Cassette ring 'swop'

[Macka]

Hi,
May be a daft question....
Have a 12-25 cassette (9 speed Shimano) at the moment...would it be possible to just swap out the last or maybe the last two cogs for larger ones (i.e. the 23 to 24 and the 25 to 27)??
Rather than buying a complete new cassette?
Cheers
Steve

 

[Globalti]

Er... where would you buy the two bigger rings?

Yes you could do it but it would produce a bit of a jump in the ratios.

 

[Macka]

Er... where would you buy the two bigger rings?

From other cassettes I have lying around really....
I guess I should just give it a go, can always revert back!

 

[mickle]

Perfectly feasable - if the rear mach capacity isn't compromised etc - though you might lose some shift quality.

 

[andrew_s]

separate sprockets are available from rosebikes
There are multiple versions of each size, identified by code letters. For best shifting you've got to use the correct version so that the ramps and gates line up properly. Sheldon may have a page on it.

 

[Broadside]

I don't think you can do this (someone correct me if I'm wrong), but the largest 5 sprockets are riveted together. You could swap out the smallest 4 sprockets but not the largest unless you are going to drill the rivets or prise them apart.

 

[threefingerjoe]

Yes, drilling out the rivits is exactly what you have to do, and it's not a major problem. However, rather than screwing up the ranges by making a big jump in the largest 2 gears, why not consider giving up the 12 tooth gear for a larger gear, for example, making it a 13 or 14-27? OR, it may be even easier to drop to a slightly smaller chain ring and leave the cassette alone.

 

[Macka]

Thanks for the info everybody, very interesting and great advice
May go for dropping a 12 and slipping a 27 at the top end...

 

[Macka]

Sorted this out yesterday...
Got an old MTB cassette and drilled out the rivet head and prized the sprockets apart. Took out the 28 and spacer and fitted it to the back of the original cassette. Took out one of the smaller rings and re-fitted.
Re-adjusted the rear mech, indexing etc and all works splendidly, in fact it's smoother and better set-up than ever.
Thanks for all the advice..

 

[andrew_s]

I don't think you can do this (someone correct me if I'm wrong), but the largest 5 sprockets are riveted together. You could swap out the smallest 4 sprockets but not the largest unless you are going to drill the rivets or prise them apart.

Drilling out the rivets may be indeed required, though some cassettes use thin screws instead.
What is a problem is that the more up-market cassettes have the sprockets mounted in groups of 3 or so on an aluminium carrier, rather than just fitting direct to the freehub. All you can do here is to get a cheaper cassette, or buy all the sprockets plus spacers.

 

[ColinJ]

However, rather than screwing up the ranges by making a big jump in the largest 2 gears, why not consider giving up the 12 tooth gear for a larger gear, for example, making it a 13 or 14-27?

On my 9-speed Campagnolo-equipped Basso, I did just that.

I live in a very hilly area and decided that being able to ride up 20-25% climbs was more important to me than being able to pedal downhill at 40+ mph so I switched from a 12-23 cassette to a 13-26 and eventually to my current 14-28.

I pedal up to 35 mph on descents and beyond that I get into an aero tuck and freewheel. I can still hit 50 mph at times but no longer feel the need to try and do 60!

 

[Zoiders]

Not all cassettes are riveted, if it's good enough quality it will come apart with a 2mm allen key as the pins are threaded.