After owning my bike for 8 years and admittedly not always paying the most attention to it, I was thinking about buying a new bike soon. So I thought before buying the bike I'll see where damage is to my current bike so I can try and avoid damaging it the same way in the future.

A lot of videos I've watched online advise you to protect the toptube, downtube, chainstay etc. Looking at my bike though I have a lot of damage under the crankset and was wondering if this is a common thing? Is there something I could have done to prevent it etc. It looks really badly scratched up and I'm not sure what caused it so any ideas about that?

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    I'll put it as a comment since for lack of provided information, I can only speculate: either the front derailleur drops the chain frequently or you pick up debris with the drive-train. – Carel May 21 '20 at 18:52

My guess is that this was caused by chain suck. This is a problem where the chain doesn't roll off the bottom of the chainring as readily as it should, and the chainring draws it up toward the chainstay. It can get wedged between the chainring and chainstay, and take off paint in exactly this way.

This can be caused by worn cogs, a worn chain, a too-long chain, or too little tension in the rear derailleur holding the chain taut.

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    That's my thought too, although the chainrings don't show much wear. – Daniel R Hicks May 21 '20 at 19:40
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    Yes, that makes sense thanks. I recently changed the drivetrain, the previous one was worn out quite bad which likely caused the chain suck as you said. – Jack Hudson May 21 '20 at 19:54
  • Concur - as a fix, OP might consider removing chainring or whole driveside crank, lightly sand/buff the area and surrounding edges of paint, and then apply some hard-wearing light-coloured paint. I'd go with ~3 layers, with light sanding between and give them a day to set. Also I'd apply with a small brush because aerosol overspray is likely. A light colour will blend better, and will show if this is still happening over time. – Criggie May 22 '20 at 4:06
  • One of my bikes has a stuck-on oval metal plate as protection on the chainstay at that same spot. So I think that you can buy those from your LBS or from the Net. – Carel May 23 '20 at 14:29

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