Blocking off 2 gears on Shimano DI2
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  1. #1
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    Question Blocking off 2 gears on Shimano DI2

    Does anyone know if you are able to block off 2 gears on DI2's without doing damage to the derailed mechanism. I have a junior racer that can only have a his smallest cog as a 16. So I need to block off the 14 and the 15 gears on his 28X14 junior cassette

  2. #2
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    You've got a junior on Di2? Ok...

    The only experience I have w/ this is as follows: If you block off a gear or adjust a limit too tightly and the rider tries to shift past the limit the derailleur will keep trying to shift until something stops it. That would be either shifting back in the opposite direction or the battery going dead. I don't know if the limit screws will even go in that far. Your best option is to get the correct chainring so the the rider can use all cogs. What size chainring do you have now that's so big you have to block off those cogs? 50 x 14 is 96ish inches, 52 x 14 is 100.2.
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    Could you just swap the 14t and 15t with two more 16t cogs?

  4. #4
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    The 16t cogs aren't designed to interface w/ a lockring.
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  5. #5
    JSR
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    It seems 52x14 is the limit for road racing juniors when using 700x23 tires. The 16 cog limit would only come into play in track applications. “Blocked” gearing is specifically not allowed.

    Here is an old USAC guide explaining it all. And here is a good Leonard Zinn article on topic.

  6. #6
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    Wish that was possible. These are the cogs as it stands.
    • 14-28T - 14-15-16-17-18-19-20-21-23-25-28T

    You would have to change from 21, 23, 25 & 28 and they are clumped together in a solid unit.

  7. #7
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    I am based in South Africa. It comes to play in road situations.

    These are the root backs.

    Under 19: 7.93 metres. 52/14Under 17: 6,897 metres. 52/16. Changing to a 50 on the front does not make the difference neededUnder 15: 6,626 metres. 52/17Under 13: 6,227 metres. 52/18Under 11: 6,227 metres.

    Here is a great site for those interested. BikeCalc.com - Fixed Gear Calculator.

  8. #8
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    Can the two smallest cogs be locked out via the Di2 app and if so would this be accepted by the race officials?

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    Would a subcompact crank help?
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  10. #10
    JSR
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    Quote Originally Posted by dannyaaron View Post
    I am based in South Africa. It comes to play in road situations.

    These are the root backs.

    Under 19: 7.93 metres. 52/14Under 17: 6,897 metres. 52/16. Changing to a 50 on the front does not make the difference neededUnder 15: 6,626 metres. 52/17Under 13: 6,227 metres. 52/18Under 11: 6,227 metres.

    Here is a great site for those interested. BikeCalc.com - Fixed Gear Calculator.
    I think you’re looking at the old spec. New guidance was issued by CyclingSA on 8 January, 2018:


    • Youth riders U17 are only restricted to gear restrictions to a distance of equal to and not more than 6,897 metres.

    https://www.cyclingsa.com/road-cycli...20restrictions

    edit: ah, but 6.93 50x15. Yer still screwed.
    Last edited by JSR; 2 Weeks Ago at 01:16 PM.

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