I want to swap my Shimano Dura-Ace 11-28 cassette for an 11-40. Or an 11-42. What should I buy to make sure it works well? Thanks! 11-speed

[ladfors]

I want to swap my Shimano Dura-Ace 11-28 cassette for an 11-40. Or an 11-42. What should I buy to make sure it works well? Thanks! 11-speed 2 chainrings

 

[Webbo2]

I want to swap my Shimano Dura-Ace 11-28 cassette for an 11-40. Or an 11-42. What should I buy to make sure it works well? Thanks! 11-speed 2 chainrings

Is your rear mech Dura Ace as well. If so I understand 11 speed DA can only go up to a 30 tooth sprocket.

 

[Sea of vapours]

If your rear derailleur is R9100 Dura Ace then you could use one of these: https://www.wolftoothcomponents.com/products/roadlink-dm

That would move the derailleur back/out a little and enable it to clear the largest sprocket on an 11-40 cassette. Your chain will be slightly too long in small / small, but that's not a huge issue provided you don't actually pedal in it. If possible, find someone who's done this to advise you face-to-face.

 

[Ajax Bay]

To answer this Q properly we need to know what the chainset is eg 50t-34t and what the rear derailleur is including cage type. Measure the distance between the two pulley wheel axles in mm, for a bonus point. 40t is way out of spec: just saying.

 

[raleighnut]

Why ?