I normally adopt this technique when tackling hills on my triple Defy 2.5 (30-39-50) (12-25)
Fire it on the 30 and 19. This ratio is roughly the same as the 39 and 25 ratio.
That way if you make it to the top without changing you can be sure that you could have done it in the middle ring. However, it also leaves you that option to move to 21-23-25 if needs be.
Fire it on the 30 and 19. This ratio is roughly the same as the 39 and 25 ratio.
That way if you make it to the top without changing you can be sure that you could have done it in the middle ring. However, it also leaves you that option to move to 21-23-25 if needs be.