# Dura Ace 10 spd and 11 spd rear cog capacity?



## David23 (Jun 5, 2012)

I've tried to find this info, but seem to be missing it. I have two bikes, one a couple years old Dura Ace 10 spd, currently running 11-28 without issues. The other new bike with DA 9000 11 spd, and 12-28. I'd like to increase the size of the rear cog to assist my climbing in steep areas I frequent. At 65, I need a bit more help up some of the PV hills. How do I know if an 11-32 (or 12-32) will work with my derailleur? I know the Shimano specs give a range, but my understanding is that is conservative, and in actual practice a larger cog can work without problems. I don't see an indication on the arms whether they are long, short, medium or what.


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## ericm979 (Jun 26, 2005)

If your derailleur is spec'd for a 27t or 28t cog it can very likely handle a 30t. It depends on the length of the frame's derailleur hanger. But the only person I have heard of who has not had it work had a shop do it and they sized the chain incorrectly (too short) which broke the derailleur when he shifted into the big ring/large cog combo. 

A very few I know have had a derailleur spec'd for 28 work with a 32t. Mostly with Di2 derailleurs and using smaller jockey wheels for clearance.

If your derailleur is specd for a 30t cog it can probably handle a 32t. Some newer Shimano derailleurs are specd for 30t.

The cage length does not dermine the maz cog size. It determines the chain wrap. Which also can be somewhat over the spec, especially for Shimano.

I've run 30t cogs on Shimano 7800 and 7900 and Sram Red 10sp.

Find the model number on your derailleur and look the specs up on line. It is often on the back (wheel) side of the paralellogram (the arms that pivot on the frame size and move the jockey wheels in and out).


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## MMsRepBike (Apr 1, 2014)

Dura-Ace has never been spec'ed for anything bigger than a 28 tooth cog.

So technically you have to get an Ultegra rear derailleur to do it correctly.

However.
Your derailleur actually does have the ability to run an 11-32 PROVIDED you have a frame/derailleur hanger that is considered long or steep.

On the majority of frames it's not going to work well. You will not be able to screw the b-tension screw in enough to have the top jockey wheel stop hitting the big cog. There just won't be enough clearance. If you're lucky though your derailleur hanger will be built in such a way to give you more b-tension movement/adjustment towards larger cogs.

The Ultegra 11 speed GS derailleur is specifically designed for large cassettes and will work flawlessly. Anything else will be an experiment of sorts.


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## David23 (Jun 5, 2012)

MMsRepBike said:


> Dura-Ace has never been spec'ed for anything bigger than a 28 tooth cog.
> 
> So technically you have to get an Ultegra rear derailleur to do it correctly.
> 
> ...


How do I know if my hanger is long or steep? I have S works Roubaix and S works Venge. Any idea?


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## cxwrench (Nov 9, 2004)

David23 said:


> How do I know if my hanger is long or steep? I have S works Roubaix and S works Venge. Any idea?


The last sentence of @MMsRepBike's post says it all: "Anything else will be an experiment of sorts." 

The only way to know is to try. Or hope someone w/ your same frame has done it and can post their results.


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## CliffordK (Jun 6, 2014)

The other thing to consider, of course, is decreasing the size of the front chainring. 

I think 110 bcd cranks can go down to 34 Teeth, even the new FC9000.


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## David23 (Jun 5, 2012)

CliffordK said:


> The other thing to consider, of course, is decreasing the size of the front chainring.
> 
> I think 110 bcd cranks can go down to 34 Teeth, even the new FC9000.


I'm already running a compact 50-34 in front.


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## woz (Dec 26, 2005)

I've done a 32 on a bunch of different DA mech and Di2 bikes, longer hangers do help but are not necessary. Remove the b-screw and put it back in from the opposite side of the plate as well as replace your upper pulley with a 10t and you should have plenty of clearance. You'll of course want to avoid cross chaining (50x32 or 34x11) but other than that you should be fine.


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## cxwrench (Nov 9, 2004)

woz said:


> I've done a 32 on a bunch of different DA mech and Di2 bikes, longer hangers do help but are not necessary. Remove the b-screw and put it back in from the opposite side of the plate as well as replace your upper pulley with a 10t and you should have plenty of clearance. You'll of course want to avoid cross chaining (50x32 or 34x11) but other than that you should be fine.


So it 'kinda' works, as long as you avoid some gears. Sorta. W/ a b-tension screw reversed. That's pro.


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## goodboyr (Apr 19, 2006)

Just did an install of DA9070 with a 6870 GS RD with 11-32 / 50/34...........perfect shifting. All this playing around is not worth it. Bite the bullet.


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## David23 (Jun 5, 2012)

My shop ordered an Ultegra RD 6700 GS, (10spd) which is the longer arm. We are hoping this will work with an 11-32 cassette. The Shimano specs say it has a 30t max cog size, but a 40t capacity. I don't understand the difference. Will I be reliably ok with this arm and the 11-32 cassette?


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## Bevo (Dec 26, 2012)

Works fine with my 9000, I used the 11-32 in Italy, we adjusted the B screw, pretty simple and worked perfect.
Just make sure the chain is long enough.

Short cage Ultegra 10-11 speed also works with adjustments.


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## CliffordK (Jun 6, 2014)

David23 said:


> The Shimano specs say it has a 30t max cog size, but a 40t capacity. I don't understand the difference. Will I be reliably ok with this arm and the 11-32 cassette?


32T Cog Size is the biggest cassette it is rated for. Some people have stated this may be a conservative estimate, so you'll just have to try it out.

40T "capacity" is total amount. (Largest Chainring + Largest Cassette Cog) - (Smallest Chainring + Smallest Cassette Cog)

So, you said you had 50/34 in the front, and 11/32 in the back.
So, 50+32 = 82, 34+11 = 45, 82-45 = 37T, so you are just a little bit under the maximum chain wrap (which may also be conservative). If you never do 100% cross-chaining, you may even be able to fudge that number a bit, although that would be a good way to break something.


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## ziscwg (Apr 19, 2010)

goodboyr said:


> Just did an install of DA9070 with a 6870 GS RD with 11-32 / 50/34...........perfect shifting. All this playing around is not worth it. Bite the bullet.


WHAT????

Buy the right tool/part for the job?????

OMG, Where's the fun in that? 

Hours, and hours and hours of "MacGyvering" it has a lot of satisfaction. After you get it going, you still get to mess with it all the time. 

Or, you could buy the right RD, set 3 screws, put on your new chain and go out riding.


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## goodboyr (Apr 19, 2006)

Well said.....


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## David23 (Jun 5, 2012)

ziscwg said:


> WHAT????
> 
> Buy the right tool/part for the job?????
> 
> ...


Yeah, buy the right part and have it work….. what a concept. I'm hopeful this is the right part and will work as it should (sounds like it will from the answers I have received). I ride solo a lot, and don't want to have to "MacGyver" by the side of the road. I'll post the results.


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## deviousalex (Aug 18, 2010)

Art's Cyclery Blog » Ask a Mechanic | Wide Range Cassettes With Shimano Road Derailleurs

Some good info here.


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