Biggest gearing on short cage ultegra derailleur

[G321]

Got some lumpy rides coming up and think it might be a good idea to make my gears a bit more user friendly. Currently using 11 speed di2 with a pro compact chain set with a max 28 on the back.
Looking at a larger cassette, bit of light reading suggests I can only got to a 30 on the back without changing the derailleur, some suggestions that a 32 would still work. Has anyone tried adding a 32 tooth cassette on a short cage derailleur?

[bobbo89]

I used to push Shimano short cage MTB derailleur's to 32t when I ran 10spd, shortest was a Saint which was DH specific and so really short and it worked fine...

[OutInTheShed]

What some people call a short cage derailleur, others will call a medium cage derailleur.

What you can get away with depends on the range of chainwheels at the front, among other things.

Cage length directly affects the amount of chain it can take up (" capacity"), but other things like geometry of the mech and mech hanger can affect how big a rear cog you can use.

I have a 2 x 10 speed drop bar bike with a cassette going up to 36T. With an old Dura-Ace rear derailleur.
But to do that, I had to lose a couple of teeth from the big chainwheel.

Check Shimano data for derailleur capacity against your actual part number as a starting point.

Whatever you do, be really sure the chain is long enough for biggest/bigger with a link or two to spare.

[G321]

Thanks for the responses. I think I'm going to try it, if it will take a 30 it shouldn't be too much trouble to take the extra 2 teeth. I've used shimano components before that shouldn't have been compatible but it always works!
I will get a brand new chain so I can make sure it has the correct length

[Stick Legs]

It depends what generation of Ultegra. Stuff from the mid 2010's on should cope with quite big gearing as the cage length on a modern rear derailleur is essentially what 'long cage' was in the 1990's.

I ran an 11-32 cassette quite happily on an RD-9000 (which is the Dura Ace equivalent of Ultegra 6800) with a 34-50 chainset.

Just don't cross chain & you'll be fine.

[Johno]

I ran a 34 on that set up, but I use the Di2 shifting to only allow the rear derailleur to run the last two cogs with a front shift to the inner chain ring.

That way I don’t need an extender etc.

Works a treat and I do t need to run a chain long enough for a 50/34 as I never use it.

[numtumfutunch]

Johno said:

I ran a 34 on that set up, but I use the Di2 shifting to only allow the rear derailleur to run the last two cogs with a front shift to the inner chain ring.

That way I don’t need an extender etc.

Works a treat and I do t need to run a chain long enough for a 50/34 as I never use it.

This

Program your Di2 for sequential shifting vis the app

[Harpoon]

Johno said:

I ran a 34 on that set up, but I use the Di2 shifting to only allow the rear derailleur to run the last two cogs with a front shift to the inner chain ring.

That way I don’t need an extender etc.

Works a treat and I do t need to run a chain long enough for a 50/34 as I never use it.

Do you mean you have Di2 setup to block big / big and big / big -1? I know my 8000 series Di2 automatically blocks little / little and little / little +1 to avoid catching the shift ramps on the chainset but I didn't know you could set it to block big / big (unless I'm misunderstanding).

[Johno]

Harpoon said:

Do you mean you have Di2 setup to block big / big and big / big -1? I know my 8000 series Di2 automatically blocks little / little and little / little +1 to avoid catching the shift ramps on the chainset but I didn't know you could set it to block big / big (unless I'm misunderstanding).

A good way to describe it. Di2 blocks lowest 2 cogs if you’re in the small ring. What I have done is use synchro shift in the app to block the largest 2 cogs unless I’m in the small front chainring. If you have a Garmin as well set up to talk to it you get a visible and audible indication your next shift is a front chainring shift.

That way you keep better chain tension, provides some discipline to stop bib/big and allows 34t rear cassette without changing cages/hangers etc.

I also find you fine tune the set up and I very rarely use the left shifter to chain front derailleur. As I use synchro shift on the right shifter.

You can also change the set up with different settings between shift setting on the junction box when you’re riding if you need to. I haven’t needed to, but you’re not app dependent to do it.

[Harpoon]

Ah, you're using full synchro then. I'm using semi-synchro and have never got round to trying full out. One day I'll also add a BT module to the bike for the Garmin integration. I do need to re-tape the handlebars, so that could be a good time to wire it in.