Bicycle Mechanics - Changing a cassette

I would like to replace my cassette with a larger one. What all is involved? Do I have to get another chain? What sort of adjustments have to be made? Is it an easy swap? Have an Ultegra set up with a compact crank on a Cannondale.
thanks!

First thing you could do is search this forum ....... But if that is too difficult, just go to www,parktool.com for all your answers.

Define how MUCH larger.
Larger cogs may entail a different RDER, depending on what you currently have.
You probably will need a longer chain.
What do you currently have and what do you want to go to?

All depends on how much of a change you're talking about.

Define how MUCH larger.
Larger cogs may entail a different RDER, depending on what you currently have.
You probably will need a longer chain.
What do you currently have and what do you want to go to?

12-23 is what's on it. Think that a 27 may be the ticket. Would that make a considerable difference?

12-23 is what's on it. Think that a 27 may be the ticket. Would that make a considerable difference?

That's a fairly big change but may not require a longer chain. Put the new cassette on, on a work stand try shifting gently into the big chainring/big cog combination. Check to make sure the rear derailleur has not reached its maximum forward travel (bottomed out). Good to go.
While you're at it check the chain for stretch with a good steel ruler. A 24 pin interval of new chain will be exactly 12 inches in length. When any 24 pin interval measures 12 1/16th inches you need a new chain.

Al

That's a fairly big change but may not require a longer chain. Put the new cassette on, on a work stand try shifting gently into the big chainring/big cog combination. Check to make sure the rear derailleur has not reached its maximum forward travel (bottomed out). Good to go.
While you're at it check the chain for stretch with a good steel ruler. A 24 pin interval of new chain will be exactly 12 inches in length. When any 24 pin interval measures 12 1/16th inches you need a new chain.

Al

Hi Al,
Do you think a 25 would suffice? Would just a coupla extra teeth make that much difference?

Unless the chain was sized too short to begin with a 27 should work fine. Now keep in mind an older worn chain with a new cassette may cause compatibility issues due to uneven wear. Try it and see, might have to replace the chain as well.

When you lengthen a chain, you do it with an inner & outer link, aka a link SET. ONE link SET is good for a 4T increase on the largest rear cog.
When properly sizing a chain, you should have 1 link SET + any fraction of a link SET extra. Therefore, you may have anywhere between 1.0001- 1.9999 link sets of "slop".
It kind of depends on how large your "fraction" of a link set is...
IF you are getting a new cassette, it may be a good time for a new chain anyway, depending on how much use the current one has.
If you bought the lock ring tool and made/bought a chain whip, you could easily swap them back and forth for different riding conditions. The you could keep your old, properly sized chain, for use with your old cassette, although the slightly longer new chain shouldn't present a problem.