12-25 on 6870di2 GS? shimano says it can't be done
formadelfo
Posts: 3
Hi Guys,
i have a 6870 (11spd) ultegra di2 equiped bike. Front 50/34 and rear 11-32. This is ideal for climbing, but i live in the netherlands and the profile of a typical round through the netherlands is _________. So i bought a 12-25. After installing i wanted to adjust some synchro shifting settings and i couldn't choose the 12-25. After some research i found on the shimano website that my GS derailleur needs a 28 max sprocket as a minimum. So the 11-28 is the smallest cassette i can fit. This was new for me, because i thought there was only a problem if you go to big (and nog when you go to small). As you can read all over the internet, you can go a bit bigger then what Shimano says. Is it also possible to go smaller then Shimano says? Obviously i would need shorter chain, and from what i have found i should adjust the B screw so the hanger of the derailleur will rise a bit up (closer to the cassette). I also found that you can buy seperate hangers for derailleurs. Might buying a SS hanger solve my problems all together...? But my main question is, will it shift OK, am i missing something and won't i break something? Anyone any experience with these kind of situations?
Greetings,
Joost
i have a 6870 (11spd) ultegra di2 equiped bike. Front 50/34 and rear 11-32. This is ideal for climbing, but i live in the netherlands and the profile of a typical round through the netherlands is _________. So i bought a 12-25. After installing i wanted to adjust some synchro shifting settings and i couldn't choose the 12-25. After some research i found on the shimano website that my GS derailleur needs a 28 max sprocket as a minimum. So the 11-28 is the smallest cassette i can fit. This was new for me, because i thought there was only a problem if you go to big (and nog when you go to small). As you can read all over the internet, you can go a bit bigger then what Shimano says. Is it also possible to go smaller then Shimano says? Obviously i would need shorter chain, and from what i have found i should adjust the B screw so the hanger of the derailleur will rise a bit up (closer to the cassette). I also found that you can buy seperate hangers for derailleurs. Might buying a SS hanger solve my problems all together...? But my main question is, will it shift OK, am i missing something and won't i break something? Anyone any experience with these kind of situations?
Greetings,
Joost
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Comments
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I will be interested to hear replies to this too!Felt F70 05 (Turbo)
Marin Palisades Trail 91 and 06
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Scott Foil 180 -
Hi,
I'm not sure about the 12-25 but I fitted a Medium cage to my Short cage 6870 rear mech with problems at all. You need to buy the inner and outer plates only. Total cost is about £30..
The part numbers are below.
Y5YC98050 Plate Axle Assembly (SS-type)
Y5YC98060 Plate Axle Assembly (GS-type)
Y5YC98070 Outer Plate & Plate Stopper Pin (SS-type)
Y5YC98080 Outer Plate & Plate Stopper Pin (GS-type)0 -
Thanks for the info!0
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I see no reason at all why it won't just fit and ride just fine, the lateral gear spacing is the same.
You'll probably have to do without the auto shifting for the front though as it won't know where its at (but you could just try it).
As 25 is less than 28, then it's fine under the '28 max' requirement.......Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0 -
The problem isn't the mechanical aspect, it's the software programmingFFS! Harden up and grow a pair
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