Road Cycling - Newbie with questions on rear cassette

Hey all,

There is a lot of talk on this board about 12-23 this-and-that on the rear cassette. Other numbers are thrown around as well. As a struggling newb, I confess that I have no idea what you are talking about. Nor do I know why someone would want to change the rear cassette.

Would someone mind explaining all this, please? Or, can you point me to a good place that has a clear explanation?

Thanks

12-23 means that the smallest ring on the cassette has 12 teeth. The largest has 23.

52x12 means that the chain is on the 52 cog ring in the front and the 12 in the back.

People change cassettes to suit various riding conditions. Someone living in a really hilly area may use a 12-26 cassette. Someone who lives in Florida probably can get by with a 11-23.

here are a couple of numbers:
- numbers of cogs, or gears in the cassette, these days you will find bikes with 8 or 9 or 10
- 11-21 or 11-23 or 12-etc., etc., is the number o4 teeth of the smallest and the biggest cog. So a 11-23 cassette will have a smallest cog of 11 teeth, and the biggest cog of 23

- another number that is important is the "difference", which is the "biggest - the smallest" ex. on an 11-23 cassette the difference will be 23-11= 12

there are some other numbers which involve the front crank set chain rings..

here is a short description of the the other numbers and why they are important (from the Campagnolo website Q&As)



I would like to see some examples of compatibility calculations for sprocket sets, dérailleurs and crank sets

Let's take a look at a practical example:
Can the Centaur 10s rear derailleur be used with the 13-29 sprocket set and the 39-53 crank set?
The description of the Centaur 10s rear derailleur reads: minimum sprocket 11, maximum sprocket 29, capacity 30 and maximum front difference 14.
The minimum sprocket and the maximum sprocket are therefore perfectly compatible.
Capacity = (29-13) + (53-39) = 30
Front difference = (53-39) = 14
The Centaur 10s rear derailleur can therefore be used with the 13-29 sprocket set and the 39-53 crank set.

Second practical example:
Can the Centaur 9s rear derailleur be used with the 13-23 sprocket set and the triple 30-40-50 crank set?
The description of the Centaur 9s rear derailleur reads: minimum sprocket 11, maximum sprocket 29, capacity 30 and maximum front difference 14.
The minimum sprocket and the maximum sprocket are therefore compatible.
Capacity = (23-13) + (50-30) = 30
Front difference = (50 –30) = 20
The Centaur 9s rear derailleur cannot therefore accept the maximum front difference of the triple crank set; the Centaur triple 9s rear derailleur should be used, with a maximum front difference of 22 teeth.

Thanks for the responses.

So how does replacing cogs work? Do you buy individual sprockets? Or, do you have to replace the entire set?

For example, I'm using a 12-25 cassette...but if I wanted a 12-27 (which would give me a lower gear, right?), what would have to be done, and at what approximate cost?

Thanks

Yup. Gotta replace the whole cassette. Wide price range depending on what you want. Check around. Here is a good place to start.
http://www.nashbar.com/

Woooaa there Grampy.....

Replacing either the whole cassette, or just some cogs, completely depends on the manufacturer and product. Many cassettes come apart completely, while others don't come apart at all....and to make things interesting some have clusters which can be replaced.

Woooaa there Grampy.....

Replacing either the whole cassette, or just some cogs, completely depends on the manufacturer and product. Many cassettes come apart completely, while others don't come apart at all....and to make things interesting some have clusters which can be replaced.

yeah but usually its makes more sense economically speaking to just change the whole cassette because individual cogs will set you back a lot.

yeah but usually its makes more sense economically speaking to just change the whole cassette because individual cogs will set you back a lot.

I would think this would be particularly true if the cassette has some use already. I don't think I would want to mix new with used.

Philli