Do I need to change chain length
Looking to swap Tiagra 4600 12-28 to Ultegra 12-30 will this be a straight swap and do I need to adjust change length?
Rear derailleur is Shimano 5701.
Top 25 Contributor
Try putting the chain on the biggest sprocket and the biggest front chainring. If the cage of the derailleur is almost in a straight line with the chain, you may need a longer chain. If the cage/jocky wheels are vertical or at 45 deg, you should have no problem. However it is good practice to fit a new chain when fitting a new cassette (unless your existing cassette has only done a few hundred miles). New chains sometimes "skip" on worn cassettes. You 5701 derailleur should be fine if it is the GS (medium cage) model.