It doesn’t “just happen” but it is something that is designed to occur in order to save the frame in the event of an incident.
The derailleur hanger has broken. It is a sacrificial part that prevents the frame from being damaged should the derailleur be struck or get caught in the wheel due to poor limit screw adjustment. If you’re very lucky, the rear derailleur is also still functional.
You’d need a new derailleur hanger to fix it, and potentially a new rear derailleur if it too was damaged.
Intrepid00 on
He could have hit something sticking out of the ground that caught it but the chain and gear set look dirty and sticky. If the links get sticky enough I’ve had it get tangled and if he was really peddling brake it. I’ve done that.
Start teaching him how to maintain the chain and gear set by cleaning it with him.
GoesUp on
The derailleur was poorly adjusted and probably a little bent
MagicManTX84 on
My wife bent her derailleur hanger a year and a half ago. Bike shop replaced it for like $50. Luckily, the derailleur itself wasn’t damaged. She had trouble shifting and we noticed it. This derailleur looks it might need replacing. Just get a better one if you can. Was it a Shimano Tourney?
SiBloGaming on
either the limit screws were off, or something that got kicked up like a small rock or a stick hit the RD and pushed it into the spokes. Either way, you will need a new RD hanger and likely a new RD.
No_Solid_2667 on
Limit screws not set properly is my best guess. Chain went into the wheel and resulted in what you see here. That’s why they have the dork disc plastic covers behind the cassette to prevent something like this from happening I gather.
Cougie_UK on
Gears out of alignment or the rear mech has been bent out of shape and towards the wheel. Has the bike been dropped gear side down on the ground ?
He’s gone to put the bike into the lowest gear – big sprocket and the rear mech has hit the spokes and been ripped off. You should see some marks on the spokes I’d think.
manjiss1 on
This happened to me. I was riding through traffic and wanted to overcome a truck, so I thought I’d speed up… When I stood on the pedal to pedal stronger, the derailleur just gave up and crumbled up, almost making me fall, had to carry the bike and call a cab. Your son may be telling the truth.
slackshack on
Probably shifting [poorly] under load, the hanger worked and failed the way it is designed to. buy two replacements when you find the right one.
PeevedValentine on
It does “just happen”, as in it will have snapped quickly and spectacularly, but it’s caused by being dropped on the floor repeatedly on the same side as the derailleur.
There will be evidence of other damage on the end of the handlebars and pedals to coincide with this.
He needs to look after his bike better.
laney_deschutes on
It does just happen if a stick gets caught in your chain or the derailer hasn’t been adjusted properly
Independence_1991 on
Simple answer, yes it can and does happen.
stranger_trails on
This can be a Just Riding Along (JRA) however the cause of this happening would have been from the bike falling on the hanger side, catching a rock, getting bashed in a bike rack – something to offset the gears inwards and then catch a spike while riding.
Looks like a super common hanger shape – I believe Wheels Mfg #25 or maybe #27 – lots of brands use these two and you can usually find cast factory ones cheaper however they are softer in my experience. Derailleur looks to be Altus M310 (~$40 CAD) and looks like the chain is also pretty twisted (~$20 CAD)
PippinCat01 on
Same exact thing happened to me with the same derailuer before. Either a bump or stick pushed it a few mm towards the spokes and it caught. It’s a cheap derailuer, $20 and change or so in pre covid pricing.
Justcruisingthrulife on
Can, first ride on a new mountain bike and a stick flicked up into the rear derailleur and it tore off.
finverse_square on
Looks like chain shifted into spokes and wheel sucked up and ate derailleur. Can absolutely “just happen” if it’s adjusted wrong. Can also be the result of a big hit to the derailleur, in a crash for example.
Impossible to know now, but his story isn’t unreasonable
Asleep-Ad1723 on
That exact thing happened to me. I’m just peddling then halted to a stop. I don’t know why my derailer whipped up into my spokes. New derailer fixed that.
manual-override on
This happened to me. My hanger got bent and I stupidly kept riding. An expensive lesson.
18 Comments
It doesn’t “just happen” but it is something that is designed to occur in order to save the frame in the event of an incident.
The derailleur hanger has broken. It is a sacrificial part that prevents the frame from being damaged should the derailleur be struck or get caught in the wheel due to poor limit screw adjustment. If you’re very lucky, the rear derailleur is also still functional.
You’d need a new derailleur hanger to fix it, and potentially a new rear derailleur if it too was damaged.
He could have hit something sticking out of the ground that caught it but the chain and gear set look dirty and sticky. If the links get sticky enough I’ve had it get tangled and if he was really peddling brake it. I’ve done that.
Start teaching him how to maintain the chain and gear set by cleaning it with him.
The derailleur was poorly adjusted and probably a little bent
My wife bent her derailleur hanger a year and a half ago. Bike shop replaced it for like $50. Luckily, the derailleur itself wasn’t damaged. She had trouble shifting and we noticed it. This derailleur looks it might need replacing. Just get a better one if you can. Was it a Shimano Tourney?
either the limit screws were off, or something that got kicked up like a small rock or a stick hit the RD and pushed it into the spokes. Either way, you will need a new RD hanger and likely a new RD.
Limit screws not set properly is my best guess. Chain went into the wheel and resulted in what you see here. That’s why they have the dork disc plastic covers behind the cassette to prevent something like this from happening I gather.
Gears out of alignment or the rear mech has been bent out of shape and towards the wheel. Has the bike been dropped gear side down on the ground ?
He’s gone to put the bike into the lowest gear – big sprocket and the rear mech has hit the spokes and been ripped off. You should see some marks on the spokes I’d think.
This happened to me. I was riding through traffic and wanted to overcome a truck, so I thought I’d speed up… When I stood on the pedal to pedal stronger, the derailleur just gave up and crumbled up, almost making me fall, had to carry the bike and call a cab. Your son may be telling the truth.
Probably shifting [poorly] under load, the hanger worked and failed the way it is designed to. buy two replacements when you find the right one.
It does “just happen”, as in it will have snapped quickly and spectacularly, but it’s caused by being dropped on the floor repeatedly on the same side as the derailleur.
There will be evidence of other damage on the end of the handlebars and pedals to coincide with this.
He needs to look after his bike better.
It does just happen if a stick gets caught in your chain or the derailer hasn’t been adjusted properly
Simple answer, yes it can and does happen.
This can be a Just Riding Along (JRA) however the cause of this happening would have been from the bike falling on the hanger side, catching a rock, getting bashed in a bike rack – something to offset the gears inwards and then catch a spike while riding.
Looks like a super common hanger shape – I believe Wheels Mfg #25 or maybe #27 – lots of brands use these two and you can usually find cast factory ones cheaper however they are softer in my experience. Derailleur looks to be Altus M310 (~$40 CAD) and looks like the chain is also pretty twisted (~$20 CAD)
Same exact thing happened to me with the same derailuer before. Either a bump or stick pushed it a few mm towards the spokes and it caught. It’s a cheap derailuer, $20 and change or so in pre covid pricing.
Can, first ride on a new mountain bike and a stick flicked up into the rear derailleur and it tore off.
Looks like chain shifted into spokes and wheel sucked up and ate derailleur. Can absolutely “just happen” if it’s adjusted wrong. Can also be the result of a big hit to the derailleur, in a crash for example.
Impossible to know now, but his story isn’t unreasonable
That exact thing happened to me. I’m just peddling then halted to a stop. I don’t know why my derailer whipped up into my spokes. New derailer fixed that.
This happened to me. My hanger got bent and I stupidly kept riding. An expensive lesson.