MX Fork Spring Tester

[Jigantor]

I find that some new springs I purchase don't match their rating. I have also discovered as have others that old springs lose their rating over time or repatitions.
That said I made a fork spring tester so I know what the rating is before I install them or during a service.
I used some scrap ali I had sitting around.

First I cut out the base discs with a hole saw in a drill press.

Ji

[Jigantor]

I used tubes that will telescope into each other and 2 base discs that are larger than any fork spring.

Ji

[Jigantor]

I tack welded the discs to the tubes.

Ji

[Jigantor]

Place the tester into the spring and mark where the tubes intersect, then wrap some tape 1" and 2"es above this point.
Springs are rated in pounds per inch length if they have a constant rate.
By marking 1 and 2 inches I can test the spring with acuracy.
I should be able to double the first result which if every thing is correct should equal the second marked spot or the 2" mark.

Ji

[Jigantor]

Place the spring with the tester on to a scale and compress the spring untill you reach the 1" mark and take a reading. Then compress the spring to the 2" mark and take another reading.
This spring at the 1" mark read 14.7lb/in and at the 2" mark read 29.9lb/in.
If we double the first reading 14.7 we get 29.4 which is very close.
The OEM manual states that it should be 14.9lb/in so this spring is looking good.

Ji