tree2

I have an 11-26 10 speed with Ultegra Di2 and would like to exchange the cassette with a 11-34 10 speed cassette (Shimano CS-HG500-10-speed Road Mountain Cassette 11-34). Is that compatible? Will I run into problems?

Also looking to exchange my 52/36 chainrings for 50/34.

What am I missing? Am I headed for trouble?

Any help appreciated.

NextDIYikeproj

A 34t cassette will probably be to big. I think the small cage reaches up to 28t. You might be able to “hack” it with a wolf tooth goat attachment and fiddling with the b limit screw, but likely not.

if you change the chain rings you might have to shorten you chain. But do it once you have successfully installed your cassette as that is larger than the one you have now.

cxwrench

Pretty bad advice suggesting the Road Link on a bike w/ double chainrings. While they allow the derailleur to clear a larger cog they don't increase the capacity of the derailleur at all. That's why this type of thing is discouraged...it's even mentioned on Wolf Tooth's site.

NextDIYikeproj

Im not suggesting it, I said “you might” and finished off with probably not.

squirtdad

Not sure at all how the Di2 works but you would need a long cage version for this to work....beyond that I have no idea about the electronic side

tree2

Thanks for the replies and helpful suggestions. I've seen videos of guys replacing their 11-26 with an 11-34 with no issues... I'm old enough to know not everything you see on YouTube is real but it got me wondering... I've also been told you can replace the short cage with a long cage without changing the derailleur - just the cage? Is that a thing?

Again thanks!

NextDIYikeproj

Yes, the cage is mounted with two hex bolts. If you find a long cage you can replace it.

Let us know how you do!

woodcraft

Apparently 11/32 will run OK:

Chuckles1

Interesting; I never thought of that when I changed 12/25 to an 11/34. I just bought a longer cage derailleur (GS) and a new chain. What a difference it made for my old legs in hill country.

tFUnK

A RD extender will help you clear the 34t max cog, but you need to pay attention to the chain wrap as well. In your case going from 52/36 to 50/34 keeps the front at 16t, but going from 11/26 to 11/34 increases the rear by 8t to 23t. That's 39t (16+23) of chain wrap and you need to check whether your current RD can handle that (likely not). Finally, your overall chain length may not be long enough to accommodate the net 6t increase (+8r, -2f) so you may need a longer chain.

70sSanO

From what I can tell the Ultegra RD-6770 was only a short cage. The RD-6700-GS has a max cog of 28t. Neither will get to 34t.

This is an interesting video that answers your question about swapping cages. A 6800 GS cage is used, I guess a 6700 GS cage would be equally good. The person in the video is using a derailleur extender, which may suggest that the RD-6700/6770 design will not go to a 34t regardless of the cage length. Cage length has to do with wrap, but I think there are design changes in some RD's to allow a larger max cog with a longer cage so more wrap can be meaningful when used in a non-triple crank world. Warning: It is tough to watch the re-assembly without cleaning first.


John

TGT1

I've been running a 48-34 / 11-34 with a SRAM medium cage for a couple of years now, no problems. Seems like there's enough take-up that a 50-34 would probably be fine, at least with the dr I'm running.

A short cage would probably run out of wrap.

tree2

So I wanted to make sure all was well before letting you know how it went. I've got a couple hundred miles into the new drivetrain now. No super long climbs yet but plenty of shorter and steep climbs. So moved to the 50/34 compact chainring and a 11/32 cassette without changing any detailers. Still using the short cage Di2. Had to screw the B screw ALLLLLLLLL the way in to get it sounding smooth. Took a few rides to get indexing dialed in but all is well. Obviously avoiding the 50-32 combo (big/big) but running great and smooth as silk. Love the 34-32 combo option for the steep stuff. Great to have a bail out option even if not used a lot yet.

Thanks for all the advice!

squirtdad

Does Big/Big work?

If not you are setting your self up for a dangerous situation if you go into that combo unplanned. Get a longer chain

I have had this happen to me...I had a set up i knew did not work Big/Big and didn't have time to get a replacement(longer) chain. I was very aware of this for one whole ride, and got in situation where I automatically shifted, hit Big/Big and everything stopped. Luckily i was going really slow, and had a slow tip over type fall. At speed I have little doubt it would have hurt badly.

tree2

Yes big/big "works". It will shift onto it just fine without consequences but have made sure I don't do that when pedaling hard. And yes, I did replace the chain in the process too. I think if I accidentally shifted into that combo I'd be ok but am very aware and avoiding that just in case...

squirtdad

super...I used to think this was silly until it happened to me.

fwiw theoretically with the narrower 11 speed chains being more flexible....big/big and small/small are supposed to be less of a problem than olden days 5 speeds