Shimano Ultegra Cranks & BB30a

Tdaytona
Tdaytona Posts: 66
edited May 2016 in Workshop
Hi,

My left crank came loose on a ride this morning. There was no warning and the last 3-4mm of the splines a completely ripped. I was wondering if the wider BB could be the problem. Trying to refit when i got home confirms splines are wrecked. The frame is a Cannondale Synapse hi mod, with standard Shimano Ultegra Chainset. I have Rotor BB/Shimano adapter BB, Chain reaction confirmed this was the correct BB for this frame. The bike is a recent build, and only done about 350 miles

I know the Cannondale bike has Cannondale's own crank designed for this BB. 

Anyone else have similar issues?

Thanks

Cheers Paul

Comments

  • edindevon
    edindevon Posts: 325
    Did you service the cranks in line with Shimano document on their Hollowtech II Cranksets? It states:

    The two left crank arm mounting bolts should be tightened alternately in stages rather than each bolt being fully tightened all at once. Use a torque wrench to check that the final tightening torques are within the range of 12 - 14 N·m. Furthermore, after riding approximately 100 km (60 miles), use a torque wrench to re-check the tightening torques. It is also important to periodically check the tightening torques. If the tightening torques are too weak or if the mounting bolts are not tightened alternately in stages, the left crank arm may come off and the bicycle may fall over, and serious injury may occur as a result.

    I know a lot of people rubbish this advice, but it seems to be relevant.
  • Tdaytona
    Tdaytona Posts: 66
    Hi,

    The bike was built by my lbs. Will need to wait till tomorrow to speak to them and Saturday till I can get the bike in. I bought all the bits, so if the cranks/BB are not compatible I am looking around at a big bill. I am concerned that the main shaft on the Shimano crank may be too short. It does/didn't appear to come through the lh crank very far.

    Cheers Paul
  • dj58
    dj58 Posts: 2,217
    You suggest that there is not sufficient axle length protruding through the BB shell/BB/Adaptor combination and therefore the L.H. crankarm was not fully supported, even if correctly torqued.

    I would say that this is down to the shop that built the bike up for you, as even if you specified and supplied the parts and they turn out to be incompatible, they should have informed you and not attempted to fit them.

    There is a post on here about BB30A and problems with getting adaptors to fit Shimano HT II cranksets to the Synapse.
    viewtopic.php?f=40004&t=12973328

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