26FS Geared to 29SS Rigid: Cog Ratio Differences?- Mtbr.com
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  1. #1
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    26FS Geared to 29SS Rigid: Cog Ratio Differences?

    My 29er SS Rigid has yet to come for another 3 weeks, and in the mean time, I'm training up for my SS legs on my 26FS Geared. I have not had the chance to ride SS to feel the difference as I will, surprisingly, be the pioneer for both SS and 29er for my LBS. Because I am the pioneer, my LBS (and other nearby LBS's) do not stock up on SS components.

    The mission here is to determine what cogs I need depending on the terrain and fitness. As I have a general idea what I need on a 26FS Geared, I would like to know if there are any translations needed to the 29SS Rigid.

    I've calculated gear-inches with Sheldon Brown's SS Calculator to find the difference in ratios between 29er and 26er wheels. They are as follows:

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    Basically, as mentioned before in this forum, the 29er needs to move down one cog level not teeth to somewhat match the 26er, ie. 16T cog on a 26er gives roughly the same gear-inches as a 29er with 18T cog.

    Aside from the technical and objective calculations above, as I am riding a 26FS Geared, there should be a some differences in efficiency and power transfer between a 26FS Geared and 29SS Rigid. I've itemized the comparisons below:

    1) 26 vs. 29. This can be determined objectively with Sheldon Brown's calculator.

    2) Geared vs. SS. I understand from the forum that the bike will be easier to pedal as there is no derailleur to supply additional chain travel and, hence, friction.

    Will the removal of a derailleur on an SS give the bike a subjective feeling of being on a larger cog? Eg., say I run 32:16 on 26er Geared, will the removal of the derailleur make it feel like a 32:17 or 32:18?

    Ok, I'm lazy. I can easily take my derailleur off and run my 26FS Geared as SS. I haven't shifted my FD since training, but I still shift my RD to determine ideal cogs for specific situations. If I convert to SS, then I will also have to shorten my chain, get an EBB, etc., etc. I would like to keep my 26FS geared and on standby.

    3) FS vs. HT/Rigid. Can the difference of power transfer between a HT and FS be subjectively equated to a increase/decrease in cog size?


    Perhaps there is no subjective difference in feel for any translation between 26FS and 29SS and if so, that will also help me choose the right cog(s).

    I could not be cheap and order the full spectrum of cogs and test each one once my SS bike comes but isn't it a waste of money to buy what is not needed? Plus, why not tap into this vast resource of SS knowledge and experience?

  2. #2
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    My suggestion for the 29 ss, is 32 20. I have tried an 18 on the rear, and found its great for the average trail, with little tech riding. The climbs are tough on the 18.. so I settled on a 20, because I like tech riding, and enjoy the extra leverage. I would suggest you keep a 20 on hand, and an 18 for the easier trails. I also have a 22 for extended climbs out west. It seems like the 2 tooth difference, has the most impact. I tried a 19 as well.. but it was barely any different than the 18. Here is the way I see it, I would rather spin out on the flats, than push uphill. You cant have it both ways. So that is why I keep the 2 tooth cog difference in my pack, for traveling to new trails.
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    Also, keep this in mind, when swapping cogs, going 3 tooth sizes either way, will warrant either adding links to the chain, or removing them. I carry an extra chain and links in my pack. Most bikes have enough adjustment for 2 tooth swaps, be it EBB, or Paragon sliders, which I have.
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  4. #4
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    Quote Originally Posted by mo0se
    Also, keep this in mind, when swapping cogs, going 3 tooth sizes either way, will warrant either adding links to the chain, or removing them. I carry an extra chain and links in my pack. Most bikes have enough adjustment for 2 tooth swaps, be it EBB, or Paragon sliders, which I have.
    My Karate Money can go from an 18 to a 22 with the same chain.

  5. #5
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    I think a lot of it depends on how short the chain is that comes on the bike.
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  6. #6
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    I "practiced" on my 26 FS for a while before pulling the trigger on my 29 SS rigid. I typically rode in 32/20 on the FS bike.

    I agree with mo0se on his general observations. My 29 came with 32/18. Which was great for riding on the street. But was a bit too fast for the trails. So I knocked it down a notch to a 20t and it just felt so right.

    So I'm running 32/20 on the rigid 29.

    I'm sure there are some efficiencies with not having a derailuer and shorter chain and all. Plus my SS bike is about 4# lighter than my FS/geared 26. And lastly, when I encounter a slight hill, I'm out of the saddle. The squish I feel when pedaling out of the saddle on my FS bike actually comes more from my front than my rear. Hence, I get more forward motion for my out of saddle efforts on the rigid. Plus there is the whole levitating your body over the rough stuff and letting the bike dance under you while you continue to pedal and step out that drops your riding buddy's jaw as you pull away from them thing.
    Just get out and ride!

  7. #7
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    the general rule with a 32 up front is to add 2 teeth to the rear for 26" to 29" 32x16 (26") = 32x18 (29er). The choice gearing is all personal preference, 32x18 is the general starting point. I run 32x18 most of the time. You will find what works for you and your area. Enjoy the SS, my 29er SS is the funnest bike I own!

  8. #8
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    Quote Originally Posted by mo0se
    My suggestion for the 29 ss, is 32 20.
    I have 32x19 on mine, but recently, an SS'er that I respect and who is very fast, says he just switched to 32x20 and is loving it. I'm considering it.
    :wq

  9. #9
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    I run a 34*16 on my SS for racing. In races with more climbing I use a 32*16.

    I ride a 26er.
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  10. #10
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    There really is no way to be completely sure until you try it. I found the perfect gear for me and my 29er to be 32/21. If you ride trails that are pretty much up and down with very few long flat sections, I think either a 20 or 21 tooth cog is a good starting point.

  11. #11
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    I just rode an up and down mountain trail on my 26FS Geared set to 32:18, and it feels like a good combination with good enough speed on flats and not too tough mashing on uphills. That should be equivalent to 32:20 on a 29er.

    So I can safely assume the derailleur and rear suspension will not affect the transation?

  12. #12
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    Quote Originally Posted by hchchch
    I just rode an up and down mountain trail on my 26FS Geared set to 32:18, and it feels like a good combination with good enough speed on flats and not too tough mashing on uphills. That should be equivalent to 32:20 on a 29er.

    So I can safely assume the derailleur and rear suspension will not affect the transation?
    I think maybe the suspension, and all the extra weight are not painting you an accurate picture. I think once the bike is built, and you are able to hit the trails, you will be pleasantly surprised. :-)
    The only regrets in life, are the risks you didn't take.

  13. #13
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    Quote Originally Posted by Thor29
    I found the perfect gear for me and my 29er to be 32/21. If you ride trails that are pretty much up and down with very few long flat sections, I think either a 20 or 21 tooth cog is a good starting point.
    +1 to that

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