Does my bike have stock or aftermarket fork springs?

hardrockminer wrote:

TexasKZ wrote:
+1
Springs that old are done. Progressive, Sonic or Race Tech replacements will make a huge improvement.

I don't agree with that statement TexasKZ. As long as a spring has not been strained to the point of deformation it will continue to perform correctly. That's why the standard test is to measure the length and compare to a standard. Just because they're old is no reason for them to be changed out.

Springs are not designed independantly. They are selected to suit the fork damping, along with the mass being moved. Changing springs will change those relationships and could result in an unstable ride at certain speeds.

If riding conditions are different than those used during design there may be more suitable springs out there. It's hard to know what the design conditions were, but likely average rider on average roads. Someone wanting to ride more aggressively would definitely benefit from more suitable springs, but otherwise the original ones will be just fine as long as they have not been deformed.

Agreed. Spent a career in vehicle (automotive) suspension design, test, & development, and agree with your observations.

I just replaced the original fork springs on my Z1b. They were about 3mm over spec in length. I went with Racetech two spring rates higher.