Spring rate math question..
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Spring rate math question..
So..I wanted to see how a 'stiffer' spring felt, so I stuffed a pair of those spring helpers in between a coil on each rear spring, and re-lowered the car to the previous height today.
It -dramatically- resolved much of my off-throttle oversteer.
So..with I think..one coil..not in service any more, what spring rate do I roughly have?
87 S4, dual blue paint marks on the springs.
It -dramatically- resolved much of my off-throttle oversteer.
So..with I think..one coil..not in service any more, what spring rate do I roughly have?
87 S4, dual blue paint marks on the springs.
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2-blue stripe rear S4 shocks (actually mid 84-95) have the following dimensions and spring rate:
Spring rate in lbf/in, 170-174
Free length: 412 mm (16.22")
Wire diameter: 13 mm (0.511")
# Coils: 9.5
ID = 92 mm (3.622")
OD = 92+26 = 118 mm
So if you cut exactly one coil, you drop to 8.5 coils, length 368.6 mm. Not sure how to calculate the change in spring rate. Some of the formulae require knowing the number of 'free coils' (it's less than 8.5, you subtract out the coil that's touching the spring perches), and some ask for Young's modulus. I have no idea.
Spring rate in lbf/in, 170-174
Free length: 412 mm (16.22")
Wire diameter: 13 mm (0.511")
# Coils: 9.5
ID = 92 mm (3.622")
OD = 92+26 = 118 mm
So if you cut exactly one coil, you drop to 8.5 coils, length 368.6 mm. Not sure how to calculate the change in spring rate. Some of the formulae require knowing the number of 'free coils' (it's less than 8.5, you subtract out the coil that's touching the spring perches), and some ask for Young's modulus. I have no idea.
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It certainly feels like it..its not so much of an interesting moment. I'll admit asses are not the best calibrated devices available..
I also like how the rate Ive ended up with, still takes a highway bump or bridge approach softly, but less of a 'sag' into an out of it.
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From: Boulder Creek, CA
2-blue stripe rear S4 shocks (actually mid 84-95) have the following dimensions and spring rate:
Spring rate in lbf/in, 170-174
Free length: 412 mm (16.22")
Wire diameter: 13 mm (0.511")
# Coils: 9.5
ID = 92 mm (3.622")
OD = 92+26 = 118 mm
So if you cut exactly one coil, you drop to 8.5 coils, length 368.6 mm. Not sure how to calculate the change in spring rate. Some of the formulae require knowing the number of 'free coils' (it's less than 8.5, you subtract out the coil that's touching the spring perches), and some ask for Young's modulus. I have no idea.
Spring rate in lbf/in, 170-174
Free length: 412 mm (16.22")
Wire diameter: 13 mm (0.511")
# Coils: 9.5
ID = 92 mm (3.622")
OD = 92+26 = 118 mm
So if you cut exactly one coil, you drop to 8.5 coils, length 368.6 mm. Not sure how to calculate the change in spring rate. Some of the formulae require knowing the number of 'free coils' (it's less than 8.5, you subtract out the coil that's touching the spring perches), and some ask for Young's modulus. I have no idea.
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Assuming flat perches. I have not seen my perches yet, but usually if you have full coils the perches will be shaped to fully contact the lowest/highest full coil on the ends and therefore make them act like ground/flat ends.
