Look at this. The spokes behind the cassette of my MTB are all scratched and bent. How might this have happened? The back of the cassette has no scratch at all.
Asked
Active
Viewed 767 times
3
-
2that was caused by the chain getting stuck between spokes and cassette. – Burki Aug 30 '23 at 10:15
-
1@Burki that is an answer, not a comment ;) – Rеnаud Aug 30 '23 at 10:24
-
@Renaud You are right. I was too lazy to give a little more background, at first :-) – Burki Aug 30 '23 at 10:28
-
I didn't do it. It must be the previous owner. One should carefully inspect a bike when buying second hand. – Ender Aug 30 '23 at 10:32
-
1A side note: I'd recommend checking that brake rotor. From what little we can see it might be close to or beyond it's limits. – Burki Aug 30 '23 at 10:36
-
How do you know that? – Ender Aug 30 '23 at 11:09
-
1From the discoloring, and from the appearance of a visible step in the brake surface. Typically, the thickness of a new brake disk is 2mm, and the minimum width is 1.5mm. So, signs of wear like what can be guessed here are at minimum a reason to get the calipers out – Burki Aug 30 '23 at 16:19
-
1I posted a link to this old question of mine under the answer, but it's worth putting here too. It addresses the repair. – Chris H Aug 30 '23 at 19:20
2 Answers
15
This kind of damage occurs when the chain gets stuck between the cassette and the spokes. It happened while riding, most likely, as indicated by the fact that the spokes are bent in the pull direction of the chain.
This kind of damage can be (mostly) avoided by making sure the limit screws of your rear derailleur are set correctly, and even more by adding a protective disc (a roundish piece of plastic typically clipped on the spokes, that would in turn take the impact should the chain get there again)
As @DoNuT mentions in the comments, the spokes are done for, at least from a fairly professional standpoint. I'd still like to point out that i have seen and ridden a number of bikes with similar damage to the spokes, that still lived for at least hundreds of kilometers, so i would not consider this damage a major security risk. Just make sure to check them regularly, and after the fist spoke snaps, don't wait any longer.
-
3I guess it would be worth adding that the spokes are probably trash and ask for a replacement too, right? ;) – DoNuT Aug 30 '23 at 10:30
-
1Indeed, I have also seen spokes with a similar damage to work for a long time. – Vladimir F Героям слава Aug 30 '23 at 12:50
-
1When I got something caught in my derailleur, the plastic disc shattered and the chain got quite stuck between the cassette and spokes. The spokes were only a little more chewed up than this and two snapped between 70 and 130km later. – Chris H Aug 30 '23 at 15:54
-
@ChrisH agreed, that can happen. But would you say it was a security risk? – Burki Aug 30 '23 at 16:20
-
-
1@Burki the plastic disc didn't make things worse, but it didn't help either. It can help if the limit screw becomes badly adjusted. Breaking spokes are definitely a safety issue for a few reasons. One snagged my chain, locking up the back wheel. I unclipped in time to get my foot down and there was no traffic. The wheel deforming can also jam it into rim brakes. Getting stranded is a safety issue if you ride long distances in all weathers, as I do. BTW I assumed you meant "safety" not "security". English makes a distinction that other languages I know don't routinely – Chris H Aug 30 '23 at 19:18
-
1@Chris thank you, yes, i meant safety. And thanks for pointing out the risks! – Burki Aug 31 '23 at 04:22
0
Creo que la falta de mantenimiento y saver usar los camvios de velosidad, revisar vien los ajustes del rotor.
I think the lack of maintenance and knowing how to use the speed changes, check the rotor adjustments.
-
1Welcome to Bicycles SE. Could you repost your answer in English please? – Ted Hohl Aug 31 '23 at 00:05
-
Welcome to the site - could you please use [edit] to expand your answer with more into? – Criggie Aug 31 '23 at 00:44