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Old 07-14-2017, 12:02 AM   #1
Agent_D
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Question about springs installed backwards

So I took my car to have my RCE Yellow springs put on today. I dropped it off before work, then picked it up after. When I got home I inspected, as I always do when I have other people touch my car. The rear springs were installed upside down from the instructions. The tighter coiled area is near the bottom of the damper instead of the top. Will this hurt anything? Should I remove them and turn them around?

Personally, I can't really see how it would have an adverse affect since they are not progressive springs, but I'm also not a suspension expert. The only thing I can really come up with is a negative impact on rebound, but I'm not entirely sure that is correct either.

Thanks for any info!
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Old 07-14-2017, 01:49 AM   #2
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I would assume that if you installed it backwards, it would be stiffer since the tighter coils are on top instead of on the bottom. however, I am not exactly 100% sure on that.
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Old 07-14-2017, 02:31 AM   #3
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Should I remove them and turn them around?
Don't bother. The closer wound coils close first regardless if they're on the top
or bottom.
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Old 07-14-2017, 07:59 AM   #4
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The spring will function the same, however the closer wound end of the spring does have more mass to it than the wider spaced end. If that's on the bottom, you're increasing the amount of unsprung weight, incrementally. Someone else can do the math to figure out exactly how much more mass there is on the tight end, but in the end, I seriously doubt it'd be noticeable.
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Old 07-14-2017, 11:48 AM   #5
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Old 07-14-2017, 02:47 PM   #6
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RCE said they recommend changing it, as it changes the way the car responds to small bumps.
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Old 07-14-2017, 03:59 PM   #7
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RCE said they recommend changing it, as it changes the way the car responds to small bumps.
Makes sense. A unidirectional spring is a spring but may respond differently to high frequency movements.
I would still change it since the manufacturer designed it that way.
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Old 07-14-2017, 04:59 PM   #8
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RCE said they recommend changing it, as it changes the way the car responds to small bumps.
@Racecomp Engineering
Hey Andrew, would you please elaborate on this.
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Old 07-14-2017, 05:02 PM   #9
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I'd only change them if they were upside down.

Or maybe downside up.

Backwards is OK.
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Old 07-17-2017, 11:28 AM   #10
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@Racecomp Engineering
Hey Andrew, would you please elaborate on this.
I've been out of town for a week so just seeing this now. I don't think you'd feel any difference in stiffness, but I would be more concerned with fitment or possible noises from an upside down spring. I would fix it. Rears are easy anyway.

- andrew
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Old 07-17-2017, 08:12 PM   #11
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No from a physics perspective the spring after being installed in the strut will give the same force in the up and down direction.

Thanks to Newtons 3rd law of motion, The equal and opposite one...

The spring doesn't care if it fees the downward force of a 700lb guy in your trunk (where the spring will apply an equal force in the upward direction) or an equivalent force caused in the upward direction by driving over a dead body on the freeway (were the spring will exert an equal and opposing force in the down direction).

As a fun physics exercise take apart a retractable pen (the ones that click up and down). Find the spring that controls the clicking/retracting feature of this pen and flip the spring upside down and then reassemble the pen..... does the pen still work? Does it feel like the pen requires more pressure from your finger to click the button down?

Many of these pens have springs that have tighter/closer coils on one and and wider/further apart coils on the opposite end. Try this with an even spring and a gradated spring. It will all be the same no matter the spring direction.

If you found this physics chat useful please feel free compose a letter of recommendation as to help me achieve my graduate school application goals.
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Old 07-17-2017, 09:39 PM   #12
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If you found this physics chat useful please feel free compose a letter of recommendation as to help me achieve my graduate school application goals.
Too practical for grad school, straight to teaching or industry with you!
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Old 07-19-2017, 02:04 AM   #13
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Too practical for grad school, straight to teaching or industry with you!
HAHA We are both in the bay area... You know the pay can get quite tempting for industry jobs out here. Undergrad schooling made me able to articulate practical advice quit well in relation to concepts in physics but my dreams and heart are in theoretical quantum gravity research.

Life Goals:
-Get Dr. in front of my name
-Conduct and contribute to gravitational wave/graviton Research
-Get on the cover of Times magazine
-Surpass Neil Degrass Tyson's media presence with a dash of Tony Stark thrown in



On a side note I noticed that a lot of spring rates for springs are kind of missing. There may be a simple way to calculate the spring rates for all those springs.

The equation for the spring force is:

k*Distance=Spring force or force on spring
-(k) is the variable used in physics for the spring constant which I believe is interchangeable with how the automotive industry used the phrase "spring rate".

And the downward force of any mass due to earths gravity is:

Mass*9.8m/s=downward force

So if someone has one of those fancy 4 wheel alignment machines that displayed weight distribution and if someone would make a set of dummy shocks that lifted the car to the point where the springs are not compressed yet they are installed at the max uncompressed height. One could use this equation:

k*distance = Mass*9.8m/s

to make this equation:

k=(Mass*9.8m/s)/distance the spring compressed in meters

where the mass could be the original weight of the car plus some extremely fat friend you talked into hopping in the car while on the alignment/scale machine. You can measure the distance each spring compresses and enter the info in the above equation and that should give a rough idea of the spring rate for each spring.

This is what physics calls the static spring rate.

BUT!!! If spring rates and shock rates in the automotive industry are based on a time derivative (fancy way of saying how something changes over time) then that would require a differential equation and a measurement of how fast this spring or shock is recovering after being compressed (the measurement after you let go of a spring and how much time it takes for the spring to rebound to its max height.

I don't see why a spring would need this version of measurement but the shock will need to go through this measurement since it "damps".

damp = slows down the wave (of a bouncing/oscillating spring)

So you're measuring the change in force over time as the spring exerts from its max force (once let go) till no force is exerted (spring reaches max uncompressed height).

That equation looks a little funkier and needs a precise timer. So lets just forget about the shocks for now.

So ya if @Racecomp Engineering has one if these machines, a shock that provides no damping force and some free time to work some of this stuff out it is not impossible to find the spring rate of any spring on the market.

I'll be expecting my letter of recommendation before the November deadline thank you very much. End Tangent lol
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Old 07-19-2017, 03:25 AM   #14
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Ok, you're back into grad school, nobody wants to hire someone who would go through all that trouble.

I just used a drill press, ruler, and a scale rated to a few hundred or ideally thousand pounds, but you do you. Race teams will get into how each spring acts dynamically but the rest of us can't afford a sample size to actually do anything about it (other than put the slightly stiffer spring on the heavier side of the car), maybe something useful there for measuring lifespan of a spring (I'd presume elasticity degrades over time but who knows) but the deltas are probably too small on quality springs to be measured with amateurs equipment.
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