COIL SPRING RATE CONVERSION - A. Hyde 5/2000 update 11/2010

Background Math: relating to force

1 lb = 0.454 kg and 1 kg = 9.81 Newtons (1 Newton N = 0.1 kg = 0.22 lb) 1 lbf = pounds-force (not pounds foot lb/ft)

Force is designated as a Newton in the metric SI system

Converting pounds force into Newtons: Force=Mass x Acceleration -> lbf = 0.454 x 9.81 (accel due to gravity) -> 1 lbf = 4.45 N (Newtons)

Converting Newtons to millimetre (N/mm): N/mm = 4.45 / 25.4 = 0.175 (a unitless conversion factor)

Easy CONVERSION between Pounds-force per inch AND Newtons per millimetre

To Convert lbf/in to N/mm (Pounds-force per inch to Newtons per millimetre)

lbf/in x 0.175 = N/mm, Example: 100 lbf/in x 0.175 = 17.5 N/mm

To Convert N/mm to lbf/in (inverse = 1 / 0.175 = 5.714 )

N/mm x 5.714 = lbf/in, Example:100 N/mm spring x 5.714 = 514 lbf/in
OR
N/cm
x 0.5714 = lbf/in

lbf/in to N/mm Chart

 100 = 17.5 220 = 38.5 450 = 78.75 120 = 21 240 = 42 500 = 87.5 130 = 22.75 260 = 45.5 550 = 96.25 140 = 24.5 280 = 49 600 lbf/in =105 N/mm 150 = 26.25 300 = 52.5 650 = 113.75 160 = 28 320 = 56 700 = 122.5 170 = 29.75 340 = 59.5 800 = 140 180 = 31.5 360 = 63 900 = 157.5 190 = 33.25 380 = 66.5 1000 = 175 200 lbf/in = 35 N/mm 400 lbf/in = 70 N/mm 1200 = 210

EIBACH ERS SPRING DATA
# 200   60    60 (typical part number for Eibach ERS springs

Length mm ID mm           Rate N/mm

200-60-60 Rate 60 N/mm ~ 342 lbf/in, block 85 mm

200-60-70 Rate 70 N/ ~ 400 lb, block 89 mm

200-60-80 Rate 80 N/ ~ 457 lb, block 94 mm

200-60-90 Rate 90 N/ ~ 514 lb, block 92 mm

180-60-70 Rate 70 N/ ~ 400 lb, block 75 mm

180-60-80 Rate 80 N,/ ~ 457 lbblock 80 mm (15% stiffer than 70 N)

180-60-90 Rate 90 N/ ~ 514 lb, block 80 mm (30% stiffer than 70 N)

170-60-80 Rate 80 N/ ~ 457 lb, block 64 mm (170-64=104 travel) (15% stiffer than 70 N) New product length

160-60-70 Rate 70 N/ ~ 400 lb, block 65 mm

160-60-80 Rate 80 N/ ~ 457 lb, block ...

160-60-100 Rate (100 N / ~571 lb, block ...

TENDER SPRINGS

60-60-60 Free length 95 mm, Solid height 37 mm, flat spacing 27 mm c/c

4 active coils, 7.2 to 7.4 flat wire, OD=, ID=60

40-60-30 free length 64, static to block 25.5

HELPER SPRINGS (only one spec available, then catalog to TENDER springs)

60-60-2

60 length, 60 ID 2 N rate / ~ 11 lb block 13 mm