105 Di2 and Dura-Ace Parts Swap

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Agent041
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Joined: Fri Sep 08, 2023 11:16 am

by Agent041

pdlpsher1 wrote:
Fri Jun 21, 2024 5:13 am
I found a new Ultegra cage and today I swapped out the cage on my 9250 RD. I also got a 11-36 cassette and took the cluster on the 11-36 and merged it with my 11-34. Shifting is perfect on the bike stand. Tomorrow will be a real test on the road. The Ultegra cage added just 25g. The cassette mod. added 103g (252g to 355g). The stock 11-36 cassette is 377g. I like a wide-range cassette not just for climbing but because I could use the big ring for everything except a steep and long climb. It's like having two 1x drivetrains.
So this probably mean that 11-36 cassette works also perfectly with Ultegra 12speed rear derailleur (original from the box)?

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pdlpsher1
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by pdlpsher1

Maybe or maybe not. The 9250 RD locks out the two smallest cogs. So effectively my 11-36 cassette becomes a 13-36 cassette, reducing the chain wrap by two.


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Agent041
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Joined: Fri Sep 08, 2023 11:16 am

by Agent041

Yes, could then still be an issue. Ultegra 12s does not lock 2 smallest rings when in the small chainring.

Does perhaps anybody else have this info? Or first hand experiance?

I have spare Ultegra rear derailleur. And want to convert my gravel bike to Di2, so would be good to know that I do not need to buy full set of Di2 105 group

OtterSpace
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by OtterSpace

Agent041 wrote:
Fri Jun 21, 2024 7:25 am
Yes, could then still be an issue. Ultegra 12s does not lock 2 smallest rings when in the small chainring.

Does perhaps anybody else have this info? Or first hand experiance?

I have spare Ultegra rear derailleur. And want to convert my gravel bike to Di2, so would be good to know that I do not need to buy full set of Di2 105 group
This is one of the really annoying things with Shimano Di2.

All of this comes from Shimano's teeth drop spec implementation and Shimano not allowing you to set any out of spec settings for non supported chainrings, cassettes, or even out of series parts (like not being able to set 54/40 on anything but Dura-Ace FD). This follow the rules implementation actually makes them blind to what you are actually running which might be within the total system drop spec or out while being out of spec for the FD or RD.

Shimano would rather be blind to what you are running then allow you to set anything out of their very narrow spec window.

If using an Ultegra RD when running a 11-36 physically you can only select 11-30 or 11-34 in the settings. Di2 therefore wont know that you are using a 11-36 and wont lock out the small-small for the smallest two cassette cogs. The total teeth drop of this is out of Shimano's total teeth spec drop for 50/34 and 52/36 so if they knew you were running 11-36 on Ultegra they would lock out the two smallest cogs.

If using a Dura-Ace RD when running a 11-36 physically you can only select 11-30 or 11-34 in the settings. Di2 therefore wont know that you are using a 11-36 and but will lock out the small-small for the smallest two cassette cogs unless you have a Dura-Ace FD with 54/40 selected from what I've read. The Dura-Ace cage is short which is why pdlpsher1 lengthened theirs.

pdlpsher1's setup in a round about way reaches compliance with Shimano's teeth drop specs but the system doesnt know what cassette it is actually using.

Generally Shimano's spec can be pushed a bit before it runs into safety issues and is fairly conservative to preserve shifting quality. However each person has different risk tolerance.

The 105 cage likely will not fit on Dura-Ace or Ultegra from what others have posted.

Agent041
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Joined: Fri Sep 08, 2023 11:16 am

by Agent041

Do you think that setting cassette on 11-34 in the system, when actually 11-36 would be installed, would make it a problem when shifting? Manually the chain would be set so long that all sprockets are to be run. At mechanical Simano, going a bit out of limit was never a problem with shifting,.

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pdlpsher1
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by pdlpsher1

With 11-speed parts one could go out of spec without issues. On the 12-speed parts things might get wonky. It might be safer to just sell the Ultegra RD and buy the 105 or the new GRX RD with a clutch.

Speaking of being out of spec, I’m running 48/31 chainrings with a 9250 FD AND a 11-36 cassette. All is well except the big big gear combo where the chain slightly rub the top of the FD cage. I could move the FD up but that might compromise front shifting. I don’t use big big so it’s not that big of a deal. I’m not running a GRX crank with the wider chain line. I’m using a P2M PM with a road specific spindle to match the 9250 chain line.

There’s a member here who tried a 10-45 cassette with a 105 RD on a 2x crank, and said it runs beautifully!

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Last edited by pdlpsher1 on Fri Jun 21, 2024 8:50 pm, edited 2 times in total.

Ritxis
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by Ritxis

Agent041 wrote:
Fri Jun 21, 2024 6:14 pm
Do you think that setting cassette on 11-34 in the system, when actually 11-36 would be installed, would make it a problem when shifting? Manually the chain would be set so long that all sprockets are to be run. At mechanical Simano, going a bit out of limit was never a problem with shifting,.
in Di2 it is the same, nothing abnormal has to happen.....I have seen in a 11 Dura-ace Di2 a 53-39/11-40 transmission...(Xt cassette)

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pdlpsher1
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by pdlpsher1

On my gravel bike I have 11-speed 2x GRX with a 11-40 cassette. Runs great. But not every frame could do the same.


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