Changing Cassettes

by cjk99   November 4, 2012  

looking at getting a turbo trainer, and thinking about a spare wheel to interchange rather than having to swap tyres.

I currently have a 11-25 on the rear, and am looking at going to 11-30 for the road (to give my knees more assistance) and keep the 11-25 for the turbo wheel.

will i be able to keep the set up the same, or will I need to adjust the chain length and cable tensions?

5 user comments

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You may find that the current chain is too short. If you go up to a 30 then the derailleur may be pulled too far forward if you went for a big at the front, big at the back combo.

You may need to get a new chain and leave more links in it. After fitting the new cassette see how the derailleur hangs with regard to the reference installation instructions.

posted by thereandbackagain [159 posts]
4th November 2012 - 21:14


Your chain probably could do with a few more links but as long as you avoid the big-big crossover gears you could get away without them.

I think the most likely problem you may encounter is whether or not your rear mech can handle a 30t sprocket.


posted by robert.brady [159 posts]
4th November 2012 - 21:15


I'm pretty sure the largest shimano short cage rear mechs can take is a 28t, it will depend what you have and check it on the manufacturers technical section.

posted by kevarino [23 posts]
4th November 2012 - 21:53

1 Like

Depends on the mech. If it doesn't have the capacity, you may find that you jockey wheels ride on the cassette. You can adjust it a little with the adjustment screw that rests on the rear dropout, but I would go with the manufacturers spec. Shimano tech manuals are easily found online - don't know about the others.

Oh and I would be astonished if you didn't need a longer chain, so make sure you factor that in to your costs.

posted by FMOAB [262 posts]
5th November 2012 - 2:38


May I suggest you go for a 11/28 cassette? two teeth less than a 30, but you would probably get away with using the same chain you now have for your 25, tooth cassette; and your deraluer would cope perfectly with a 28, tooth sprocket.

posted by Mostyn [430 posts]
7th November 2012 - 13:10