Huge chainring and cog without any tensioner - is it possible?- Mtbr.com
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  1. #1
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    Huge chainring and cog without any tensioner - is it possible?

    I have never ridden a single speed before. I would like to ask three questions to single speed riders, who have tried different size configurations:

    Is it more difficult to drop chain with bigger chainring and cog, for example 56-28 vs. 32-16, everything else the same?

    Is it theoretically possible to have such a huge chainring and cog combination, that a chain doesn’t drop without any tensioner or horizontal dropout - only tensioning chain during assembly with powerlink?

    What’s the biggest cog single speed riders use?

  2. #2
    SS Pusher Man
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    The limiting factor to using a really large front ring is usually the frame. On some frames the ring will hit the chainstay.

    The size of the ring/cog doesn't matter all that much when it comes to chain tenstion/retention. Even with a magic gear, once the chain stretches out and you get enough slack, the chain can/will jump off.
    Bicycles don’t have motors or batteries.:nono:

    Ebikes are not bicycles :nono:

  3. #3
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    Updated post:


    Thanks!

    Yes, 29” mtb frame could have the problem with chainstay. Some 26” or trekking frames can handle bigger rings.


    For me it is more important an answer to the question: how much ring/cog size matter? I can only think about it theoretically, because I have no experience in the single speed area.

    Yes, chains stretch with time, but the process could be much slower when using bigger cogs.

    To move wheel we need enough torque (torque being defined as force at a specific radius). If we use bigger rings and bigger cogs automatically radius is also longer, so force could be lower to maintain the same torque. With a larger front ring and rear cog chain tension should decrease due to a longer effective moment arm. So, it could slower the stretch process of the chain.

    Now I understand you point of view. Magic gears even when exist, could become less magic with stretched chain
    Last edited by SmoothestRollingBike; 01-25-2016 at 10:12 AM. Reason: I have written SS FAQ

  4. #4
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    Anybody has experience with vertical dropouts, no tensioner and very big cogs and rings?

    Update: now I know it is possible, but not practical with 29" mtb.
    Last edited by SmoothestRollingBike; 01-25-2016 at 10:10 AM. Reason: I have written SS FAQ

  5. #5
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    You really need to read the SS FAQ sticky, all these questions have been asked and answered hundreds of times at least

  6. #6
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    Yes, you are right. I have found information, what does “magic gear” really mean. Thanks. I will correct my previous posts.

    Unfortunately the website with ssConvert Single Speed Software doesn’t exist

  7. #7
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    magic gear = chain ring / sprocket combo where the chain is perfectly tensioned while having vertical dropouts, fixed BB and no tensioner. As above, chain stretches, magic goes away, chain comes off.

    fyi I run a 52 - 18 on my commuter with no issue but it does have horizontal drops (not SS frame though), no tensioner .

  8. #8
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    Do you measure how much your chain is stretched with miles or km? It should be more time to stretch chain in comparison with 2x11, or am I wrong?

  9. #9
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    I was thinking theoretically about:

    Pinion’s rear spider (104 BCD) with 32t cog

    ring: something between 56t-70t

    It could be extremely low friction in the drivetrain, but probably nobody here using such huge cog.

  10. #10
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    OK, now I see how ridiculous my thought were.
    Off-road – too small ground clearance (ring)
    On-road – even 70t ring could be too small

  11. #11
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    Huge chainring and cog without any tensioner - is it possible?-100bike2-001.jpg

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  12. #12
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    104 teeth Royce chainring and this ratio…

    …maybe, when I will train a little more…

  13. #13
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    Quote Originally Posted by SmoothestRollingBike View Post
    Yes, you are right. I have found information, what does “magic gear” really mean. Thanks. I will correct my previous posts.

    Unfortunately the website with ssConvert Single Speed Software doesn’t exist
    Looks like the Fix Me Up magic gear link is broken, here it is below. Even if you don't try magic gear it is still useful for getting a swag at link count for something like an ENO rear hub which is a good alternative to a tensioner and looks as clean as a real SS.

    ENO ? White Industries

    http://eehouse.org/fixin/formfmu.php


    Last edited by socal_jack; 01-26-2016 at 09:11 AM.

  14. #14
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    using bigger cogs and rings is not going to change the importance of chain tension. if the chain is loose enough to fall off the rings, it's going to be loose enough to fall off if the ring is a 55t or a 22t. loose is loose.

    you could probably put something like a 42-48t ring on a mountain bike if you put it in the position that the big ring on a triple would be. you just need to space the rear cog on the hub accordingly to match the chainline.

    22t rear cogs are common, but I can't think of anyone who makes one bigger than 24t.

    you seem to have picked up on the other problem- clearance. I would not want anything bigger than a 44t on a mountain bike for fear of bashing it on rocks, but I have never had anything bigger than a 33t on any mountain bike I have owned (all SS or 1x9).

  15. #15
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    Jack has an Endless brand 24t cog sitting on the dresser next to an Eno eccentric hubset. Now Jack is thinking dingle cross bike. Thanks for the idea. But that's not mountain biking.

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