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Help! - Crank Removal woes

sjclarksjclark Posts: 64
edited June 2007 in Workshop
As per my previous post on ISIS bottom bracket replacement, I duly went and got all the stuff including a nice new shiny BB (Crank Bros.

However, when attempting to remove the cranks, all that happened was the extractor stripped the threads on the inside of the cranks! Both sides!

Anybody any idea's what I can do now? Angle grinding the cranks off seems a bit extreme but may be the only way.

(Either way, when I am done, I think I will change to a Hollowtech II set up.)

Thanks

Steve

Posts

  • rustychiselrustychisel Posts: 3,444
    Bad news!! Probably an LBS job. A good one will have a crank puller that can hook the drive side spider and pull the crank off, but without knowing exactly what and how it's difficult to comment further.

    I'd like to know how you managed to strip the thread on both cranks: bad interface, massively tightened cranks, operator error, wrong tool for the job?

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  • reminds me when Margaret burnt both her legs getting into scalding bath. always wondered why she never stopped after the first leg...

    You could try putting the bolts back in a bit (so the cranks don't fall off) and go for a spin up the road. The cranks 'may' come loose.

    Mleh Mleh Mleh
  • one of these would take it off without using an angle grinder

    Mleh Mleh Mleh
  • Uncle PhilUncle Phil Posts: 469
    This one can be a bu<i></i>gger.

    If the extractor threads are stripped, you'll need something like the tool Steve suggests. It's known as a flywheel puller or hub puller; you can get them from car tool or parts shops. It'll work OK (probably) on the LH crank, but, particularly if yours is a 5-arm chainset, it's difficult to get a puller to pull evenly - it may tend to slip off to one side as you tighten it.

    Even with one of these, if your cranks have been on a while, or were fitted with no grease on the spindle, they may have corroded on very tightly. Heating them, allowing them to cool and then trying again may help.

    I've had to resort to cutting cranks off with a grinder in this situation (managed to save the axle though).

    Another time, watch the crank extractor carefully. If you see the part that screws into the crank start to move relative the crank - STOP! If you stop at once, you may have left enough thread intact to try again after heating. If you don't, you're knackered.

    Cranks are usually alloy; crank extractors are usually steel. If the crank has been fitted to the spindle dry, and has then corroded on solid, then when the extractor is wound up, something has to give. If the force required to pull the crank off the spindle is greater than the force required for the hard steel extractor to strip the thread in the soft alloy crank, what gives is that soft alloy thread.



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    "Unless someone like you cares a whole awful lot
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  • dakidcpdakidcp Posts: 744
    I stripped part of the threads from one of my cranks because I hadn't tightened the nut of the crank puller in far enough. Very silly thing to do, but was quite lucky and got away with it in the end. Dunno how long it'll last though!

    <hr noshade size="1">"Get a bicycle. You will not regret it, if you live."
    <i>Mark Twain</i>
    <hr noshade size="1">"Get a bicycle. You will not regret it, if you live."
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  • AsterixcpAsterixcp Posts: 6,251
    All you need to know about crank arm removal and installation.

    See page 17 for advice about stripped threads.


    Pour vivre heureux, vivons le v‚lo..
    Pour vivre heureux, vivons le v‚lo..
  • sjclarksjclark Posts: 64
    Assuming that I manage to get the cranks off, if I am switching to HollowTech, how do I tell is I an using English or Italian threads? (Bike is a Halfords Carrera Vanquish - currently has ISIS bottom bracket).
  • MarktaMarkta Posts: 767
    <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by sjclark</i>

    Assuming that I manage to get the cranks off, if I am switching to HollowTech, how do I tell is I an using English or Italian threads? (Bike is a Halfords Carrera Vanquish - currently has ISIS bottom bracket).
    <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">


    Because English threads have a right hand thread ie. the drive side will do up by tightening clockwise, with non-drive side anti clock. Italian threads are exactly the opposite..

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  • [:)] Good advice from Steve Austin. Get some heat into the ends of the cranks with a gaz blowlamp if you can then heave off up the road in the biggest gear you can find. Keep the front brake binding if you feel you are going too far...
    Do make sure the crank retaining bolts are in but not tight [;)]
    The cranks are dead now anyway, and you have a new BB - [}:)] get in there with the angle grinder and make sure it's a metal cutting disc and not a grinding disc - there is a difference [:)].
    Do post your results and how you did it - people with problems seldom do. [:(]
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