Mechanical considerations in changing the cassette
 

There are a couple of hills in the areas that I ride which literally put me to the brink of O2 starvation. Yes I could train more but.... I was considering changing the cassette from my current 11/28 to a 11/32 (leaving the crank set the same). I have a compact crank set at 50/34.

Are there any mechanical considerations that need to be taken care of when moving to a larger cassette e.g. like derailleur cage length etc? Or is it a simple plug and play of a new cassette? I currently have an Ultegra 6800 group on the bike.

Will moving to 11/32 make much difference climbing the hill?

Thanks in advance.

Short cage or long?
Short cage handles exactly what you currently have.
Long cage will handle exactly what you want.
Both max cog size and total chain wrap.

EDIT- I would venture to guess, you have a short cage.
Shimano is somewhat conservative in their ratings, but a 4T larger big cog may be a bit too much. It might be doable, but there are too many variables including RDER hangar geometry to tell until you try. If you have the GS version (longer cage) you would still need a longer chain.

If you are barely making it up the hill now, 4T more will be a godsend.

Going to a larger cassette always calls for checking that you have adequate chain length.

A large number of mechanics fit chains based on big/big+1", which is the minimum acceptable length. If so, then there's no upside room, and you risk destroying your drive train if you shift into the new big/big combination.

So, making sure the chain is long enough, or replacing it is the first and most critical step.

The other consideration is RD take up capacity. (big+big - small+small). The added 4 teeth may take you beyond the rated capacity. However that's not as critical. If you measure the chain based on big/big, then the only issue may be that the RD can't take up the slack using the smaller chainring with the smallest few rear sprockets. You don't likely use those combinations, and no harm will come if you shift into them.

To answer the part about a difference in hill climbing. Yes most all will notice the easier (by 4 out of 28 or about 14%) effort. Now it will take more crank strokes to get up the hill as each travels less far forward. So either about a 14% faster spin to maintain the same speed, or for the same cadence about 14% slower a pace.


I climbed Old Tahoe Pass in a 34 front and 32 rear combo. Did I want a lower gear, yes, did I make it up with out issue, yes. Andy