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  1. #1
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    180mm cranks better on 29r?

    Hi I'm thinking about going with 180mm cranks on my new 29r
    I'm thinking with the higher bb = more ground clearance and bigger
    Wheels may work better with more leverage.
    My only problem is finding a set I need BB30 cranks and cannot find
    Any anywhere on the net does anybody know of any?

    Thanks

  2. #2
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    How much higher bottom bracket? Do you have measurements?
    Are you a taller rider? Are you a heavier rider? What type of riding are you doing?

    We can't answer whether it is "better" or not without knowing more.

  3. #3
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    I guess it depends on the bike. My anthem has a low bb height, for a 29er. I didn't think it would matter much but my 175's are pedal striking like crazy. I'm thinking of going to 170's. Working my timing as well.
    Small ring in front makes it easier. Small ring in back makes it harder. That blows my mind.

  4. #4
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by danza View Post
    Hi I'm thinking about going with 180mm cranks on my new 29r
    I'm thinking with the higher bb = more ground clearance and bigger
    Wheels may work better with more leverage.
    My only problem is finding a set I need BB30 cranks and cannot find
    Any anywhere on the net does anybody know of any?

    Thanks
    Crank length is not affected by wheel size. It is rider preference.

    While it varies from bike model to model, 29ers do not have higher BBs than a similar model 26er. The frame geometry is adjusted (more BB drop) to keep the BB ht about the same.

    Wheels Manufacturing and Enduro Bearing make adaptors to use 24mm spindle cranks in BB30 frames.
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  5. #5
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    Every time I get new cranks I tell myself to go big or go home and get 180s. So I found XTR doubles on Jenson at 180 for $300 and jumped on them. Seemed like a great idea, but my highball and its 12" BB height has different ideas.... It pedal strikes like crazy on almost any rock in the vicinity of my line. Oh well I think I can tell a power difference and I certainly can torque the crap out of them. I dont know what the magic bb height is to make 180s work without leaving sparks at every rock garden but I'd bet its over 13".

  6. #6
    KgB
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    I used to run 180's on my SS years ago because the extra leverage argument seemed to make sense. Now I understand that leg length and personal preference are more important. I have 170's on all my bikes. shorter cranks = smoother spin for me.
    I've been inside too long.

  7. #7
    ballbuster
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    No difference

    Quote Originally Posted by danza View Post
    Hi I'm thinking about going with 180mm cranks on my new 29r
    I'm thinking with the higher bb = more ground clearance and bigger
    Wheels may work better with more leverage.
    My only problem is finding a set I need BB30 cranks and cannot find
    Any anywhere on the net does anybody know of any?

    Thanks

    29ers don't have a higher bottom bracket. They generally have longer chain stays to make room for the bigger rear wheel in the frame, but that is the only real difference between 26ers and 29ers. Also, HA is generally a tad slacker, and more fork rake to make up for it. The amounts aren't that wildly different, tho.

    If you liked 180s before, you'll like them on a 29er just the same, unless somehow the bigger wheels make your legs longer, or something.

    And really, 180s don't give you a crapmore leverage over 175s. It's a bit, but really not much. I switched to 180s because I liked the feel. Somehow, they seemed easier on my knees.

    Most folks my size (5'10", 33" pant inseam) would run 175s. I ran 175s for years, and went to 180s on my singlespeed, just to check them out. I dug them, so I got 180s for all my bikes. YMMV.

    Heh... also, on my road/cross bike, I went to 175s. I had 170s and 172.5s, but they always felt like spinning kiddie cranks.

    Also, I'm of the opinion that if you're pedal striking 180s, you would probably pedal strike on 175s, but not blame the cranks. Think about it: put your fingers apart and measure 5mm. It's really a small amount. If you're pedal striking, don't blame the cranks or the BB height. Blame the rider. It's not that hard to time your cranks so they miss rocks and stuff. Learn to pedal better.

    If you're 180 curious, find a set of used XTs or XTRs and try them out. If you hate them, you can flip them on craigslist for what you paid.
    Last edited by pimpbot; 10-22-2012 at 08:42 PM.

  8. #8
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    180mm cranks should be used by people with long legs (long femurs) who are definitely on the tall side. It is a fit question, nothing else. There are benefits, that said. Also pedal strikes on the downside.

    I am on 180 XT 2x10 (26/38) cranks on a 29er. (Bike came with 175 cranks) But I am tall with long legs. It fits me. But I did have to change my pedal cadence through tall rocky sections. It did allow me to lower my saddle 5mm and bring it forward another 5mm. The extra 1 cm length overall translates into a slightly wider plate form while descending, which is great. They offer a small amount of extra torque as well. But you will have to be strong and fit to get to use that extra grunt.

  9. #9
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    It's easier for me to pull slow climbs on 180's over 175's. Pedal stikes were not an issue as my bikes do not adhere to the new lower is better standard (13.7"BB height on both my bikes) I rode 175's for years and thought 5mm "ain't nuthin" well I put 175's on my last build and they were off after a few rides.

  10. #10
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    if your worried about pedal strikes try a high poe rear hub, it will help your timing (no slop in engagement) at least it did for me!
    “An adventure is misery and discomfort, relived in the safety of reminiscence.” Marco Polo

  11. #11
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    I like 180s on my single speed 29er because I spend a lot more time at low RPM mashing up hills than I do spinning high RPM. But on geared bikes I stick to 175mm cranks. On my single speed road bike, I have 170mm cranks. The difference between each length crank is pretty subtle.

    But anyway, wheel size has nothing to do with crank length. I personally don't feel like leg length matters much either. To me it is all about RPM - high speed spinning is easier on a shorter crank and low speed mashing is easier on a longer crank.

  12. #12
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    There is a proper relationship between seat height, seat fore and aft position, and pedal/cleat position. Sometimes crank length becomes part of this equation or at least it can. If your are tall, it will. A proper fit will have the hips sitting on the seat without any rocking movement through crank rotation. A plumb line should drop directly from the face of the tibial plateau to a point on the top of the foot just above where the cleat attaches to the petal with the crank arms sitting parallel to the floor. A longer 180 crank arm allows the seat height to be dropped by 5mm and moved 5mm forward from a 175 set. This lowers the CG as well as puts slightly more weight forward, which can be good as well while seated.

    Pedal speed through the crank revolution will increase as the arms increase in length. However, it is not by much mathematically.

  13. #13
    turtles make me hot
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    My bike originally came with 175mm cranks and an 11-34 cassette. Identical to the parts that were on my buddy's 26er. Made no sense to me. I swapped to 180's and to an 11-36 cassette. Bike has a much more useable range on the middle ring.
    I like turtles

  14. #14
    Burnt Orange Lives
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    no, not at all... stick with what you have been using... 175 most likely... i've seen some singlespeed guys running 180, but no need on 29er or any other bike UNLESS you have 24+ inseam... even then probably not..

  15. #15
    Burnt Orange Lives
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    Quote Originally Posted by shiggy View Post

    Wheels Manufacturing and Enduro Bearing make adaptors to use 24mm spindle cranks in BB30 frames.
    i have Enduro one. it works perfectly well and is not adding too much weight... pm me if you don't find one - i can sell you mine...

  16. #16
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    I've found a happy spot with 180mm cranks on my MTB and CX. I run 175s on the road bike and can't really tell much of a difference in the spin. The reduced Q-factor from my MTB is more noticeable than the 5mm shorter crank arms.
    Happiness depends more on the inward disposition of mind than on outward circumstances. Benjamin Franklin

  17. #17
    Ride da mOOn Moderator
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    Good job!

    Better?

    Absolutely... if your tall, and/or have long legs and/or have weight to power them! Pedal strikes are caused by your own mistiming, If I see a pedal strike lined up on a rock, I just ratchet a bit and miss the rock...

    ...or smash the s88t out of it...LOL

    I run ol'school Redline BMX Cromo cranks, 185mm on my Redline Monocog SSer 26er with higher gearing 39/16 and love the feel, just drop the hammer and the bike leaps forward!
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  18. #18
    Future Primative
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    I agree, pedal strike is all from riding with a crank arm in the 6 o'clock postion. I understand if you've been in the saddle a long time and fatigue is to blame. Learn to time your cranking better and stop riding like a roadie. Learn to ride a more "moto-style" and enjoy!

  19. #19
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    Strikes and Jack just happens occasionally, usually when you DONT expect it.....no matter how bad ass "moto" you are....especially if you ride technical terrain and not just swooping around with your pedals "clocked" properly....

    Im 6'4" (34" inseam) and run 180's. I think the pedal jack and strikes may outweigh the slight benefit (if any) of the 5mm or so crank length...I am thinking of getting some E13 cranks and would probably go back to the 175's just for this reason...

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