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Coil bind/measuring spring rate

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,031
5,921
borcester rhymes
I'm putting together a coil spring project and digging through my box o parts, I found an unlabeled spring. The spring that came off the shock was labeled as 650x2.25. The exposed shaft length is 2.0. The unlabeled spring is about an inch shorter than the 650, but the separation between coils is the same or better on the weird coil.

1) is there any way to know whether I will experience coil bind on this spring aside from "ride my bike" and finding out?

2) is there any way to determine spring rate on this coil? It puts sag at about 30% according to the built in doo-hickey on the stays, but that is very much not accurate. Calculators tell me I need about a 500lb spring.
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,573
1,069
La Verne
put the spring in a vice and fully compress it.
measure the length
if free length - solid height > stroke + preload then you are fine
 

englertracing

you owe me a sandwich
Mar 5, 2012
1,573
1,069
La Verne
Respectfully, don't do that. ^^^
Compress the spring safely, make sure its captured. Borrow a spring compressor, use a threaded rod and big washers, etc. Compressing it in a vise runs the risk of it ejecting.
Safety third.
the probability of that depends on the L/D of the spring
a 5.5 x 2.75 spring show no sings of bowing when compressed in my vice. but i still stayed out of the way.
 

maxyedor

<b>TOOL PRO</b>
Oct 20, 2005
5,496
3,140
In the bathroom, fighting a battle
To determine coil-bind one could also measure diameter of the coils, then count them and do maths to see how that compares to free-length, but that sounds less fun. Just whack it with a hammer next to a tape measure and see if you can take a picture at full-compression.

As for spring-rate, you either need a press or some weights to stack on it to know how far it compresses given a specific weight
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,031
5,921
borcester rhymes
Haha, I compressed it in my ghetto bearing press from 4.77 down to 3.07, but I need 2" so I'll have to try again. There was plenty of space left, but I'm not sure it was 0.3" worth.
 

Leafy

Monkey
Sep 13, 2019
542
350
Gross, compressing a spring to 58% of its free length. Its not going to last forever like that.