Rear Derailleur replacement

CS10

New Member
Hi all.
Just hoping someone might be able to help.

My son fell off his bike and in the process has bent his rear Derailleur so I need to replace it.

The one on there at the minute is a shimano tourney Rd-ty21a. I've looked but can't find this anywhere.

Can anyone advise me on a suitable replacement?

Thanks in advance 👍
 

si_c

Veteran
Location
Wirral
Shimano Tourney TY-300 should work as a replacement as it's a 6/7 speed rear derailleur. The one that's broken is a few years old I think and no longer available through retail channels but should be compatible with the latest Tourney models as far as I understand it.
 

Cycleops

Legendary Member
Location
Accra, Ghana
If you can post a pic of it from behind the rear wheel we might be able to see if it’s the hanger or the mech itself. Steel or aluminium frame?
 

Cycleops

Legendary Member
Location
Accra, Ghana
Okay I can see now it’s a derailleur with a C shaped direct mount attachment that sits in the dropout. As you have a steel frame there’s no hanger. The Decathlon derailleur should be fine but you’ll need to reuse the C mount which hopefully isn’t bent.
545355
You will need to set the new derailleur up, rather than try to explain its best to follow a video of the process. You might need to unscrew the cage with the small wheels at the bottom of the mech to be able to run the chain through.

View: https://youtu.be/GWRdLIg79Mo
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
You may even get away with straightening the hanger and the 'cage' (where the jockey wheels are) with an adjustable spanner and some care. These mechs are mainly steel so will bend back - not to be done with alloy. Even if it doesn't work, you are looking at £10-£15 for replacement.
 
OP
C

CS10

New Member
It looks to be the actual C shaped mount that is bent. I'm going to try and straighten this.
 

Lovacott

Well-Known Member
It looks to be the actual C shaped mount that is bent. I'm going to try and straighten this.
A long as the chain runs cleanly through the deraileur after you've straightened out the bent bits, you can re-index and re-set the stops.

If you don't have a stand (I don't), you can re-index by slinging a rope or sling around the saddle and hanging the bike from anything overhead so that the rear wheel is a few inches off the ground (I use the space under the stairs and suspend the bike from a stair spindle). Ideally, you need to be able to run the drive train with one hand and make adjustments with the other.

Loads of you tube stuff on indexing and it's well worth having a go. You will understand gearing so much better once you've done it.
 
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