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I replaced my Ultegra R8000 inner chainring from 36T to 34T. After installing, I made sure there was enough clearance between the inner chainring and the chainstay and spun it to make sure all is good. However, after today's ride, I realized that the chainring has gotten closer and scratched the paint off the frame. The components are fairly new, so there shouldn't be anything wearing out yet.

What could be the problem and what did I do wrong?

Thanks in advance.

  • 2
    Check the chainring bolts. – Carel Apr 1 at 12:54
  • Also, what frame is this? This is rare, but some frames may not clear a 36t inner ring. The Cinelli King Zydeco gravel bike is one. Just today, some people were puzzling over this very, very odd specification choice on another forum I frequent. My take is that the frame is effectively a 1x. Regardless, you could check the specifications with the manufacturer, if we can't find any public info. – Weiwen Ng Apr 1 at 13:30
  • @WeiwenNg when the bike first came with the 46/36, there was no problem. Only after replacing it to 34T that it rubs, so I believe the fault is mine. I'll probably recheck the bolts torque as Carel said. – Sir Christopher McFarlane Apr 1 at 13:36
  • Photos of the chainring and frame and going to help. Is the replacement a Shimano R8000 component or from another manufacturer? – Argenti Apparatus Apr 1 at 14:36
  • It's possible that the new ring has more of an inward offset than the old one. The offset from the mounting surface to the centerline of the teeth is apt to vary by 1-2mm between ring styles. – Daniel R Hicks Apr 1 at 15:02
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Okay, thanks for everyone's time for commenting but I solved the problem. After getting home, I immediately rechecked the bolts and disassembled the crank and boy oh boy, found out that I put the inner chainring the other way around. In my excitement when installing the new chainring, I didn't realize that I'd put it the wrong way and also didn't realize anything weird during my ride because I haven't actually used the 34T ring yet.

So, my stupidity costed me a bit of paint on my chainstay that I ended up covering with electrical tape, but all good now.

| improve this answer | |
  • That hat been my second guess, after the bolts. I had 'succeeded' in doing the same! – Carel Apr 1 at 18:28

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