Hi American chums. I have a 2015 Felt B12 with 52/38 chain ring and stock 11/28 cassette. I want to know if anyone has successfully swapped to either 30/32 cassette? I have a hilly race I need a get out gear for!
Does your rear derailleur have a short or medium cage?
Whatever it came with, I’m not sure, looks like this
First thing is to check how many teeth your rear derailleur can handle. So you need to know the model. For instance a particular series of Shimano 105 short might be ok up to 30 teeth and a medium might be ok up to 32 teeth. If it is ok then you probably need a new chain because it needs to be a few links longer for a bigger cassette.
I have a b14 and am looking at going to a 30/32. My LBS said it should be easy but I will need a new derailleur, FYI.
I think the 2015 B12 came with Ultegra 6800 derailleurs. If so the rear derailleur would almost certainly have been a short cage version as used on the vast majority of road bikes/tri-bikes. Best thing i sto look up Shimano’s website for the Ultegra 6800 datasheets. They say the short cage derailleur is compatible with cassettes up to a maximum of 28 teeth. However many people have reported successfully using them with 30 tooth sprockets. It is likely to depend on the total difference in chain length between your smallest and largest gear combinations. So 38+11=49, and 52+30=82. That’s a difference of 82-49=33. So the derailleur has to be able to accommodate 33 chain-links worth of slack. Shimano should also have a figure for this in their derailleur spec sheet. I suspect the short cage derailleur can’t handle that much. So, you can probably get away with a short cage but only if you never use one or both of the extreme combinations of 38/11 or 52/30. You probably wouldn’t use these gears intentionally anyway since that’s big cross chaining but it can and does happen unintentionally and I wouldn’t risk it.
I recently put an 11-32 cassette on my Ultegra 6800 equipped road bike for an alpine event, and I replaced the short cage rear derailleur with a medium length version to do so. All works fine but it did cost me about €55 for the derailleur (on sale).
My b12 came with dura ace 9000, which doesn’t have a long cage option (if I recall correctly). I think 28 is the max recommended. I’m not 100% if I have the 2015 or 2016, but I think the models were identical.
Oh yes, the B14 is the Ultegra version isn’t it?
Still, there should be no problem swapping a Dura Ace rear derailleur for an Ultegra 6800 one. They’re both Shimano 11 speed.