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XT non drive side crank arm design, is it flawed?

qooqiiuqooqiiu Posts: 212
edited August 2012 in MTB workshop & tech
The reason i ask this is I've been having a little trouble with mine pretty much since day one.

It keeps coming loose.

Ive lost 2 crank caps now. I even bought a torque wrench so to tighten the 2 opposing bolts to the recommended 12/14 NM. I began by just judging them by hand...Today the arm once again worked its way loose. The plastic gasket and pin are correctly in place (are these even really necessary???) To top it off i have rounded the thread of one of the bolts now. Fortunately i found some high tensile bolts in the M6x20 which allow the Allen key to sit in much deeper so there's not much chance of rounding these ones.

I did these up to 25NM so if it comes loose again i'm going to ditch the XT in favour of something else. I note the XTR has a very different fastening method.

Anyone else had similar issues with their XT crank?

Posts

  • qooqiiuqooqiiu Posts: 212
    I just cant see the 2 opposing bolts clamping the arm strongly enough :(
  • Never had any problems.... Ever.

    And I've been running varieties of the Shimano HT2 setup for years.

    You are tightening the "crank cap" 1st and then the opposing bolts?
  • qooqiiuqooqiiu Posts: 212
    Hi,

    Yes, cap 1st then the bolts. I have to say that this is not what the shop did when it was set up leading the lose of my £7 anodised bolt from Hong Kong :cry:
  • nicklousenicklouse Posts: 50,675 Lives Here
    User error.

    It is the better design out there.

    XTR has the same basic design as do all shimano HT 2 cranks.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • qooqiiuqooqiiu Posts: 212
    I thought XTR has a single bolt that was supposed to be torqued to 45 NM which sounds a lot more substantial.
  • lesz42lesz42 Posts: 690
    user error or damaged , you cant see how 2 bolts are ok, yet no issues reported, in years ( unless its damaged or user error?)
    Giant Trance X0 (08) Reverb, Hope Hoops 5.1D, XT brakes, RQ BC, Works Components headset 1.5
  • Chunkers1980Chunkers1980 Posts: 8,035
    Shame about the red bolt. You must tighten the bolts equally and evenly working them both up bit by bit.
  • nicklousenicklouse Posts: 50,675 Lives Here
    qooqiiu wrote:
    I thought XTR has a single bolt that was supposed to be torqued to 45 NM which sounds a lot more substantial.
    XTR hollowtec 2 works just the same as any other HT 2 crankset so you thought wrong.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Dirtydog11Dirtydog11 Posts: 1,621
    I did these up to 25NM so if it comes loose again i'm going to ditch the XT


    I've fitted a few HT2 cranks and not had any come loose, however there was a chap on here a while back who had a similar issue.

    Buy some thread lock and re torque to 14nm. Tightening to 25NM is not the answer, I'm surprised you haven't stripped the threads.
  • nicklousenicklouse Posts: 50,675 Lives Here
    TBH the OP needs to look at how they are fitting the cranks.

    There will be something that they are doing fundamentally wrong.

    As the shimano design is the best functioning one for the external bearings. Nothing special is needed. Threadloack is not beeded. Over tightening is not needed.

    What does it say the tightening torque is for the pinch bolts? 12Nm. Nothing more is needed.

    And i should just correct a comment from earlier. Yes one of the XTR cranksets has a different fitting. Better? Hard to say.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • qooqiiuqooqiiu Posts: 212
    nicklouse wrote:
    .
    And i should just correct a comment from earlier. Yes one of the XTR cranksets has a different fitting. Better? Hard to say.

    So i didn't think wrong then. I thought right.
  • nicklousenicklouse Posts: 50,675 Lives Here
    Nope as you did not acrually say which XTR crankset as there is way more than one. And the 970 is not really "current" the current one 980 and 985 are just the same as all other HT2s

    Also back to your comment about it being flawed. If it was why is it used on all shimano current cranksets? Road and MTB and BMX?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • supersonicsupersonic Posts: 82,708 Lives Here
    Was the preload adjusted correctly on thre crank?
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    supersonic wrote:
    Was the preload adjusted correctly on thre crank?
    This is what I'm thinking.
    Something was done wrong, at least initially, if not continuously.
    Because of that, some damage occurred, and now the chainset is borked.
  • supersonicsupersonic Posts: 82,708 Lives Here
    I guess the other question is: right amount of BB spacers?
  • nicklousenicklouse Posts: 50,675 Lives Here
    And as the design is no different to the Aheadset system i ask is that flawed?

    BB faced?
    Correct number of spacers?
    Preload correct?
    Tightening the bolts correctly?

    If any one is not correct you will have issues.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • qooqiiuqooqiiu Posts: 212
    The bike is a 2012 Cube CTC pro. I had the shop changed the 2012 XT black crank for silver. I don't know what they did regarding spacers. I'm no expert. I know what i have done - and that is to remove the 2 bolts and then undo the crank cap screw the crank bolt back in (just hand tight using a cloth for a bit more purchase) then do up the 2 bolts using an Allen key, i did these up to 25NM.
  • qooqiiuqooqiiu Posts: 212
    It has always creaked a bit but i put this down to it being carbon???
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    qooqiiu wrote:
    The bike is a 2012 Cube CTC pro. I had the shop changed the 2012 XT black crank for silver. I don't know what they did regarding spacers. I'm no expert. I know what i have done - and that is to remove the 2 bolts and then undo the crank cap screw the crank bolt back in (just hand tight using a cloth for a bit more purchase) then do up the 2 bolts using an Allen key, i did these up to 25NM.
    Crank bolts? Crank caps?
    You're going to have to use the proper names if we're to understand what you mean.
    ALL manuals are on shimano's website, and they will also tell you how many spacers you need.
  • GiraffotoGiraffoto Posts: 2,078
    I fitted my first HT2 crankset for a mate about a week ago, so I reckon that makes me an expert**. The thing you're calling a "crank cap" may be a bit of plastic that you screw into the non drive side to get the right side-to-side pressure on the bearings. It doesn't do anything while you're riding, so in my definition it's a tool rather than a component. Use a torque wrench and do exactly what it says in the instructions, in the order it says it. Once you've got your crank bolts done up to the factory settings, put it away in the tool box and you won't lose it.


    **Note for real experts: I told him to take it to the LBS and get the bottom bracket faced first
    Specialized Roubaix Elite 2015
    XM-057 rigid 29er
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    You must have done something wrong yourself if you took out the tension thing. When everything's fitted, it should be held in place by the crank and the pinch bolts, making it very difficult to remove
  • bails87bails87 Posts: 12,998
    My SLX crank came loose and fell off when Evans gave me a road BB with it, rather than an MTB one. The road one is slightly wider, so with the "correct" number of spacers the BB shell and bearings were too wide and the NDS side didn't have enough axle to hold onto. Changed it for a MTB one and it's been fine ever since. So could be wrong BB or too many spacers.

    Yeehaa: Really? I've never tried it, but I thought it would be like the headset cap, once the 'clamp' bolts are tightened it's redundant and you could remove it if you wanted? Unless the compression effect from tightening the bolts means that the plastic preload thing is trapped.
    MTB/CX

    "As I said last time, it won't happen again."
  • GiraffotoGiraffoto Posts: 2,078
    bails87 wrote:
    Yeehaa: Really? I've never tried it, but I thought it would be like the headset cap, once the 'clamp' bolts are tightened it's redundant and you could remove it if you wanted? Unless the compression effect from tightening the bolts means that the plastic preload thing is trapped.

    Yes, once they're torqued down the thing won't shift. But if you set the pre-load and tighten just one bolt so the crank won't shift, it will come out without too much effort. (The bolts don't need to be torqued right down just to hold the pre-load pressure - they need it to stay on when you're pedalling. It only takes a little bit of tightening to keep the pressure up on a stationary bike) Then you can carefully torque both bolts in accordance with the factory settings.
    Specialized Roubaix Elite 2015
    XM-057 rigid 29er
  • nicklousenicklouse Posts: 50,675 Lives Here
    bails87 wrote:
    My SLX crank came loose and fell off when Evans gave me a road BB with it, rather than an MTB one. The road one is slightly wider, so with the "correct" number of spacers the BB shell and bearings were too wide and the NDS side didn't have enough axle to hold onto. Changed it for a MTB one and it's been fine ever since. So could be wrong BB or too many spacers.
    but the design of the shimano set up will actually compensate for that. it should not have fallen off if fitted correctly.

    I run one with that has 2.5mm less than recomended axle in the arm and it is fine.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    bails87 wrote:
    Yeehaa: Really? I've never tried it, but I thought it would be like the headset cap, once the 'clamp' bolts are tightened it's redundant and you could remove it if you wanted? Unless the compression effect from tightening the bolts means that the plastic preload thing is trapped.
    Theoretically, you can remove it, it's job is done, but it's trapped by the crank compression, as you say.
  • The RookieThe Rookie Posts: 27,802
    A correctly torqued bolt doesn't undo, either it's not correctly torqued, or the joint is failing, possibly as the arms are damaged where they go on the axle.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • YeehaaMcgeeYeehaaMcgee Posts: 5,740
    If correctly torqued bolts didn't undo, then nobody would ever suggest periodically checking them.
    Not only that, but your common or garden torque wrench can be wildly innacurate.

    However, I agree that the arms, and possibly the spindle are now more than likely damaged due to not being fitted correctly at one time.
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