mattscq

Hi all,

So my bike shipped with a Shimano 11-30 11sp cassette and a short cage RD (Ultegra Di2 R8050). I've decided to get another set of wheels for light gravel riding and was thinking of fitting an 11-32 onto it and placing my 11-30 onto my road wheels. I know the short cage RD is rated for a max of 30T but have read/heard/watched videos on how it can actually accommodate 32.

I'm wondering:

1) Are their drawbacks beyond this being a hack? I.e. do you forsee any problems running a 32T on a short cage RD?
2) If I do go with this hack, will it likely require constant RD alignment/limit adjustments whenever I switch wheels/cassettes?
3) Is this a horrible idea? I would be more open to doing it right and just getting a medium or long cage RD but Di2 derailleurs are a fortune.
3b) For the future, if I do decide to get a new RD, is there any reason why I shouldn't just get the longest cage RD with a clutch? Why do people run short cage RDs without clutches if you could get an 11-28 on a long cage as well as 11-34, and you can simply turn the clutch off?

Thanks

shelbyfv

2) If it fits, it fits. No reason for it to require more than proper initial setup.

Andrew R Stewart 

Cage length is not because of large cassette cogs, it's about the cog size difference and the amount of chain wrap needed. Some might say this distinction is too subtle to mater as most all ders that handle large cogs also have a long cage. But I suggest understanding the true design aspects is better then not. Andy (who tries to apply this to other topics like politics or human interactions)

dsbrantjr

You may need to readjust the rear derailleur slightly when swapping wheels due to normal tolerances, these would be the high and low limits and indexing. In addition, if the cassettes have different tooth counts you may need to adjust the guide pulley clearance: https://di2center.com/2019/04/25/how...ar-derailleur/

70sSanO

I don’t to have any design knowledge when it comes to derailleurs.

My understanding is that cage length, as Andy already said, has to do with chain wrap. The design aspect of a low max cog racing rear derailleur is all about speed and performance. When people were running 19t or 21t max cogs and it was about quick and smooth shifts. So you can’t really toss a long cage on a short cage derailleur and run a max cog way beyond capacity.

Derailleurs with higher rated max cogs are designed with enough room to accommodate them. They also are long cage because no one runs a 20-34 cassette. I’ve never cared to delve into the ins and outs of derailleur design, but a larger max cog derailleur is probably designed to sit further down from the hanger to accommodate the larger cogs.

In the end it is all about optimizing performance vs. versatility. It comes down to how you ride. Today’s derailleurs are better designed so there is probably less drop off in performance. If you are looking at a mere 2t change, I’m willing to bet that won’t necessarily suffice. You may want to find a derailleur that gives you a more substantial.

For now, most likely you can push your 30t to 32t. I’ve pushed max and capacity on a lot of setups.

John

Bill Kapaun

Shimano is "conservative" in max cog size, but there are caveats.
All bikes aren't exactly the same when it comes to drop out/hanger geometry.!
What fits on 1 bike may not on another.
Shimano spec's them to fit "worst case" scenarios from the bike manfs. and still function "properly".