alig said:The reason for swapping cranksets is because I'm looking to upgrade to a 53T
I just bought a 105 double (5502)
Once I sort out the chain line issue by getting the right BB length, will I then be able to switch from a long cage (sora) to a short cage 105? This way I can get a few links back in the chain that I'll be losing to the extra 3T
Well, back to part of your original question, you do not need to change your derailleurs other than for cosmetic reasons, for the most part ...
And, you have it backwards as far as "get(ting) a few links back" because you will ultimately shorten your chain if you switch to a short cage rear derailleur.
Personally, I would ALWAYS rather have a medium-or-long cage rear derailleur because you can shorten a chain on the road more easily than you can add links (which won't exist).
N.B. As great a value as 105 components are, the cost differential between the Octalink 105 & Ultegra is so minimal as to make it worth the small amount of difference to opt for the Ultegra.
In addition to being a few grams lighter & having a marginally better finish than the 105 rear deralleur, the Ultegra rear derilleur has much better pulleys; and, the pulleys are worth more than the difference in the price of the two derailleurs.
So, it's too bad you already got your 105 crank for the fore mentioned reason ...
The bottom line is that you do NOT need to change the derailleurs unless you want to for cosmetic reasons ... if you are racing and/or logging 100+ miles per day, then there is a benefit to NOT dragging around a few extra links of chain.
BTW. You could have simply bought a 53t chainring, separately.