Calculating Coil Rate

[John H]

I am shopping for new coils for the Patrol and want to go a little lower and a touch softer in spring rate.

- I know what my current 6inch springs are 290lbs front & 360lbs rear.
- I also know the obvious stuff like my wire diameter and number of winds etc.

My problem is that most 4x4 stores are happy to tell you that they have a ‘firm 5-inch lift’ but are useless at supplying info on spring rate.
So, is there any way that I can use measurements taken from the coils in the store to calculate (or guess at) the spring rate?

[ozy1]

To Calculate Coil Spring Rate-


RATE= (9909 x material dia. x material dia. x material dia. x material dia.)
divided by

(no. of active coils x mean dia. x mean dia. x mean dia.)

Mean dia. = I.D. + material dia.
All measurements are in millimetres
Result is in N/mm
To convert answer to Kg/mm = N/mm x 0.10192


got this from http://www.industrialsprings.com.au/calc.htm

hope it helps

[John H]

To Calculate Coil Spring Rate-


RATE= (9909 x material dia. x material dia. x material dia. x material dia.)
divided by

(no. of active coils x mean dia. x mean dia. x mean dia.)

Mean dia. = I.D. + material dia.
All measurements are in millimetres
Result is in N/mm
To convert answer to Kg/mm = N/mm x 0.10192


got this from http://www.industrialsprings.com.au/calc.htm

hope it helps

Now, THAT'S WHAT I'M TALKING BOUT!
Cheers

[Charlie]

You might try Ultimate Suspension or Allsprings ,they know a lot more than your average salesman and can custom make if need be.Customs no more expensive actually.
Regards Charlie

[1MadEngineer]

To Calculate Coil Spring Rate-


RATE= (9909 x material dia. x material dia. x material dia. x material dia.)
divided by

(no. of active coils x mean dia. x mean dia. x mean dia.)

Mean dia. = I.D. + material dia.
All measurements are in millimetres
Result is in N/mm
To convert answer to Kg/mm = N/mm x 0.10192


got this from http://www.industrialsprings.com.au/calc.htm

hope it helps

so what about the material constant?

[Cheezy4x4]

Use a spring rater. We do and it will suprise you how different spring rates vary.

[YankeeDave]

most fundemental formula for springs is

f=-kx

where force = - spring rate x displacement

force can be: applied mass x gravity (9.8m/s) which will give you a force in N (neutons) or use imperial units if you'd like.

[bigpat]

I normally use a wire constant of 12 X (10 to the power of 6).

Note that the number of effective coils IS NOT the total number of coil windings. No. of effective coils is total number minus 1.5 coils.
This is to allow for the ends of the wire which are weaker in spring rate.

Cheers,

Pat