I have recently disassembled my suspension fork and found an extraterrestrial piece of rubber in the coil spring. After some highly accurate measuring it was safe to say that this rubber piece is actually preventing the spring to compress properly. I have removed the thing and the measured travel of my suspension fork doubled from 45mm to ~90mm. I didn't yet have the opportunity to test how it works out on the trails, however.

Do you know what this thing and it's purpose is? If it actually has a purpose, would it be a dumb idea to cut it in half so that it doesn't reduce travel?

Extraterrestrial thing

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    Its purpose may be to limit travel, although limiting it to 45mm seems odd. One thing i would check is that without out you are not bottoming out the fork on hard hits. – Nate W Jul 5 '18 at 21:02
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    Is it hard or squishy? If its hard might be a misplaced piece of packing, wheras if it were soft then it could be a "bump-stop" to control the safe limit. – Criggie Jul 6 '18 at 0:45
  • @Criggie It is almost incompressible. – John Jul 6 '18 at 6:04
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    I'd take it completely out and keep it safe somewhere just in case. – Criggie Jul 7 '18 at 6:24
  • When estimating how much things compress you need to consider your much more force you exert when hitting something with much of your weight and a run-up, compared to just trying with your hands. It might compress more than you think in action – Chris H Nov 16 '18 at 6:28

It's an elastomer damper, see figure 6 on the image below. Without a damper, the fork would bob uncontrollably like a pogo stick, which is not good at all when riding a bike. Elastomer dampers are a sign of low-end forks, while more expensive forks use oil damping or other forms of damping. You can replace the stock piece of elastomer with less rigid or shorter one to adjust the fork feel. enter image description here

  • Good find, but how would you reconcile that with "It is almost incompressible. – John Jul 6 at 6:04" ? – Criggie Nov 16 '18 at 9:48
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    @Criggie Presumably, it's hard to compress across its diameter but, in the fork, it's compressed along its length. And it should be pretty hard to compress since it has to deal with fairly large forces. – David Richerby Nov 16 '18 at 9:57

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