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  1. #1
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    Sram Rival Crank Failure

    Just riding along....



    Charging up a hill and it just let go. I almost went down, but I saved it. Crank is from 2011 and the pedal was heavily greased, but I may have used titanium grease since I was building up the bike and thought I should just use up the syringe of stuff...hence the reddish color you see on the threads. Bike is a commuter and is ridden year round in Seattle, so it does get ridden in the rain.

    New crank on order....

  2. #2
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    Were your pedals installed with pedal washers against the crankarms?

  3. #3
    'brifter' is a lame word.
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    I'm pretty sure the red I see is rust. Anti-seize comes in copper (oddly enough copper colored) or the silver stuff. Not rust colored. Maybe a close up photo?
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  4. #4
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    Yep, pedal washers installed. (the u-shaped piece is backwards in orientation in the photo...it should be flipped around). So, the rust is against the washer.



    Last edited by bike867; 08-27-2018 at 06:57 PM.

  5. #5
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    Yep, rust.

    Looks like there was a crack for some time (different color metal in failure, rust stain inside part of failure) and recently gave up the rest of the way.

    So, jra after your failure to recognize a failing part for some amount of time. And "charging up a hill" =/= jra.
    Last edited by crit_boy; 08-27-2018 at 07:03 PM.

  6. #6
    'brifter' is a lame word.
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    Quote Originally Posted by crit_boy View Post
    Yep, rust.

    Looks like there was a crack for some time (different color metal in failure, rust stain inside part of failure) and recently gave up the rest of the way.

    So, jra after your failure to recognize a failing part for some amount of time. And "charging up a hill" =/= jra.
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  7. #7
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    Yikes! I've seen sheared cranks, but not at the pedal threads. They sure look dry to me. "Heavily greased" when?

    I've always used the white grease on most of my threads including pedals. Would anti-seize be better?
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

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  8. #8
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    Sram Rival Crank Failure

    Grease or whatever isn't going to help much, although if it prevents corrosion it might. Looks like the OP's crank had corrosion. Corrosion could cause a crack and cause it to propagate faster.

    Typical fatigue failure of a crank at the pedal eye is primarily caused by a poorly designed joint. Jobst Brandt found that a conical interface at the pedal attachment prevents the failure. Component companies didn't want to change. Mostly it occurs on high mileage cranks.

    It's good to inspect your cranks for cracks at the pedal eye. I found one on my cranks before it propagated too far. I broke another crank on a climb standing out of the saddle on a steep grade. It happens.

    https://www.sheldonbrown.com/brandt/...ng-cranks.html
    Last edited by mfdemicco; 08-28-2018 at 08:14 AM.

  9. #9
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    Quote Originally Posted by mfdemicco View Post

    It's good to inspect your cranks for cracks at the pedal eye. I found one on my cranks before it propagated too far. I broke another crank on a climb standing out of the saddle on a steep grade. It happens.

    Noted. Having one go on the road is something I'd like to avoid. And I never thought to look for cracks.

    Out of curiosity what cranks did you crack/break?

  10. #10
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    So, we're saying one should remove the pedal and inspect the pedal eye area for cracks and/or corrosion every season? That's not something I've done, of course. These pedals were installed 7 years ago and have roughly 18k miles on them. I'm sure any grease I put on them "back in the day" washed out ages ago.

  11. #11
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    Quote Originally Posted by Jay Strongbow View Post
    Noted. Having one go on the road is something I'd like to avoid. And I never thought to look for cracks.

    Out of curiosity what cranks did you crack/break?
    Shimano 105 and Ultegra triple cranks.

  12. #12
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    Quote Originally Posted by bike867 View Post
    So, we're saying one should remove the pedal and inspect the pedal eye area for cracks and/or corrosion every season? That's not something I've done, of course. These pedals were installed 7 years ago and have roughly 18k miles on them. I'm sure any grease I put on them "back in the day" washed out ages ago.
    I saw a crack on the back side of the crank. You should be able to see cracks without removing the pedals on a clean crank. I try to inspect everytime I wash my bike.

  13. #13
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    Quote Originally Posted by mfdemicco View Post
    Shimano 105 and Ultegra triple cranks.
    I know your experience is an outlier but still, might have to re-think my assumptions that alloy is better than carbon for cranks.
    Carbon would pretty much eliminate corrosion and fatigue being the cause of breakage, I think.

  14. #14
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    Dunno if this was discussed here "back in the day"...but...

    failure shimano ultegra crank causes serious bicycle accident

    Was this just a bad batch of cranks or a design/production issue?

  15. #15
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    Quote Originally Posted by Jay Strongbow View Post
    I know your experience is an outlier but still, might have to re-think my assumptions that alloy is better than carbon for cranks.
    Carbon would pretty much eliminate corrosion and fatigue being the cause of breakage, I think.
    I don't know. A coworker was on a century and had to sag out because the threaded insert in his carbon crank came out.

  16. #16
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    That much excess cable would drive me nuts.
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  17. #17
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    Quote Originally Posted by craiger_ny View Post
    That much excess cable would drive me nuts.
    Heh, yeah. The cable end is also rubbing an arc into the frame.

    Sucks about the Rival crank, and that 6800 failure mode is crazy.

  18. #18
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    I'm surprised that with so many carbon bikes & parts out there in this day & age, people's definition of maintenance varies so much. I wash my rides every 2 weeks & that is a complete top to bottom wash, degreasing of drive train & then wax & lube. Takes 1 hour. End of season, everything gets stripped, cleaned, inspected & then rebuilt. I also ride in the winter & although more difficult, I still wash it as soon as possible after especially dirty rides.

    7 yrs of not removing the pedals off for any type of service is only asking for trouble. Especially if its a commuter bike that is ridden year round. I've never had any issues with the Rival cranks. They feel solid, shift well but are heavy. You should be able to pick up the Force carbon 10 speed cranks on the bay for a good price. Just make sure you get the gxp model. And no you don't use anti-seize on the threads unless its titanium axle on your pedals. Otherwise stick with grease.

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