Shimano rear derailleur 'top sprocket_max' - Can it be exceeded? Affected by b-screw?
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  1. #1
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    Shimano rear derailleur 'top sprocket_max' - Can it be exceeded? Affected by b-screw?

    I'm considering using a rapid rise rear derailleur so the bar end shifters on my gravel bike make sense but it seems a lot (if not all, I can't find specs for the old parts I'm looking at...) MTB rear derailleurs are listed with a 'top sprocket_max' vaue of 11t.

    Does anyone have experience of exceeding this? I guess if the sprocket is too big (I'm thinking 13-34 cassette) the top jockey wheel will hit it and it will sound bad, but maybe the b-screw can help?

  2. #2
    'brifter' is a lame word.
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    Where are you planning on finding a 13-34 cassette?
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

  3. #3
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    13-34 will take at least two donor cassettes with 13-14-15-16 from an HG50-9 13-25 and 17-20-23-26-34 from an HG41-8 11-34 being the cheap and easy option, remove the rivets and sand the spacers if the 0.1mm extra thickness from the 8 speed sprockets ruins the indexing or just friction mode on the shifter.

    That's irrelevant if I can't convince a rapid rise to work with the 13 top though as close ratios starting at 11 combined with a Low sprocket_Min. of 32 is pushing it, plus that means different chainrings.

    Feel free to tell me if I'm being stupid, most of my 'wrenching' this far has been in my head!
    Last edited by suicidal_orange; 05-11-2019 at 01:40 PM.

  4. #4
    'brifter' is a lame word.
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    I'm not even going to try to figure out why you're thinking about going through all the trouble.
    I work for some bike racers
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    and a bunch of skateboards

  5. #5
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    Pro Link Gold for $1000, Alex

  6. #6
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    Quote Originally Posted by cxwrench View Post
    I'm not even going to try to figure out why you're thinking about going through all the trouble.
    All the trouble? Six rivets and a couple of minutes with some sandpaper probably takes about as much extra time as wrapping both sides' bar tape perfectly matching (for someone with my level of experience) and I bet most newbies try to do that. It's not like I'll be changing the cassette often as I only ride about 160 miles a week.

    I have tried to research before asking but unsurprisingly it's not something that gets discussed...

    If you want to know I'm considering this read on, if not feel free to answer the original technical question as a standalone - you seem very knowledgabe


    As I said most of my riding is relatively flat and I use bar end shifters because I like being able to shift multiple steps at once (often have to slow significantly for dog walkers and short, steep 'hills' for canal bridges). With a standard rear derailleur in high gears the shifter is pointing towards the floor to varying degrees, slightly forward of vertical for top gear. It is more comfortable to reach to change gear when the lever is near horizontal and while searching I found out about rapid rise which reverses the order. Sounds like it would be perfect, but only if it works.

    Quote Originally Posted by rideit View Post
    Pro Link Gold for $1000, Alex
    You'd like some overpriced chain lube

  7. #7
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    If anyone cares I gave this a go and put an SGS axle mount Hone derailleur on my gravel bike along with the 13-25 cassette I was already running - too big at the top and too small at the bottom.

    The derailleur says it's for vertical dropouts but the instructions clearly show slanted ones, the result is b- and 'bump stop' screws that do nothing and a derailleur that assumedly sits at the wrong angle. Fortunately because of the angle the jockey wheel is nowhere near the cassette anyway and it shifts quite happily using a 10 speed MTB bar end shifter and a Shiftmate 8 (which is supposed to be for mixing 11 speed MTB/road)

    If I swap in a 14t jockey it would be closer to the cassette which the instructions say is good, I'd ask if that's something I should do but doubt there's any point. Will update if I do it.

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