Double to a Triple?

Scott has a double chain set and wants to change to a triple chain set; his question is whether he will need to change the bottom bracket for the triple. We think he probably will and maybe some other bits too, we give him our thoughts and another recommendation that could save him a lot of money and problems!

Question:
I currently run a twin gear on my front derailleur but want to put a three on will I have to change the bottom bracket?

Hi Scott,

It is very likely you will need to change the bottom bracket as the triple is a chain ring wider, your other problems could be that you will need a new front and rear derailleur. The front derailleur has to be slightly wider to take the difference in angle of the chain, the rear derailleur may also need to have a longer arm to take up the extra lose chain that you will have with difference of chain ring size as you will probably be fitting a 30/40/50 triple, so that is a difference of 20 teeth from the small to the large chain rings.

What might be a good alternative could be to fit a compact double chain set with something like 34/50 teeth chain rings, your bottom bracket and front derailleur should manage a compact, your only problem could be the rear derailleur, but normally that should be OK too. I hope this points you in the right direction?