What could cause this?

[VTECMatt]

This is my 16yo Canyon trial bike, on Friday he mentioned he picked up a stone chip but on closer inspection the metal has been sliced into and is peeling back. The photos don t show this.
I m not a biker so have no idea if this is normal, bad luck or something like the chain or cog cutting in. Must have taken some force to do it.

Thanks in advance.

[Harpoon]

I'd suggest chainsuck but do you get that on 1x drivetrains? I remember my Spesh Rockhopper had a big scar on the frame around that spot but that would have had a 3x chainsaw.

[Holdmyhand]

possible rear derailleur lock up with debris and a quick back pedal causing drive side chain to drop and be caught between chainring and stay?

[Scabutz]

Holdmyhand said:

possible rear derailleur lock up with debris and a quick back pedal causing drive side chain to drop and be caught between chainring and stay?

Definitely this. The chain doesn't look very clean or well lubricated. Reckon it's locked and either chain slap on the frame or it's binded and been crunched by the front ring.

WTF is that ugly weld to the left to it though. Has the frame been damaged and repaired (badly)

[VTECMatt]

Bike is 6 weeks old!

[EmailAddress]

He's jumped, or dropped, and pedaled at the point of landing when the chain has slapped.

[VTECMatt]

Thanks for your help, essentially looks like he is pushing the bike a bit too hard and poor technique. I’ll have fun explaining that to him!

[Pickled Piper]

It looks like the chain may have come off the front chain ring and then got jammed against the bike frame.

[VTECMatt]

Thanks for your help, essentially looks like he is pushing the bike a bit too hard and poor technique. I’ll have fun explaining that to him!

[james0]

I’d give him the benefit of doubt, looks like the chain derailed, it happens on MTBs. Some chain rings are better than others at stopping the chain dropping.

A top chain guide will stop that.

A decent chain stay protector isn’t a bad idea either.

Neither have to be expensive.

[Pickled Piper]

You should be pleased your 16 your old is using it. Many teenagers are spending the whole summer playing on video games.

[POIDH]

That is just chain damage - a hardened steel chain hitting an alloy chainstay will do that.

The cheapest and best chainstay protector in my experience is an old inner tube cut open, wrapped round tight, and secure with a zip tie at each end.

[BunkMoreland]

Pickled Piper said:

You should be pleased your 16 your old is using it. Many teenagers are spending the whole summer playing on video games.

That!

A bike without patina is worthless

[VTECMatt]

It is indeed great he gets out, he works on the other days and bought the bike with mostly his own money so proud of him.

Thanks for the inner tube suggestion we did that this evening and ordered a chain guide at the same time.

He definitely enjoys it, got through first set of pads already.

[james0]

Nice one, inner tube works well. it’s fair to say MTB frames can look very used very quickly.

I’ve had a two hour old frame get hit by a rock, thrown up by the front tyre.
It put a nasty dent in the down tube. Was absolutely fine for years after.
Very annoying at the time but purely superficial.

If he’s riding that much the brake pads are worn out already, fair play.

[EmailAddress]

That would be skids lol.

[curvature]

VTECMatt said:

It is indeed great he gets out, he works on the other days and bought the bike with mostly his own money so proud of him.

Thanks for the inner tube suggestion we did that this evening and ordered a chain guide at the same time.

He definitely enjoys it, got through first set of pads already.

Good to see a youngster using a bike.

The other option to the inner tube is self amalgamating tape.