what size rear derailleur

[John Dombrowski]

So I am getting ready to upgrade to a Shimano XTR Di2 rear derailleur. I ride a Specialized Turbo S and don't know if I need a mid or long derailleur with my stock cassette and chain. I think the biggest ring on the back is a 48T?
Any help on my decision?

Thanks.....JD

 

[John Dombrowski]

So I am getting ready to upgrade to a Shimano XTR Di2 rear derailleur. I ride a Specialized Turbo S and don't know if I need a mid or long derailleur with my stock cassette and chain. I think the biggest ring on the back is a 48T?
Any help on my decision?

Thanks.....JD

Anybody?

 

[Douglas Ruby]

John, I don't know either, but the cage length should be the same as the one you have. Measure it and see if you can compare with specs online. I read somewhere that long is for bikes with multiple (double) front chainrings while medium is for singles, but I can't attest to that.

 

[Ann M.]

Yes, you are mostly correct, Douglas; and since the Specialized Turbo S only has one chainring in the front @John Dombrowski just needs the Medium length derailleur. It's used for single or double front chainrings and the longer version is for a triple setup in the front.

 

[John Dombrowski]

Yeah the Specs on their website says the stock XT derailleur is an SGS which is a long cage but I found out from the bike shop that I can use a GS with the stock cassette so I will go with that in case I want to put on a smaller cog cassette later since I never use all the big cogs anyway.