Spring rate help, where do I start?

[David Barrish]

My new car is getting close, but I could use some help. The new car is a 1975 2002, apx 2300 lb, rear wheel drive with 110 hp at the rear wheels. I wish it was more but why lie to myself.

I am moving on to coil-overs in the front with Bilstein Sport inserts, the rears will be 5" coils with Bilstein's also. The shocks and inserts are not adjustable. The sway bars are 22mm and 19mm. The front has two points of adjustment, the rear is fully adjustable.

The previous set-up was 325 front and 250 rear. If you have any ideas, please let me know.

Thank you.

David

[Aaron Goldsmith]

this is where you start: http://farnorthracing.com/autocross_secrets5.html" onclick="window.open(this.href);return false;

[David Barrish]

Aaron,

Thank you.

David Barrish

[John Kestler]

David. I can't wait to see it. I've moved on to another project and have mothballed toe 2002 for another day. Here is some infor for you....
Straight from the BMW2002FAQ:
Also see 2002 specific calculator at: http://www.bmw2002faq.com/content/view/43/32/" onclick="window.open(this.href);return false;


Written by Jeff Ireland
Tuesday, 13 September 2005

Introduction:

The following is a very basic listing of what constitutes a true racing suspension for a trackworthy 2002. Be aware that different sanctioning bodies will require different setups, so check your rule books! Or, don't and just race against yourself!

Front Suspension:

Adjustable height coil over for standard 2.5”ID racing springs
Springs – 400 to 425 lb/inch x 7”
Shorten struts approximately 2”
Shocks – special shorter body (VW Rabbit) Bilsteins
Bend struts 1 to 1.5 degrees for maximum camber adjustment
Adjustable racing camber plates with solidly-mounted spherical bearings
Camber setting – 3.5 degrees total camber and toe out 1/16” to 1/8”
Strut brace – should be straight not bent
Urethane bushings for control arms and strut rod
Sway bar – Ireland Engineering 22mm hollow bar or 25mm solid bar

Rear Suspension:
Custom adjustable camber and toe installation necessary to achieve:
Camber and toe settings of – 2.25 to 2.5 degrees camber and toe in 1/16” to 1/8”
Stock-location springs – 350 lb/inch –
Optional weld-reinforce stock shock towers for coilover rear shocks – adjustable height coil over springs on shocks – 275 lb/inch x 8”
Coilover shocks – Bilstein sport
Sway bar – Ireland solid 22mm adjustable bar
Urethane bushings for trailing arms and differential mount
Solid aluminum rear subframe mounts

And, as always, if you have any questions or comments, please feel free to post them to the Message Board!

[Vincent Komara]

So the BMW 2002 also uses the Bilstein sport P30-0032 strut insert? I have a new set of 4 I am looking to sell if there is any interest.

[Christos Adam]

this is where you start: http://farnorthracing.com/autocross_secrets5.html" onclick="window.open(this.href);return false;

Are these theories correct?
The guy is suggesting to have 2,2 Hz at the front and 2,5Hz at the rear... I just calculated the my wheel frequency at 6.13 Hz for the front and 4,56 for the rear }:)

I used this calculator:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;

EDIT
I played with the numbers a bit and found out that to be at 2,5Hz I need 150 lbs/inch - basically stock springs

[Jeff Wong]

this is where you start: http://farnorthracing.com/autocross_secrets5.html" onclick="window.open(this.href);return false;

Are these theories correct?
The guy is suggesting to have 2,2 Hz at the front and 2,5Hz at the rear... I just calculated the my wheel frequency at 6.13 Hz for the front and 4,56 for the rear }:)

I used this calculator:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;

EDIT
I played with the numbers a bit and found out that to be at 2,5Hz I need 150 lbs/inch - basically stock springs

You are probably around 3hz in the front and 2.5hz in the rear. 6hz is like 3000lbs+ spring.

[Christos Adam]

this is where you start: http://farnorthracing.com/autocross_secrets5.html" onclick="window.open(this.href);return false;

Are these theories correct?
The guy is suggesting to have 2,2 Hz at the front and 2,5Hz at the rear... I just calculated the my wheel frequency at 6.13 Hz for the front and 4,56 for the rear }:)

I used this calculator:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;

EDIT
I played with the numbers a bit and found out that to be at 2,5Hz I need 150 lbs/inch - basically stock springs

You are probably around 3hz in the front and 2.5hz in the rear. 6hz is like 3000lbs+ spring.

I don't know Jeff
If you put here:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;
500
50
1000
0.7
you get 6,67 hz

3000lbs spring will give 11,83 hz (I guess it's not really linear).

[KJ Christopher]

Bend struts 1 to 1.5 degrees for maximum camber adjustment

Huh?

[KJ Christopher]

You are probably around 3hz in the front and 2.5hz in the rear. 6hz is like 3000lbs+ spring.

I don't know Jeff
If you put here:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;
500
50
1000
0.7
you get 6,67 hz

3000lbs spring will give 11,83 hz (I guess it's not really linear).

The leverage ratio is the inverse of the motion ratio. Try 1.43.

[Jonathan Lugod]

You are probably around 3hz in the front and 2.5hz in the rear. 6hz is like 3000lbs+ spring.

I don't know Jeff
If you put here:
http://www.racingaspirations.com/?p=292" onclick="window.open(this.href);return false;
500
50
1000
0.7
you get 6,67 hz

3000lbs spring will give 11,83 hz (I guess it's not really linear).

The leverage ratio is the inverse of the motion ratio. Try 1.43.

damn beat me to it

[Christos Adam]

Thank you KJ and Jeff!

Do you know why the article suggesting higher frequency at the rear?
Rule of thumb is rear NF slightly higher than front
Shouldn't be the opposite for the strong RWD car?

EDIT: I guess on a normal car this difference between front to rear (with rear higher) is to reduce the pitch.

[KJ Christopher]

Thank you KJ and Jeff!

Do you know why the article suggesting higher frequency at the rear?
Rule of thumb is rear NF slightly higher than front
Shouldn't be the opposite for the strong RWD car?

EDIT: I guess on a normal car this difference between front to rear (with rear higher) is to reduce the pitch.

So the car settles at both ends at the same time even though it hits the same bump at different times front/rear? Dunno.

[David Barrish]

Vincent, Please give me a call at 909 289-2775 about the inserts.

Jeff, Thank you for the information on the '02 set-up. You are welcome to drive my car, anything to get you car back on track and finished!

David Barrish