs might require different dampening.

[Bobbo]

Cool thanks for replies. I am pretty keen to go down the koni FSD path.

I would really like to hear if anyone has used the BMW performance springs with FSD's successfully.

Anyone have an opinion on H&R sways vs OEM M3 sways.

One more do you feel a difference upgrading front control arms to M3 bits or is it minor and $$$$ better spent else where?

[jah29]

Originally Posted by jbgti

Cool thanks for replies. I am pretty keen to go down the koni FSD path.

I would really like to hear if anyone has used the BMW performance springs with FSD's successfully.

Anyone have an opinion on H&R sways vs OEM M3 sways.

One more do you feel a difference upgrading front control arms to M3 bits or is it minor and $$$$ better spent else where?

I used FSD with the performance springs and they worked great together. I have since upgraded the rear springs to 550lbs, because the front/rear ratio of the performance springs still produces under steer on the track. I don't think my 550lb springs work as well with the FSD, but the 420 seemed perfect.

[Bobbo]

Thanks for chiming in good to hear someone has gone this path.

You think the FSD's are better than the performance shockers?

So the drop in ride height from the springs doesn't effect FSD's?

Are you running m3 front and rear sways?

[M3R1]

Originally Posted by jah29

I used FSD with the performance springs and they worked great together. I have since upgraded the rear springs to 550lbs, because the front/rear ratio of the performance springs still produces under steer on the track. I don't think my 550lb springs work as well with the FSD, but the 420 seemed perfect.

Originally Posted by jbgti

Thanks for chiming in good to hear someone has gone this path.

You think the FSD's are better than the performance shockers?

So the drop in ride height from the springs doesn't effect FSD's?

Are you running m3 front and rear sways?

I'm interested in this set up as well, subscribed for answers...

[jah29]

Originally Posted by M3R1

I'm interested in this set up as well, subscribed for answers...

yes front and rear M3 sways.

FSD are designed for stock springs but can be bought as a set with the Eibach springs. The Eibach lower more than the BMW yellow springs do, so there shouldn't be any problems with height, and I haven't had any.

I think the FSD are at least as good as anything BMW sells. They are definitely higher quality, I just don't know if they're are 10% or 40% better. I like the way they ride on the street and on the track. I think the rear dampers are a little over worked with my 550 springs compared to the 420 yellows. They don't feel as good as when I had the BMW yellows on all four corners.

And I bought them used for $400, so definitely a great upgrade.

I said most of this stuff in another thread recently. I might have provided more/different details so you should look for it.

justin

[Bobbo]

Thanks for the info Justin.

One last question:

"Will the BMW Performance springs work well with H&R sway bars or is the increase in spring rate be too much?"

Will also be installing M3 control arms and rear bushings.

[jah29]

Originally Posted by jbgti

Thanks for the info Justin.

One last question:

"Will the BMW Performance springs work well with H&R sway bars or is the increase in spring rate be too much?"

Will also be installing M3 control arms and rear bushings.

I think the H&R bars are slightly stiffer than the M3 bars and roughly the same ratio front to rear.

Any springs and sway bars will work on the car. The question is what are you going to do about damping. The number for comfort on a road car is about 30% critical damping, on a track car about 65% critical damping. If you increase the wheel rate with bars or springs your gonna have to find a way to get more damping. You have quite a range that will work, 30-65%, but if you are shooting for specific performance it'll take some research and maybe something custom.

I guessed the FSD put the stock springs at 60%, then I upgraded the springs and swaybars so I guess I might be at 40%. That would be biased more toward road than track. Worked well enough on the track for me since I have another vehicle which is my primary track car.

if you're ready to do some math read these to understand what I'm talking about damping:

http://www.optimumg.com/OptimumGWebS.../TechTips.html

[Bobbo]

Once again thanks for your advice.

My car will nearly always be on the road. So yes I am looking for a awesome street setup. So it sounds like FSD's yellow springs H&R sways are a go ahead. Was only concerned about the performance springs because I thought the H&R sways and FSD's worked best with stock springs. But after hearing your experiences I will try the performance springs too.

I tried looking at that maths stuff. Started to bring back bad memories from high school. Maybe if I had a project like this for my math projects I would have done better!

Will post my results.

[NIB]

Originally Posted by arrutled

some have already gone the fsd plus performance spring, hopefully they will chime in. There is a discussion on e90 post about trying to figure out those performance rates. search for that one. i think for the e82 its 160-420. you'll have to ask a KW vendor about the other question though.

really interested, how about just replacing mine stock springs on Bilstein6 struts on mine 2009 128i without lowering. advice on which specification I should look for and from which vendor. I repeat I do not want to lower but replace mine probably weak springs, Front and Back

[ShocknAwe]

Originally Posted by NIB

really interested, how about just replacing mine stock springs on Bilstein6 struts on mine 2009 128i without lowering. advice on which specification I should look for and from which vendor. I repeat I do not want to lower but replace mine probably weak springs, Front and Back

You do understand this thread is nearly 6 years old, correct?

[NIB]

Originally Posted by ShocknAwe

You do understand this thread is nearly 6 years old, correct?

Correct, but I just got the Car and do not want to use Performance rings due to the nature of the road to mine Den, that is why I want to change the Stock rings to another stock ring, so as to maintain the height. Do advice.

[ShocknAwe]

You can't. As far as springs go, your option is to keep stock, or go with a coilover setup that is capable of stock height.