[alscks0414]

Originally Posted by Who?

I asked the guys at st suspension about these rates, so take that as you will

I know eibach aims to be within 80% stiffness with their dpring rates, so these seem abit stiffer.. not sure if the stock shocks will be able to take them over the long term. Im just changing springs

You are going about 39% stiffer at the front and 20% rear. That is a significant difference. Harder spring will give more stress to shocks at their rebounds. If you are using them weekend back-road winding and just daily, I think they will be okay but cannot guarantee. If you are bringing yours to track, not recommended for sure.

There should be many ppl with HAS kit, and surely some of them have done some track use. Maybe they can help you out better.

FYI, OE shocks are known to be one of the parts of M2 that is not really designed to be abused with aggressive driving like using on track (at least by seeing my friends around me who tracks theirs often). I have couple of friends changed their shocks. One friend got new OE shocks only after 1 year, about 10 different track days which includes 5 of full 6 hours. Another one got KW V3 after 1 year of use as well but do not know he many times he made his day to the track.

If you are planning to go change the springs anyways and also plan to go track/ autocross, I highly recommend to get aftermarket coilover (or MP coilover) with proper camber plates.

[M Fifty]

If you have a set of callipers and a spring to hand, you might find this useful:

http://www.reliablespring.co.uk/calculator.htm

[m3driver999]

Hello All,

Have the same question as well,
Don't have an M2 but bought a set of M2 DCT springs, to try out in a 2 series.

The rear springs seem linear, so measured the rate installed in the car,
(car on hoist with wheel on scale, and very slowly raise/lower and take measurement of wheel location) Being linear, droop and compression would be same rate.

For the M2 DCT rear spring, I measured 268lbs/in wheel rate.

The front, have not measured yet - as it is more involved to install than rear.

However, I did use a similar calculator, and from my rough measurements
N = 3.85, OD = 164mm l = 255mm wire = 14mm, E= steel ~ 11.25^6; I get approx 170 lbs/in.

However the front springs are progressive it seems from coil windings; And using the hoist/scale method would only give the rate during droop not compression..

Cheers,

[m3driver999]

Had found some information on spring rates,

Seems the aftermarket springs makers have to make a certificate with specs.
Germany's TUV certificate,

For example for H&R it is on their website under service/product

i.e. the 28802 product for M2 document,

http://www.h-r.com/bin/28802.pdf

From there and with the calculator you can get a ballpark estimate of drop and rate (assuming springs compresses linearly)

Also, let's not forget influence on the spring rate of the rubber secondary spring..ie on a 235i seems 8mm of travel will start engaging rubber bumpstop.

[Tag]

Did a little reverse math to figure out the stock spring rates. The Dinan HAS for the F87 states the following.

+ Spring rates are nearly 18% stiffer in front and 5% stiffer in the rear.

Their website however doesn't list the actual rates Dinan uses, but if you search you will find several vendors stating the following.

Spring Rate (lbs/in): 250 lb/in FRONT; 750 lb/in REAR

Did the math, these are the results.

F87 Stock Suspension Spring Rate (Progressive)
FRONT: 35 N/mm | 200 lbs/in
REAR: 125 N/mm | 714 lbs/in

Note: The Dinan springs are linear.

[jetbill]

Originally Posted by Tag

Did a little reverse math to figure out the stock spring rates. The Dinan HAS for the F87 states the following.

Their website however doesn't list the actual rates Dinan uses, but if you search you will find several vendors stating the following.

Did the math, these are the results.

F87 Stock Suspension Spring Rate (Progressive)
FRONT: 35 N/mm | 200 lbs/in
REAR: 125 N/mm | 714 lbs/in

Note: The Dinan springs are linear.

The Dinan rates are:
M3/M4 front = 250 lb/in
M3/M4 rear = 650 lb/in

M2 front = 250 lb/in
M2 rear = 750 lb/in (you are correct)

Stock rates:
M4 front = 169 lb/in
M4 rear = 590 lb/in

M2 front = 213 lb/in
M2 rear = progressive 570-580 lb/in averaged

[swifty]

OP,
what did you end up going with?