ID shock spring rates

Micahdogg
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Micahdogg
Is there a way to measure shocks springs to find out what rate they are, in the absence of any markings?
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Falcon
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Falcon 3/26/2018 2:56pm
3/26/2018 2:56pm
Springs are rated in a very simple formula: Kg/mm in the case of MX. For each measurement of weight, the spring will compress accordingly. You can measure the rate of a spring by adding weight to it until it compresses one mm, then measure the weight you added. (This is assuming the spring is free from the shock with no other loads on it.)

It may be much easier to do this and add weight until it reaches 10mm, then find that weight and divide by ten.
Micahdogg
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Micahdogg 3/26/2018 5:54pm
3/26/2018 5:54pm
Perfect! Thanks for this info. So a 5.0 kg shock spring will take 11 lbs to move every 1mm, but a 6.0 kg spring will take a bit over 13 lbs?
KDXGarage
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KDXGarage 3/27/2018 4:44pm
3/27/2018 4:44pm
That absolutely will not work in that manner.

After some initial travel, one can do this, but the quantity of weight really adds up quickly for doing shock springs. On fork springs, it is quite accurate.

See if there is a suspension shop close by that has a large spring rate tester.
Micahdogg
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Micahdogg 3/27/2018 7:46pm
3/27/2018 7:46pm
So how do I do this myself? I can stack weight and see which one travels the least and at least I'll know the stiffest spring out of 4 of them. But it would be nice to know a little closer to what I actually have.

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aees
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aees 3/28/2018 8:51am
3/28/2018 8:51am
If the springs are of the same height and dimensions, you could just way them and see which one is heavier. That should be the stiffest one.

You can also measure the coils to see which one is thickest.

Not an exact science, but it works if you have several similar models. a 42nm you can for sure differ from a 45 or 48 spring with this model.
kb228
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kb228 3/28/2018 9:17am
3/28/2018 9:17am
The correct way to do it is calculate what spring you need and order it. Sell the 4 you have and be done with it.

Without a spring rate tester youre not getting any type of accurate measurement.
Micahdogg
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Micahdogg 3/28/2018 9:56am
3/28/2018 9:56am
kb228 wrote:
The correct way to do it is calculate what spring you need and order it. Sell the 4 you have and be done with it. Without...
The correct way to do it is calculate what spring you need and order it. Sell the 4 you have and be done with it.

Without a spring rate tester youre not getting any type of accurate measurement.
I know what I need. But if I already have it, I'm not going to order another one.
aees
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aees 3/29/2018 3:06am
3/29/2018 3:06am
kb228 wrote:
The correct way to do it is calculate what spring you need and order it. Sell the 4 you have and be done with it. Without...
The correct way to do it is calculate what spring you need and order it. Sell the 4 you have and be done with it.

Without a spring rate tester youre not getting any type of accurate measurement.
Micahdogg wrote:
I know what I need. But if I already have it, I'm not going to order another one.
Do as i said, way them or measure coils. Mount the stiffest one if that is what you think you need. Check SAG numbers and if they are ok, it is worth test it on track.
KDXGarage
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KDXGarage 3/30/2018 1:09am
3/30/2018 1:09am
Are all four for the same bike? If so, which bike??

Are all four the same height and width? If so, then if one has thinner or thicker coils, you can place them in an order.

Some KYB factory springs came with a paint dot on them.

Micahdogg
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Micahdogg 3/30/2018 6:53am
3/30/2018 6:53am
I honestly don't know. This is for a 1992 CR500. One is on the bike, of the other 3 springs, at least 2 look the same as what is on the bike. If they are dimensionally the same, I'll expect that they can be used. Looks like I need a 5.9 kg spring and if I can tell for sure that one of these is like a 5.7 or something, then I might use it. If I don't have anything bigger than a 5.5 I will probably buy a spring.

A quick look at them didn't show any markings at all.

Having to install them all and try to adjust sag sounds like a pain in the butt!
Micahdogg
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Micahdogg 3/31/2018 7:16pm
3/31/2018 7:16pm
I found some numbers on the shock spring that is on the bike right now. Its a white spring that says 58-280. I loosened it way up and got 1 inch of free sag and got a little over 3.5 with me on the bike. So I guess that means its a 5.8 kg spring, which is good enough for me.

I'll probably weigh it and see how it stacks up against the other 3 springs so I can figure out what those are.

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