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R5 post clamp failure

Last post 07-20-2018 9:10 AM by bobcdc. 14 replies.
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  • 01-12-2015 7:32 PM

    R5 post clamp failure

    I've just broken a clamp half way up a 30km climb on my 2015 R5. Anyone else had an issue? Initially had post slippage probs, but sandpaper and the usual cabin past fixed that. At 6nm it's torn the alloy thread from clamp. To make do for the week I've put thru a bolt,,, hopefully that will last as I'm in the middle of no where!
  • 01-12-2015 10:36 PM In reply to

    • goodboyr
    • Top 10 Contributor
    • Joined on 08-16-2007
    • Thornhill, Ontario
    • Posts 964

    Re: R5 post clamp failure

    6 NM is max. Given tolerances I would never torque a bolt to its max. PS. I think I've beaten EM3 to a comment he always makes! :-)
    Bobbo
    2015 COR
    '06 R3, Fully Internal Dura Ace 7970, Zipp 303FC Clinchers
    S5 Team, Ultegra Di2, Zipp 101
    RCA 56cm, Dura Ace 9070, Zipp 404 FC Tubbies

  • 01-13-2015 1:31 AM In reply to

    Re: R5 post clamp failure

    Agreed.... But unfortunately, with carbon paste, and 5nm it would slip an inch in a descent... So roughed up the post with sandpaper and added more carbon paste and slippage was still occurring at 5nm. So I torqued it to 6nm and it slipped and failed at 10km into a climb. Day 2 of 7 riding in the Victorian Alps so hopefully my MacGuyver'ed fix will hold til I'm home.
  • 01-13-2015 1:45 AM In reply to

    Re: R5 post clamp failure

    thanks goodboyr...I will spare Harry the broken record lecture about proper torque because we both know he knows better :) Harry, if your post ain't holding at 6 Nm (especially with carbon paste applied) then the tolerances of either of your frame or post, are not correct. Cervelo will replace the clamp for you (the R5 seatpost clamp with squared back edges was Cervelo-specific on earlier R5 frames, not sure if still the case with new aero 2014/15 R5), but you will definitely want to try another seatpost to rule out one thing at a time. If a new seatpost slips again then I would definitely take the issue up with Cervelo. Good luck, EM3
  • 01-13-2015 1:51 AM In reply to

    Re: R5 post clamp failure

    eddymerckx3:
    thanks goodboyr...I will spare Harry the broken record lecture about proper torque because we both know he knows better :) Harry, if your post ain't holding at 6 Nm (especially with carbon paste applied) then the tolerances of either of your frame or post, are not correct. Cervelo will replace the clamp for you (the R5 seatpost clamp with squared back edges was Cervelo-specific on earlier R5 frames, not sure if still the case with new aero 2014/15 R5), but you will definitely want to try another seatpost to rule out one thing at a time. If a new seatpost slips again then I would definitely take the issue up with Cervelo. Good luck, EM3
    Thanks EM3, So far so good, the current arrangement held up on the 30km climb later that day. The post was being replaced with a 3T post anyways so I'll see how that goes when it arrives. I've scuffed up the factory FSA post that much that I'd be replacing it anyways. The squared off Seatpost clamp still remains on the 2015 edition, hence my spare generic one I brought with me in my toolbox was useless! Maybe this is just a way of making me aware that at 80kgs I'm a bit heavy!
  • 01-13-2015 5:37 PM In reply to

    Re: R5 post clamp failure

    good luck...b sure not to scrape/sand the new seatpost after you install the new clamp. Roughing-up the seatpost won't really get you more purchase if the diameter of the seatpost or ID of seat tube is off (in fact it might get you less purchase as you will have removed material)....besides most carbon paste is fairly tacky and the micro silicon pebbles should fill in the gap needed to get firm grip.EM3
  • 01-13-2015 9:24 PM In reply to

    • levi
    • Top 50 Contributor
    • Joined on 08-27-2010
    • Posts 373

    Re: R5 post clamp failure

    I remembered Enve had problems with their seatpost out of spec. Measure the OD of the seatpost using a good caliper. 9 out of 10 it is the seatpost and not the frame that is out of spec.
  • 01-14-2015 4:55 AM In reply to

    Re: R5 post clamp failure

    I'll measure up the FSA post when I get home...
  • 03-18-2015 11:11 PM In reply to

    Re: R5 post clamp failure

    Bit of a thread dig/update Stock FSA post measured at 27.05 to 27.1mm so I smidge under spec.... I swapped it for a within spec 27.2 3T post, but still experienced some slippage even when clamp was torqued to 5 to 6nm. I then swapped to an ENVE post, but this still slips unless I over-torque the clamp. So... Is anyone else experiencing slipping issues... I've just resorted to over torquing the modded seat lamp, which clearly isn't ideal....
  • 03-19-2015 10:12 AM In reply to

    Re: R5 post clamp failure

    What is the length of the seat post insertion into the seat tube? If too short, that can break the clamp. Get a post that's 200mm insertion.

  • 03-19-2015 10:46 AM In reply to

    Re: R5 post clamp failure

    Ctopher:

    What is the length of the seat post insertion into the seat tube? If too short, that can break the clamp. Get a post that's 200mm insertion.

    The clamp failed by stripping it's internal thread while riding up one of the bigger climbs here in Australia.... Although, not probably an issue, the stock FSA post at the time had copious amounts of post in the frame.... Not exactly sure how much but it would've been in excess of 150 to 200mm....
  • 03-19-2015 12:49 PM In reply to

    Re: R5 post clamp failure

    Harry, it sounds like you have a great set of calipers....have u measured the ID of the seattube? I suspect the ID might not be to spec if u r still experiencing slippage with several different posts. It sounds like u have done your due diligence and now its time for Cevelo to replace ur frame. EM3
  • 03-23-2015 10:18 AM In reply to

    Re: R5 post clamp failure

     Thanks EM3,

    WRT to measuring the ID of the seat tube, I can make this ID anything I want by tightening the clamp. Im assuming u mean measuring its ID without the clamp installed?

    cheers 

  • 03-23-2015 11:24 AM In reply to

    Re: R5 post clamp failure

    HarryVolmer:
    Im assuming u mean measuring its ID without the clamp installed?

    cheers 

    ...yes, precisely, w/out the clamp installed it should measure to 27.2 or max or 27.3....I suspect urs will probably be closer to 27.4 or 27.5. If so then I would definitely encourage u to pursue a warranty exchange. Good luck. EM3
  • 07-20-2018 9:10 AM In reply to

    Re: R5 post clamp failure

    I realize this is an older post but thought I'd respond. I had my clamp fail now for the second time. I always torque it less than 6 nm. I find the clamps last about 2.5 years. It's a poor design by Cervelo. Love the bike otherwise. Bob
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