HELP! Pressfit BB knackered, but can't get the crank off (seized content)….

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  • HELP! Pressfit BB knackered, but can't get the crank off (seized content)….
  • robhughes
    Member

    Block of wood and a lump hammer.Don’t go too mad at it and it will go.
    WD40 (both sides)a couple of times first and leave for good 10 mins.
    It,s only plastic so it’s not really bonded.

    stumpy01
    Member

    Typical, and probably a case of lack of maintenance but I have barely ridden the full sus over the winter…I have noticed the BB getting a little graunchy and have been meaning to get it replaced.

    Anyway. I cleaned the bike this afternoon as I am off to CyB at the weekend for a good friend’s stag-do.
    I noticed that there is a small amount of play in the crank, and it looks like the bearings are completely borked.

    I tried to remove the crank to investigate further, but the crank will not come off. It is an XT HTII crank. I have removed the non-drive side crank arm & it looks like the plastic BB part that the crank passes through on the non-drive side has seized onto the crank axle.

    So far I have tried:
    pushing the axle from the non-drive side,
    pulling the crank from the drive side,
    whacking the end of the axle from the non-drive side with a rubber mallet,
    laying the bike down with some raised blocks beneath the end of the axle and pushing the frame down using a decent amount of bodyweight.

    It is getting to the point where I am scared I will damage the frame if I use any more force than I currently am.

    I will probably call my LBS tomorrow & see if I can get the bike into them, but I won’t be able to do this until Tuesday morning. Then, they might be too busy to try to sort it out & even if they have the time they might not be able to get hold of the particular BB that is needed (BB91-42A)….

    Balls. Balls Balls. Should have cleaned the bike last weekend when I wanted to, rather than arse around with gardening & stuff. Ball Balls Balls……

    Any ideas greatly appreciated.

    plecostomus
    Member

    As above hit it harder!

    stumpy01
    Member

    Got it out in the end….

    I was hitting it bloody hard; was starting to worry that I was going to do the frame some damage. I gave it a spray with Plusgas and that did the trick.
    Only thing is I think that the worn BB has knackered the crank. There’s now a groove cut into the crank axle. Don’t really understand how this has happened as the axle runs on the plastic cup.

    So, now need to work out what BB I need. It’s BB91-42A. There’s loads of BB91’s out there, like this one:
    http://www.chainreactioncycles.com/Models.aspx?ModelID=44225, and
    http://www.wiggle.co.uk/shimano-mtb-press-fit-41mm-bottom-bracket-inner-cover/
    but I don’t know if these come with the bits that make it different to a BB91-41A or BB91-41B.

    The tech doc doesn’t give too much away..

    http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/BB/EV-SM-BB91-2987A_v1_m56577569830726016.pdf

    also need to buy a new crank now. Suppose I should get a 2×10…..been thinking about it for a while, anyway.

    robhughes
    Member

    What bike is it off?

    stumpy01
    Member

    Robhughes – It’s a 2010 Stumpjumper FSR carbon.

    Thing is, I bought the alloy version and it went back under warranty due to a pain defect. They gave me the option of the carbon frame as a replacement (or wait for a couple of months for the 2011 alloy frame to come into stock).
    The one thing putting me off was the press-fit BB, but I went for it. Am wishing I’d waited for the 2011 alloy frame now!

    Any help would be much appreciated…..!

    Premier Icon p7rich
    Subscriber

    Same thing happened to me – same bb and same crank. The fit on the drive side is very tight. My drive side cup came out with the axle though…but took me ages to drift/hack half the bb off the axle. No scoring on the axle though. Good luck getting it sorted.

    pitchpro2011
    Member

    Sure your not turning it the wrong way?

    stumpy01
    Member

    Robhughes, yeah I found the Tweekscycles one, but 10 day delivery! I need the bike for a weekend in Wales…
    I thought I mentioned that in my original post, but must have forgotten.

    Yeah, the Spesh question was me!

    Still doesn’t tell me though if the ones on Wiggle and CrC which are described only as bb91 come with the bits in the box to make it a 42a or not…
    It looks like intrinsically the bottom bracket is the same, just the spacers that go into it that are different.

    p7rich, goof to hear it’s not just me. I think when I have replaced it, I will be regularly removing the crank and refitting it. Bloody annoying as the cranks were in good nick.

    Did you take the BB out & replace it yourself? Is it fairly easy without special tools?

    robhughes
    Member

    Nar.Tweeks will have it with you in two days.Iv,e had loads of stuff off them.Always arrives on time.If you look all items say that.

    Premier Icon tthew
    Subscriber

    I bought one from Tweeks last week. The A designation ones are the MTB version, the B version are for road bikes, it came well less than the quoted 7 – 10 days.

    For info, I only changed the one, non-drive side bearing that was knackered. I’d strongly suspect that the only difference between the MTB and road versions is the width of the spacer tube in the middle and lack of 2.5mm shim. So, whatever you can get from your LBS should suffice, (I got the XT 71, but the original was the XTR 91 and the only difference was the colour of the plastic as far as I could see)

    Edit – I had already bought the Park press cups and removal tool in anticipation, whamming bearing in with a rubber mallet is the quickest way to damage the races.

    robhughes
    Member

    There you go….sorted…

    Premier Icon p7rich
    Subscriber

    Did you take the BB out & replace it yourself? Is it fairly easy without special tools?

    Yep, dead easy on a Whippet frame. I think it may have gone in by hand…but i do have one of those cheap homemade screw-rod press tools i use sometimes.

    dantsw13
    Member

    Are the cranks really FUBAR’ed? If the scoring isn’t mechanically damaging will it matter?

    Must say PFBB would put me off too. Too much investment in my Hope bb!!

    Premier Icon billyboy
    Subscriber

    Plusgas the hell out of it……..leave it……hit it. If it don’t move…Plusgas…leave…hit….etc

    stumpy01
    Member

    Well, I have had a bit of a result. My LBS has got one in stock and are gonna fit it on Wed! Terry Wright Cycles in Deeping.

    Dantsw13, not sure if the cranks are fubared or not…need to have a proper look, but there is a large groove all the way round the axle. I could smooth it down & see what it looks like. Need to work out where the groove sits in relation to the BB & whether that is liable to damage the BB more quickly. Also don’t really want the axle to snap mid-ride.

    eyerideit
    Member

    Buy one of these for next time you need to gently persuade a part out without damaging anything and leaving a hand free to hold you brew with.

    stumpy01
    Member

    Yep, was using a rubber mallet to try & get the crank out…

    from my OP:

    stumpy01 – Member

    …whacking the end of the axle from the non-drive side with a rubber mallet,

    It took more than gentle persuasion.
    Never had an issue with HTII cranks or HTII BB for that matter before.

    I am wondering whether some oil/grease I have used is incompatible with the plastic component of the press-fit BB that the crank axle slides through.
    I used to do a lot of material compatibility work at a previous job & plastics/rubbers were very susceptible to chemicals; even if only very subtly so. And it wouldn’t have taken much in this case to cause the ‘seizing’ of components experienced.

Viewing 20 posts - 1 through 20 (of 20 total)

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