Originally Posted by
urbanknight
If you currently have a triple, you probably already have a long cage derailleur which should cover a 32. You might have to lengthen the chain, but that should be it.
If it's a road rear derailleur, no matter if it's a short or long cage, it may not allow a 32T cog.
Shimano specifies a maximum rear cog of 27T for it's road rear derailleurs. Experience says 30T will usually be ok and 32 is very iffy depending on the configuration of the derailleur hanger. A MTB rd is certain to work.