When I got Hyro back in 2014, he came equipped with a Shimano Tiagra CS-4600 cassette with a 12-30T gear range. Since then, I’ve put him through his paces, replacing chains as they wear out, but never really changing out the cassette.
Now, 14,700 kilometers later, that changed.
The telltale sign was my Shimano CN-HG54 chain exhibiting 0.5% wear, as indicated by my Park Tool CC-3.2 chain checker. With chains, I err on the conservative side and replace them at the 0.5% mark with fresh ones. It’s vastly cheaper to replace chains, which are the first point of wear, than it is to replace worn drivetrain components.
It just so happened that this is already the cassette’s fourth chain.
It’s not that the CS-4600 cassette is particularly expensive, either, at around PhP900 apiece. Such is the benefit of using steel cogs simply riveted to a center carrier, and avoiding the bragging-rights vanity of lightweight cassettes. At a rated 320 g, this Tiagra unit isn’t going to win any weight weenie awards.
So first, I had to break the old chain…
…then remove the rear wheel and undo the cassette lock ring…
…and finally pull the old cassette from the freehub body.
Fourteen thousand kilometers, eh? I certainly got my money’s worth out of this little mound of sprockets.
Now to slide the new cassette on. It’s also a Tiagra CS-4600 12-30T unit.
On the 12-30T Tiagra cassette, the seven largest cogs (15T, 17T, 19T, 21T, 24T, 27T, and 30T) are all pinned together on a carrier, so they slide onto the freehub body as one unit.
Next goes the only spacer in the entire cassette.
After the spacer comes the 14T cog.
Then the 13T cog goes on. This sprocket has a spacer built in.
Finally the 12T top cog goes on. It also has an integrated spacer, and its face has the teeth that the cassette lockring will bite into.
Grease up the threads on the lockring, spin it on to the freehub body, and tighten to 40 Nm.
Finally it’s time to break out that new chain, resize if necessary, and install it on the bike.
Shimano coats its new chains in a light, sticky grease as corrosion preventive while in storage, and it’s generally okay to use the chain in this condition for the first 100 kilometers or so. With that in mind, I logged a 70-km ride after installing the new cassette and chain, and stripped it of its grease when I got home. That’s a story for another time.