11sp, 29r's, gear ratios and all that….

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  • 11sp, 29r's, gear ratios and all that….
  • Premier Icon mikewsmith
    Subscriber

    Right then, the missus is looking at the racier bike market and looking at 100mm FS. (Not going to add the bike to the debate…)
    Looking at Frame only vs Built with some key requirements – No Shimano Drivetrain. She currently has X0/X9 combo on Race Face Next cranks/XX cassette which is good. The crankset is the 24/38 one, previously she has had 3x and 2x with 32t max though she is getting used to the 38 up front.

    To add in some more she had a Rocky Mountain Element on demo which she liked, I had a bit of a spin on it, the thing that struck me was I was running lower gears than I expected – is this normal? Do you run a lower gear on 29 than 26?

    Moving to the build, she is looking at the XO1 and some of the online calcs have the range on a 30/32 being most of that of a the good part of a 24/38 setup.

    Sound about right any experiences? This is going to be her multi day race bike, so considering having a couple of spare chain rings to swap out for any major climbing or flat out fire road stages.

    Plan B the XO1 and put it on her trail bike and move the other stuff over.
    Plan C move the 2x over and replace with normal SRAM stuff…

    Comments please but following the rules…
    No Shimano vs Sram stuff
    No Why not get a 3x/I don’t see the point of 1x/ Oh isn’t is all a bit flash….
    Thanks

    Premier Icon njee20
    Subscriber

    You can’t fit a 30t ring to X01 as it’s a standard 104mm BCD – have to get XX1 cranks to go smaller than 32t. Gear down slightly (about 10%) on a 29er. But yes, a 32t ring would ‘cost’ you the top and bottom gears only from the 2×10 setup.

    Premier Icon mikewsmith
    Subscriber

    Cheers, the current spec says you can get the 30t on it but not the 28.
    http://www.sram.com/sram/mountain/products/sram-x01-crankset
    Sounds like a reasonable range though

    Does she spend a lot of time in the 24/36 combo currently? I’d argue that unless she does then it might be better to go 30t to save running around on the smaller rear sprockets in the majority of the time.

    I had this issue with Mrs BS on her new Anthem 29. decided to go with a 32t front as she NEVER used the inner ring on her 3×10 and barely ever the 28t on her 2×10 around where we ride.

    Premier Icon njee20
    Subscriber

    Cheers, the current spec says you can get the 30t on it but not the 28.

    Aah yes, they’re obviously using offset 30t rings. Alternatively just look at the XX1 chainset, not much in it price wise.

    Premier Icon mikewsmith
    Subscriber

    Does she spend a lot of time in the 24/36 combo currently?

    What a question, would you mind asking for me 😉
    Her current thoughts were she will have a go with what comes and we can drop the front is needed. We have some fairly grim hills round here but the bike will be lighter and as it’s a 29r powered by magic….

    just need to check out the 94bcd options… anyone seen how that works? They seem to be speccing 94 & 104 BCD cranks

    Premier Icon mikewsmith
    Subscriber

    Aah yes, they’re obviously using offset 30t rings. Alternatively just look at the XX1 chainset, not much in it price wise.

    Standalone it’s not but as part of a build kit it is eye watering due to all the other “upgrades” that are included

    What a question, would you mind asking for me

    Haha, I know what you mean. Mrs BS wouldn’t use the little ring previously, not because she was amazingly strong and never needed low gearing, but because she’s a stubborn cow who would rather walk than ride slowly?!?

    Premier Icon mikewsmith
    Subscriber

    different issue here, “how often do you use that gear” – how would I know…. at least it will stop chain crossing

    stevego
    Member

    I’ve recently moved from a 26-er to a 29-er (anthem X to a Scalpel-1). Although the new bike is over a kg lighter it doesn’t sem to climb quite as well as the anthem (I was surprised). Whether this is due to gearing (both are 2 X 10), geo differences, differences in my fitness/perception or the way I pedal on uphills I’m not sure. The new bike is much faster on the flats and descents though, overall I average about 5-10% faster over a similar loop.

    Premier Icon ratherbeintobago
    Subscriber

    To add in some more she had a Rocky Mountain Element on demo which she liked, I had a bit of a spin on it, the thing that struck me was I was running lower gears than I expected – is this normal? Do you run a lower gear on 29 than 26?

    Have you added the ‘fudge factor’ of about 10% to the 29er ratios to compensate for the bigger wheel?

    Premier Icon mikewsmith
    Subscriber

    Have you added the ‘fudge factor’ of about 10% to the 29er ratios to compensate for the bigger wheel?

    Having never ridden one before I had no real idea, but yes it feels like 10%

    olie
    Member

    I’m riding a Zesty TR 729 with XO1 and a 30T front ring.

    I think that the 30T is great for very hilly areas or certain races with loads of climbing or “attrition” races such as stage races. But you soon run out of gears on faster flats or downs. I’ll probably go to a 32T and new chain so I can flip between 30/32/34 depending on where I’m racing without worrying about chain length.

    Of course the TR is hardly a race bike so more info when my hard tail arives!

    The gear table should take into account wheel size as you divide all the numbers by the wheels size anyway to get a true representation of gear inches.

    coopersport1
    Member

    Bung it all in here if you want to see the diff wheel size makes to various ratios http://sheldonbrown.com/gears/

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