Re: Had a wtf? this morning - Ping AMuzi

On 2/22/2025 4:21 PM, Roger Merriman wrote:

Shadow <Sh@dow.br> wrote:

Went out for my morning ride. Just before a rather steep hill changed
down and I heard a clump and the chain jammed.
>
I looked back and half of my rear derailleur was sitting on the
asphalt.
>
OMG, I thought to myself, this is almost as embarrassing as a crank
arm falling off. Then faced the "walk of shame" home.
>
Note, I scrub chain/jockey wheels/sprockets with water and detergent
every 200 Km. Was almost due for a new clean. Gear change was
absolutely smooth until the incident. HI and LOW screws perfect, no
way the chain came off and "fell into the spokes".
>
Note I managed to rip a spoke clear out of the wheel with the
breakage. What fell into the spokes was half the derailleur. I suppose
that'll mean a new wheel too
>
:(
>
<https://www.sendspace.com/filegroup/v/qdHDWfYEJvo99L3/MhFp6hhZL5Z8ugxHfSuN/uTo4>
>
The "cleaned" in the filename is because I cleaned the EXIF metadata,
not the parts after the incident....
>
So "wtf" happened, what did I do wrong and how can I prevent it from
happening again?
>
TIA

 Did the derailleur come apart due to impact with wheel/cassette or a
failure and then do so?
 My old commute bike, had a rear mech fail where the cage and parallel meet
apparently was glued in place? Was an Alivio so broadly similar to the
Tourney I think from memory, Cues which I replaced it with is substantially
more heavily built like the MTB mech’s as to if it will last any longer?
 The Alivio lasted 9 years and 19,000 miles so probably got my moneys worth!
 Mind talking of Andrew I expressed surprise that front mech’s could wear
though! My Gravel bike front mech (Sora) had to be replaced due to that!
Only just shy of 12,000 and 7ish years old so definitely sub par, though
have replaced like with like and didn’t really seem any reason to match the
rest of the bike ie GRX mostly with Tiagra shifters.
 Okay (at least in uk) neither of Tourney/Alivio/Sora/Cues are particularly
expensive being £30ish for a derailleur.
 Roger Merriman

Unclear but the usual failure is a worn or bent or twisted or not quite well adjusted rear changer.
The normal couple of millimeters between cage and spokes is just enough to clear but once any of the above occur and the cage engages a spoke, the bike+rider mass at whatever speed yanks that changer up and over the axle until one or more things either break or jam the wheel to a skid stop.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971