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  1. #1
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    2x9 keeping the big ring

    I did some searching and didn't find an answer so if there is already a thread on this I apologize. I would like to go to a 2x9 setup so I can get a bash guard and a chain guide but I still use my big ring. The thing is I never use the middle ring only the granny gear and big ring. Is it possible to run granny gear and a big ring? Or do I just have to save up for a bigger middle gear? I live in Colorado so I go up alot of bigger climbs but I also do fast stuff like fire roads so I do wanna be spinning all the time.

  2. #2
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    Quote Originally Posted by lagocza View Post
    I did some searching and didn't find an answer so if there is already a thread on this I apologize. I would like to go to a 2x9 setup so I can get a bash guard and a chain guide but I still use my big ring. The thing is I never use the middle ring only the granny gear and big ring. Is it possible to run granny gear and a big ring? Or do I just have to save up for a bigger middle gear? I live in Colorado so I go up alot of bigger climbs but I also do fast stuff like fire roads so I do wanna be spinning all the time.
    What size rings are you currently running? I am assuming 22-32-44?
    Also, what cassette range?

    To answer your question directly, it is going to be pretty hard (if not impossible) to run just a 22t and 44t ring.

    You can't mount the small ring in the middle position (obviously), and putting the big ring in the middle positions can be problematic for several possible reasons. Some cranks can't fit the big ring in the middle position without some filing, and some chainstays will not clear a ring that big so far inboard.

    Even if you overcome those obstacles, you now have a huge jump in ring sizes and shifting is going to be problematic. That is a 22t jump.
    15mm is a second-best solution to a problem that was already solved.

  3. #3
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    yup anything over 15t jump is difficult at best.

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    So I could run big ring and middle ring or small ring middle ring though? I have 22-32-44 and then 11-34 cassette.

  5. #5
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    Quote Originally Posted by lagocza View Post
    So I could run big ring and middle ring or small ring middle ring though? I have 22-32-44 and then 11-34 cassette.
    If you are referring to the ring positions on the crank, small/middle works really well, but middle/big is not that great of a chain line. Also, it is pretty hard to get anything smaller than a 32t on the middle position on most cranks. There are specialty rings out there that let you get a tad smaller (like 30t I think), but that's only about a half gear lower.

    If you use the small/middle position with a 36t in the middle, you are only losing your 2 highest gear ratios compared to having the 44t big ring. Another option is to go with something like a 24t granny and 38t middle, that will gain you about half a gear on the upper end, but you will lose close to a full gear on the low end.

    In general I would not go with a ring difference of more than 14t.

    Also, make sure your chainstay will clear a 36t or 38t ring in the middle position. One of my previous bikes would not clear a 36t (though this is rare). One of my current bikes would be cutting it close with a 38t ring.
    15mm is a second-best solution to a problem that was already solved.

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    Thank you that was extremely helpful, So as long as I keep it within 14 teeth my derailleur should work as long as I adjust it? I think I'm going to go with a 36-22 or a 38-24.

  7. #7
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    Re: 2x9 keeping the big ring

    Going down from 44 to 38 will be much bigger difference than going up from 22 to 27/28. I bet you can manage front 27 with 36 back on any steep climb.
    So I would check out the 42/28 or 42/27 combo if I were you...

  8. #8
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    Quote Originally Posted by Leech73 View Post
    Going down from 44 to 38 will be much bigger difference than going up from 22 to 27/28.
    How do you figure that?

    -Going from 22t up to 27t is a 23% increase in gearing. Up to 28t is a 27% increase.
    -Going from 44t down to 38t is a 14% decrease (or looked at another way, 38t to 44t is a 16% increase). Either way, much less significant.

    Looked at another way: with an 11-34 cassette, with a 27t granny his lowest ratio will be about the same as his current 22t granny in 3rd cog. In other words, by going to a 27t ring, he is loosing his two lowest gears. Going from a 44t to a 38t big ring, his highest gear will be a tad higher than his current second highest gear. In other words, he will be losing LESS then one gear on the top end.

    I bet you can manage front 27 with 36 back on any steep climb. So I would check out the 42/28 or 42/27 combo if I were you...
    First, he is running 9 speed, so an 11-36 cassette is not an option (going with a 12-36 would be counterproductive as it has less range, and knocks down his highest gearing). Second, he is converting a 9 speed crank, so those ring sizes might not even be an option.


    I guess in the end of his gearing he is more willing to lose. I think your idea makes sense if you want to take it all off the bottom.
    Last edited by kapusta; 04-26-2013 at 01:42 PM.
    15mm is a second-best solution to a problem that was already solved.

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    Quote Originally Posted by kapusta View Post
    How do you figure that?
    Calc with speed, not %. Difference between 44/11 and 38/11 is about 3,5 mph, diff between 27/34 and 22/34 is about 1mph..

    Quote Originally Posted by kapusta View Post
    First, he is running 9 speed, so an 11-36 cassette is not an option
    My bad...sorry

    Quote Originally Posted by kapusta View Post
    Second, Remember he is converting a 9 speed crank, so those ring sizes might not even be an option.
    He can always put 10sp rings on it, will work fine in most cases

  10. #10
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    Quote Originally Posted by Leech73 View Post
    Calc with speed, not %. Difference between 44/11 and 38/11 is about 3,5 mph, diff between 27/34 and 22/34 is about 1mph..
    % is much more relevant.

    Why do you think that the cassette tooth counts are so much closer between the small cogs than the big ones? It is in order to keep the % ratio jumps roughly consistent. Notice that the increase in spread gradually increases? This is especially noticeable on an 11-36 cassette.

    This is also why on triples that have a 22t granny and 44t big ring that the middle one is at 32 (closer in count to the small) rather than 34 or 36.

    Think about the example you just gave as the difference in crank rpm to maintain a given speed typical of going DH (for the 44/11 and 38/11) and a slow steep grind (22/34 and 27/24). You will see that it is more affected in the 22-27 jump than the 44-38 drop.
    15mm is a second-best solution to a problem that was already solved.

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    I agree with the reason for the tooth count steps on the larger cogs, to gradually de- or increase speed while maintaining roughly the same rpm.
    But this contradicts with your remark on keeping rpm for a given speed when comparing the different ratios.
    Again, %-whise you are right, but what difference does it make to go up a steep hill with either 6 or 7 mph?
    Going down a fast straight with or 25 or 28,5 mph makes a more sensible difference to me..

    Maybe we should agree to disagree on this one..

  12. #12
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    Quote Originally Posted by Leech73 View Post
    I agree with the reason for the tooth count steps on the larger cogs, to gradually de- or increase speed while maintaining roughly the same rpm.
    But this contradicts with your remark on keeping rpm for a given speed when comparing the different ratios.
    Again, %-whise you are right, but what difference does it make to go up a steep hill with either 6 or 7 mph?
    Going down a fast straight with or 25 or 28,5 mph makes a more sensible difference to me..

    Maybe we should agree to disagree on this one..
    Instead of looking at it from a % perspective, because you may not be able to know what that actually feels like on the trail, I look at it like something I can relate to on the trail; you basically lose one gear off the top end when figured in gear inches. . . . actually, it's a little less than that. I have included a screenshot of a spreadsheet I made to figure this stuff out. The green and blue columns show what that would translate to in m.p.h. for both 60 and 100 cadence. The red and purple highlighted cells show the top end specs we are discussing.

    FYI: The 88.6" circumference is the rollout of the 29er wheels/tires I was using at the time I made the spreadsheet.
    Attached Images Attached Images  

  13. #13
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    Huh, I responded to this yesterday, but the post is gone
    Quote Originally Posted by Leech73 View Post
    I agree with the reason for the tooth count steps on the larger cogs, to gradually de- or increase speed while maintaining roughly the same rpm.
    But this contradicts with your remark on keeping rpm for a given speed when comparing the different ratios.
    No, that was not what I was saying. The tooth counts do NOT give you a consistent (if that is what you mean by "gradual") increase in speed for a given crank RPM as you move through the cassette cluster. The increase between gears is greater between the higher gears than between the lower gear.

    What I said was that the % difference between the gears remains roughly consistent.

    What you are focusing on (speed for a given rpm) is proportionally related to gear inches. Look at the table of gear inch calculations below. Notice how as you go from the lowest to highest gear, the increase in gear inches gets greater between gears?

    Why this is the case? It is because adding or subtracting a given number of gear inches (which can be converted to speed for a given crank rpm) makes a bigger difference in a low gear than a high gear.

    Let me ask you this: If what matters is comparing MPH for a given crank speed, or gear inches (rather than % differences), then why are cassettes laid out to give consistent % differences rather than consistent absolute differences in gear inches? According to your logic, mtb cassettes all have too-closely spaced ratios at the bottom end.

    Again, %-whise you are right, but what difference does it make to go up a steep hill with either 6 or 7 mph?
    Going down a fast straight with or 25 or 28,5 mph makes a more sensible difference to me..
    First, going up a steep hill requiring a 22/34 combo we are talking more like 4 mph.

    The amount of exertion required to add 1mph to a steep climb (which is what you would be doing keeping a consistent crank rpm going from 22/34 to 27/34) is very significant (23% more). More likely you will end up going the same speed, lower your cadence 23% but require 23% more force on the pedals.

    However, dropping from a 44/11 to a 38/11 will only require a 14% increase in crank rpm to make up for the lost speed you are quoting. You see, the higher gear ratio means that slight changes in crank speed result in bigger changes in ground speed than with lower gear ratios.

    Again, this is the reason that gear inch jumps get bigger between higher gears.

    To the OP trying to make sense of this:
    Try this: Next time you are grinding up a hill in 22/34, try switching up two gears (this will be like running 27/34). Then next time you are bombing DH in 44/11, try shifting down one gear (which will like running 38/11). See which you notice more.
    15mm is a second-best solution to a problem that was already solved.

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    Re: 2x9 keeping the big ring

    I am not going to respond to your questions (though maybe retorical), to save us from an endless discussion. But I'm glad you summarized it to the OP, because essential in this is that he makes up his mind based on our suggestions and in the end the best way to determine what works is by riding..

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    It is important, however, to recognise that Kapusta has it right on this one. It is the ratio (or percentage if you like) that is important, not the absolute amount of teeth.
    If you look at a 44/11 combo, every time you turn the pedals 1 revolution, the wheel goes around 4 times (as 44 links are moved for every revolution, and 11 of them = 1 wheel revolution). If you go to the 12, you get 3 2/3 revolutions.....a difference of 9.1% in distance covered, or speed.

    At the other end...
    44/32 combo is 1.375 revolutions
    44/33 combo is 1.333, a 3.1% change in speed or distance covered.

    The point is that you need a larger amount of teeth to make the same perceived change in effort the lower the gear.
    The effect is reversed on the front....a change in the small ring by a couple of teeth has a larger % change in the gearing than the same amount of teeth on the large cog.
    Rimmer - "There's an old human saying - if you talk garbage, expect pain"

  16. #16
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    Ok, once more...
    I love this number crunching too (and I DO get it...), but let's not go overboard.
    I'm not saying anyone is wrong, I just look at it from another perspective. I don't care if I climb a hill with either 6 or 7 mph, but 25 or 28 down a straight....

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