Less than one year old bike. How to mitigate the damage? What do I do wrong? by TheTphs Bicycling Bike Bike Repair Biking Cycling Repair
LamimaGC on February 21, 2026 1:00 pm This is called chainsuck – could be reduced by changing the derailleur to a type that has some type of damping.
weeddee85 on February 21, 2026 1:01 pm You need a spacer between the frame and the bearing cup to push it out so the crack isn’t hitting the frame
Turbulent_Deal_3145 on February 21, 2026 1:59 pm That happened from your chain getting sucked in between the rings and frame. Not uncommon and not *really* a problem in itself.
TheDaysComeAndGone on February 21, 2026 2:08 pm Several possible sources: Too big chainring, missing spacer(s) for the bottom bracket bearings, loose/broken bearings, chainsuck …
irregular-bananas on February 21, 2026 2:34 pm My sons trek marlin was that way from the front derailleur being out of alignment and indexing the chain to far, making it come off easily.
6 Comments
This is called chainsuck – could be reduced by changing the derailleur to a type that has some type of damping.
You need a spacer between the frame and the bearing cup to push it out so the crack isn’t hitting the frame
That happened from your chain getting sucked in between the rings and frame. Not uncommon and not *really* a problem in itself.
Several possible sources: Too big chainring, missing spacer(s) for the bottom bracket bearings, loose/broken bearings, chainsuck …
My sons trek marlin was that way from the front derailleur being out of alignment and indexing the chain to far, making it come off easily.
Keeping your drivetrain clean helps prevent it too