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On of my fork stanchions has scratches on the black coating. The scratch has sharp edges.

The Fork is a RockShox Pike RCT3.

I could try to fill the scratch with paint and polish or replace the crown with standpipes. The replacement CSU unit for the Pike costs 316€

enter image description here

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    So - what's your question? Are you asking how to touch up the paint, or how to stop it rusting? Looks to me like minor usage damage - you rode your bike past a thorn or stick , or maybe it hit the ground. Some clear nail varnish might be all you should apply, or even nothing at all. – Criggie Sep 17 '16 at 19:47
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    What you need to do depends on the scratch (and your question too). If there is a burr (sharp barb sticking out) this will tear the seals. If there is just a scratch this may lead to oil and air leakage. Burrs need to be filed off and scratches filled to keep the fork working but a new CSU is the only fix. Plenty of instructions online on how to fix. – DWGKNZ Sep 19 '16 at 1:19
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    Wait - are you saying this scratch is on the inner part of the leg, that has to form a good seal? Cos it looks like the outer part of the suspension from your photo. Please clarify. – Criggie Sep 20 '16 at 4:30
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    @Criggie This is the upper fork assembly. Since a few years ago, Rockshox stanchions are glossy black. You can see the travel gauge printed on it, which is used to set the sag. The lower legs are joined by the brace that has "Pike" printed on it. – Will Vousden Sep 20 '16 at 10:16
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    @vaious comments: Just to be clear, scratches on stanchions is a leading cause of forks getting completely trashed. Sad but true. – Nathan Knutson Sep 20 '16 at 17:41
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It really depends how deep the scratch is. If it's deep enough, then a new CSU (crown-steerer unit) is the only sure-fire fix.

However, here are some steps I've taken in the past, which have given me some success:

  1. Sand the scratch down to remove the burrs. You can use super-fine wet & dry paper for this; something like 2000 grit should do the job without damaging the rest of the surface.
  2. Clean the scratch and the surrounding area thoroughly with isopropyl alcohol, removing any debris from the scratch itself.
  3. Fill the scratch with some high-quality epoxy. I've used J-B Weld in the past with some success. Some people have reported success with super glue or nail varnish, too.
  4. Wet a razor blade (or something similar) with water and use it to scrape off the excess. You want it to be as smooth and flat as possible.

Your mileage may vary here; if the filling comes off after riding, you might be looking at a new CSU if you want a complete fix. The fork will still work, of course, but a gap will allow dirt into the lower legs, which will effectively shorten the service interval on the fork.

I've successfully repaired a nick in a Fox RP2 rear shock like this, and it's still going strong today. However, it didn't work so well on the stanchions of my TALAS 32, since the filling wouldn't stick for more than a couple of rides.

  • If you're going to downvote, please explain what's wrong with the answer! – Will Vousden Sep 20 '16 at 12:26
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Scratched stantions are no big deal as long as you smooth the edges and the scratch isn't deep you will be fine. I scratched my stantion on my reacon gold and feels fine. It's more aesthetic than practical. Just ride!

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If you just want to hide the chip a little just touch it a couple of times with a black sharpie pen. If that's not good enough, get a suitable vehicle touch-up colour & the lacquer, and do it properly.

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    Sadly this is more than just cosmetic damage. A scratched stanchion can damage the seals and cause oil leakage and contamination. – Will Vousden Sep 20 '16 at 10:17
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Ah sorry.. I didn't realise the image was of the inner fork leg.

The only permanent option here apart from a new part is to remove the inner fork leg and take it to an engineering workshop.. A good shop should be able to grind the leg down in the damaged area. Then either fill it and machine it back to size, or spray weld it which is a different process to fill the damaged area, then again machine it back to original diameter. Filling by welding can be done with most materials in one way or another.

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