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  1. #1
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    1x12 swap, missing the top end.

    I did a SRAM NX swap on my old Raleigh M-80, so far I知 loving it. Just one thing-when I知 on the black top or going downhill, I am missing some top end. I know I could push harder if I had an extra gear. What is the tweak? Larger crank ring?





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    I race XC with a 2005 Raleigh M80. Yes, I really do.

  2. #2
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    Yeah, you have acres of room there for a bigger chainring.
    whatever...

  3. #3
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    Quote Originally Posted by steadite View Post
    Yeah, you have acres of room there for a bigger chainring.
    How do I calculate what size chainring I may need?
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  4. #4
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    Quote Originally Posted by HotelBravo26 View Post
    How do I calculate what size chainring I may need?
    If you're used to what you have on there now, just go up one size. So, if you're currently at 30t, just go up to 32t, for example. Two teeth make a difference. Your legs will tell you so. Also, you may need a new chain if you go larger, just be aware of that.

  5. #5
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    Yes, my legs are telling me. That is how I know I'm missing the top end. I found this calculator: https://sheldonbrown.com/gear-calc.html

    The groupset came with a 32t chainring. I compared the Gain Ratio's for the NX groupset on my bike versus on a 29er with the Gain Ratios for my wheel diameter, then toggled the chainring size up. The Gain Ratio tables seem to normalize for my wheel size when the chanring is 35t, 36t would be the closest to the same numbers as if I were running the 32t on the 29er.


    26" wheel 30t front, 11t back = 5.1 Gain Ratio WHAT I HAVE

    29" wheel 30t front, 11t back = 5.7 Gain Ratio WHAT THE DONOR WAS

    29" wheel 32t front, 11t back = 6.1 Gain Ratio WHAT I AM TARGETING

    26" wheel 32t front, 11t back = 5.5 Gain Ratio

    26" wheel 34t front, 11t back = 5.8 Gain Ratio

    26" wheel 36t front, 11t back = 6.2 Gain Ratio WHAT I NEED

    Seems like the 36t would be the best fit for my application?

    UPDATE: I actually have a 30t front ring, which puts my gain ratio at 5.1 - It would be a 5.7 on the 29er Stump Jumper it came off of. Still, the Epic (which is a Cross Country MTB closer to spec for my intented use) uses the 32t. So if I wanted to keep the same Gain Ratios as the trail, I'd go 34t. If I want to gear the bike to match specs foe XC racing I'd go 36t in front. Make sense?
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  6. #6
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    Here are the exact Gain Ratios I will have once the race wheelset and the current cassette in place with a 36t Chainring:

    1x12 swap, missing the top end.-gainratiochart26_235_36t_eaglenx.jpg


    Here are the Gain Ratios from an EAGLE GX (or better) Equiped 29er.

    1x12 swap, missing the top end.-grainratio_29w_2.3_32t_eagle-gx.jpg
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  7. #7
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    I prefer gear inches for something like this. Easier to process in my mind. I pedal XYZ gear and I go XYZ distance.
    Silly bike things happening.

  8. #8
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    Quote Originally Posted by Redlands R&C View Post
    I prefer gear inches for something like this. Easier to process in my mind. I pedal XYZ gear and I go XYZ distance.
    Here they are in Gear Inches:

    26er with 36t Chainring and Eagle NX Cassette-




    29er with 32t Chainring and Eagle GX Cassette-



    Here is how the bike is setup right now:



    Thanks for taking a look.
    Attached Thumbnails Attached Thumbnails 1x12 swap, missing the top end.-gear_inches_chart26w_2.35_36t_eaglenx.jpg  

    1x12 swap, missing the top end.-gear_inches_29w_2.3_32t_eagle-gx.jpg  

    1x12 swap, missing the top end.-gear_inches_chart26w_2.125_30t_eaglenx.jpg  

    I race XC with a 2005 Raleigh M80. Yes, I really do.

  9. #9
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    Are you comparing the feeling of this bike with the upgrade to how it rode before you switched to 1x12 (I'm assuming it was 3x9?) Or are you trying to replicate the feel of another bike, since you mentioned a couple 29" bikes?

    If you were on a 3x setup before, try to compare the gear inch range of the triple with what the 1x has. It has been aaaage's since I rode a 26" with a 1x, but at that time I had a 36T ring and I wanted a bigger gear, so I'd lean (without more info) to at least a 36T.
    Silly bike things happening.

  10. #10
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    Quote Originally Posted by Redlands R&C View Post
    I prefer gear inches for something like this. Easier to process in my mind. I pedal XYZ gear and I go XYZ distance.
    Shoot, a 38t Chainring might actually be the most useful, check out the numbers compared to the 29er:

    1x12 swap, missing the top end.-gear_inches_chart26w_2.35_38t_eaglenx.jpg
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  11. #11
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    Quote Originally Posted by Redlands R&C View Post
    Are you comparing the feeling of this bike with the upgrade to how it rode before you switched to 1x12 (I'm assuming it was 3x9?) Or are you trying to replicate the feel of another bike, since you mentioned a couple 29" bikes?

    If you were on a 3x setup before, try to compare the gear inch range of the triple with what the 1x has. It has been aaaage's since I rode a 26" with a 1x, but at that time I had a 36T ring and I wanted a bigger gear, so I'd lean (without more info) to at least a 36T.
    I am benching marking it against modern 29er XC bikes, this is a comparision to the drivetrain setup found on a Specialized Epic, for instance. Running the numbers, I 38t may even be the best option. Check out the charts. What do you think?
    I race XC with a 2005 Raleigh M80. Yes, I really do.

  12. #12
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    Looks pretty close. If you want to do it on the cheapy cheap, try to find one of those stamped steel SRAM chainrings, that way if it is too big or not what you are after, you aren't out a lot of money. At least you are headed in the right direction! Thats the fun of upgrading, try and try again until you get it! (or run out of money...)
    Silly bike things happening.

  13. #13
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    I知 going to start with the 36t and train with that. If I find I need more, I値l go to the 38t later in the year.


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    I race XC with a 2005 Raleigh M80. Yes, I really do.

  14. #14
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    The 36t is working nicely so far. I also like the GX chain compared to the stock NX.

    One other note, for others who may be shopping takeoffs for a budget build- the 30t chainring that came off was for a boost BB, definitely explained some of the bottom limit calibration problems I was experiencing. Now, smooth as butter in all weather.

    Next stop, new wheel set is being built.


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    I race XC with a 2005 Raleigh M80. Yes, I really do.

  15. #15
    Rod
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    Quote Originally Posted by HotelBravo26 View Post
    The 36t is working nicely so far. I also like the GX chain compared to the stock NX.

    One other note, for others who may be shopping takeoffs for a budget build- the 30t chainring that came off was for a boost BB, definitely explained some of the bottom limit calibration problems I was experiencing. Now, smooth as butter in all weather.

    Next stop, new wheel set is being built.


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    In my area, most people gear down and remove the stock 32 tooth front ring for a 28 or 30.

    For anyone else who may see this at 87.5 gear inches, 29x2.35 tires with 30x10, I can cruise at 24 mph on my way to the trailhead. Unless it's a downhill sprint, this is more than adequate. This is between the 36x11 and 38x11 on a 26er, which is exactly what the OP put on his bike. Gives plenty of low end without sacrificing your top speed.

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