Chainrings, Cassette & derailleur MTB

[Bagheera]

Hi folks,

I posted a week or so ago and got some great help as I'm stripping down and refreshing my old Apollo mountain bike mainly to learn mechanical skills and have an off roader. My Giant Hybrid bike is ordered and shoukd be with me soon! I just have a few questions from today's work:-

The Chainrings (Crank/Chainset not sure on terminology), do you replace as a whole or the individual rings? Mine has 3 main rings but apart from the plastic protective piece doesn't appear to come apart.

Should you replace the Cassette when you replace the chainring? The chain rings are bent, rusty but the cassette seems better but I'm no expert!

On the derailleur. Do you replace the whole thing or just the indivdual cogs? There's a metal bracket and little screws attached, just wondered if the lot gets changed?

After all the above, should i really fit a new chain too?

Many thnks in advance for any replies.

 

[Hugh Manatee]

Some low end chainsets, (that's the crank and the rings) don't come apart. Higher end stuff you can replace individual chainrings.
Anything with a sort of shark fin profile, (teeth on cassette and rings) is worn and will struggle to integrate with newer components.

 

[Bagheera]

Some low end chainsets, (that's the crank and the rings) don't come apart. Higher end stuff you can replace individual chainrings.
Anything with a sort of shark fin profile, (teeth on cassette and rings) is worn and will struggle to integrate with newer components.

Thanks for replying.

I can't honestly say the cassette are fin like, they are pretty straight at the top. However, a couple appear twisted so don't know whether that would qualify for replacement of whole cassette?

 

[vickster]

Thanks for replying.

I can't honestly say the cassette are fin like, they are pretty straight at the top. However, a couple appear twisted so don't know whether that would qualify for replacement of whole cassette?

Post some photos 👍

 

[Bagheera]

Attached a couple of photos . Cheers guys!

 

[tom73]

That chainset is one piece so will need the whole thing replacing I'd replace the cassette at the same time.
You may as well replace the chain.
That way you start a fresh and learn how to do we whole thing at the same time.

 

[fossyant]

Weeps..... 😭

 

[Bagheera]

I'm just browsing parts on Halfords/Wiggle. Now the Cassette on mine has 7 sprockets. The Chainset I'm looking at is a Shimano triple '9speed'....are these compatible? Could someone just briefly explain compatibility of chainsets & cassettes?

What 'speed' is my bike? 3 on the crankset and 7 at the cassette currently..... I've read a few articles but am still a bit confused!

 

[tom73]

Total number at the front x total number at the back
So yours is 3x7 so 21 speed.

 

[Ajax Bay]

On the derailleur. Do you replace the whole thing or just the indivdual cogs? There's a metal bracket and little screws attached, just wondered if the lot gets changed?

The rear derailleur (RD) comes in one 'piece'. The 11t jockey wheels will need cleaning and greasing - they can be removed using an allen key. They could be replaced but I doubt they need to be (replace when teeth are getting 'sharp'). And make sure the top goes back in the top (etc).
The metal bracket attached by screw(s) to the frame onto which the RD screws (again an allen key) is called a hanger. Only change that if it's bent out of vertical.

I can't honestly say the cassette are fin like, they are pretty straight at the top. However, a couple appear twisted so don't know whether that would qualify for replacement of whole cassette?

I'd say the cassette was little used (the twisted teeth are meant to be like that to help shifting), and likely the chain will have the same low level of use. Give the sprockets and chain a good clean and then a good oil and wipe and oil and wipe.
I think that it's likely the sprockets (7 speed) are actually not a cassette but a freewheel. A picture with the wheel out of the sprockets will tell you/us. https://sheldonbrown.com/freewheels.html

Get a cheap replacement for the chainset (?£15 or less used - very likely to be square taper and 170mm cranks) (possible links below - think your large ring is a 42). And ride.
Shimano-Crankset-FC-TY501-square-6-7-8-speed-170-mm-42-34-24-teeth-black
https://www.ebay.co.uk/p/1990246613?iid=142137264556
HTH

 

[tom73]

Youtube is a great place to start with repair stuff
if in doubt start with park tool clips.
They also have a handy repair help blog inc links to the clips.
https://www.parktool.com/blog/repair-help/?query=

 

[Ajax Bay]

What 'speed' is my bike? 3 on the crankset and 7 at the cassette

Halfords (and @tom73 ) would describe it as a 27 speed .
It is a 7 speed drivetrain (shifter/RD/sprocketsx7) with a triple chainset (three rings) so most usefully described as 3x7 (cf 1x11, 2x10 etc).

 

[tom73]

Point being ?
Oh yes smart arse

 

[Ajax Bay]

Point being the OP needs to look for 7 speed components: they certainly haven't got your depth of knowledge. Changed your chain this year yet?

 

[Bagheera]

Halfords (and @tom73 ) would describe it as a 27 speed .
It is a 7 speed drivetrain (shifter/RD/sprocketsx7) with a triple chainset (three rings) so most usefully described as 3x7 (cf 1x11, 2x10 etc).

So the '9 speed' shimano chainset I saw on wiggle for example, would that be compatible with a 7 speed cassette/freewheel? Once I've taken the wheel out I'll post a photo and of the jockey/idler wheels....

Is there anything wrong with using the exisiting LH crank arm? Or generally would you fit a new LH arm with a chainset replacement? I see the ebay one come with a new LH arm but don't think the wiggle one does.

Thanks for all the replies, it's really helping me get my head round this stuff!