Can I get some advice from the cyclists please?

[JasonM]

My lad has managed to smashed his derailleur gear thingy, 'It just broke' of course it did..... I don't know much about bikes, I can change a tyre, brakes and even done a chain but Im not au fait about these, Ive never needed to replace one. My question is, do I need like for like? I get that a 6/7 speed is needed was thats whats on the old one, are these all the same in principle? Doing a search for Shimano Tourney brings up lots, I guess its a range, what should I be looking for? Any pitfalls I might encounter?
Many thanks in advance.
Jase

[spuds]

'It just broke' of course it did.....
Jase

I have nothing to offer mate other than another Father's empathy....

[JasonM]

Cheers Spuds, empathy is good to have too.
Bloody kids....

[markc]

Oddly that is a 6/7 speed tourney (like this one: https://www.amazon.co.uk/SHIMANO-Rea...3924206&sr=8-2)

I say oddly as you quite clearly have a 8 speed cassette on there and by rights should need one of these: https://www.amazon.co.uk/SHIMANO-Tou...3924206&sr=8-3

What gear levers (or twist grips, etc.) are on the bike? That will give a better idea of what you need.

Cheers,

Mark

[JasonM]

Thanks Marc.

[markc]

Right, those gear shifters will work with either of the derailleur I posted as they are 7 speed and the derailleurs are 6/7 speed in the first case and 7/8 speed for the second. However, your son will not have been able to use the full range of gears on his bike (and I suspect there might have been an adjustment issue as well, symptom clattering/clicking gears).

I’d probably go with the 8 speed version as it will allow you to buy an 8 speed shifter in the future and give you all the gears that you should have.

Note that setting up indexed gears can be a bit of a faff and you’ll want to watch a youtube video or two if you’re doing it yourself. You’ll also need a new cable as the old one is knackered.

My advice would be, take it to your local bike shop and ask them to fix it. They won’t overcharge you and you’ll be sure that it’s good when you’re done. My suspicion would be that they will recommend new chain, chainrings and cassette as well - depending on wear, but they might not, it’s hard to tell from a photo.

Cheers,

Mark

[JasonM]

Thanks Marc, Ill do that, I really appreciate your advice.

[cbh]

Obviously you will need a new rear derailleur, (https://www.decathlon.co.uk/p/rear-d..._/R-p-X8523798) and a new gear cable, and as you will need to thread the chain through the derailleur, you will need to either split the chain and then rejoin or buy a new chain. It will need the high/low limit screws setting along with having to index the derailleur to make it shift correctly.

It's not a difficult job and there are loads of videos on Youtube if you fancy doing it yourself or your local bike shop can do it in about 45mins!

[JasonM]

Thank you, Ill probably let a pro do it as Marc suggests, Ive no doubt I could sort of do it, but it would take three times as long, be half as good and stress me out a bit.
I do like having a go at most things though, but sometimes a pro is there for a reason.

[Craig]

I've never had to replace a derailleur but with 5 bikes in the garage and 2 kids who inevitably seem to bash their bikes up, I decided it was time to learn how to adjust one. This was the best you tube video I found:

https://youtu.be/36YFI637EZs

Good luck, at least a bashed up bike means it is getting used and not just gathering dust!

[wileeeeeey]

Park Tool have an excellent YouTube channel. Worth a look.

https://youtu.be/TPhsSTR5ybw

[Captain Morgan]

Thank you, Ill probably let a pro do it as Marc suggests, Ive no doubt I could sort of do it, but it would take three times as long, be half as good and stress me out a bit.
I do like having a go at most things though, but sometimes a pro is there for a reason.

To be honest changing a older derailleurs is fairly painless, replacing the cable is much like replacing a brake cable and setting the high and low travel range is simply adjusting two screws set the b-screw and then it’s just working on indexing via the barrel adjuster. Sounds much more complex than it is and the older lower speed mechs are more accommodating.

Take a look at the park tool videos:
https://www.youtube.com/watch?v=B37TW_YVC8E&vl=en

[Si]

I think this appears to be the correct model (or at least the model you have on there, with its “directional pulley”):

https://www.amazon.co.uk/SHIMANO-Uni.../dp/B01DQ8KA8O

Somewhere on the parallelogram bits there will be a model number, to be sure.

If it has had a knock hard enough to damage it, the chances are that the derailleur hanger, where it mounts to the frame, could have been knocked out of alignment. If that is the case, you’ll never get the new one set up right until that is realigned. That is also easily sorted but needs either a proper derailleur hanger alignment tool or a home made version of same.

So both jobs (alignment of hanger, and fitting / setting up the derailleur) are pretty straightforward but made much easier with a the alignment tool and a bike stand. If you don’t have those it might be more time efficient for you to let the bike shop do it.

[higham5]

I think this appears to be the correct model (or at least the model you have on there, with its “directional pulley”):

https://www.amazon.co.uk/SHIMANO-Uni.../dp/B01DQ8KA8O

Somewhere on the parallelogram bits there will be a model number, to be sure.

If it has had a knock hard enough to damage it, the chances are that the derailleur hanger, where it mounts to the frame, could have been knocked out of alignment. If that is the case, you’ll never get the new one set up right until that is realigned. That is also easily sorted but needs either a proper derailleur hanger alignment tool or a home made version of same.

So both jobs (alignment of hanger, and fitting / setting up the derailleur) are pretty straightforward but made much easier with a the alignment tool and a bike stand. If you don’t have those it might be more time efficient for you to let the bike shop do it.

100% good advice above. I have 5 bikes 2 mtb 2 road and a gravel bike. Last summer I struggled with indexing / chain jumping on one bike. In the end I gave up and I took it to my local bike shop. Bent derailleur hanger sir £11.

Prior to this I bought a new chain and new rear cassette eg £50 trying to solve the indexing problem!

Steve

[JasonM]

Thanks guys, I appreciate it.