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  • Just cross threaded my bb shell!
  • celticdragon
    Full Member

    Does anyone know the thread and size shimano use for their bottom brackets? Standard external XT if it matters. I’ve got an motor factors near work so hopefully they’ll have a tap I can buy if anyone knows the size.

    MoreCashThanDash
    Full Member

    Unless you’re planning on doing it regularly, is it worth getting the tool or just getting the LBS to do it this once?

    Speaking as someone who did the LBS route a year or two back and is now much more careful with BBs

    scc999
    Full Member

    http://www.sheldonbrown.com/cribsheet-bottombrackets.html

    Should be able to find what you want on there.

    Si

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    frogstomp
    Full Member

    I’m not sure a motor factors would have what you need, either in size / pitch and left/righthand thread (depending on which side you’ve done it).

    Your best bet is a good LBS which should have the correct tool.

    TimothyD
    Free Member

    Argos can resleeve your BB shell for you too.

    Dunno about where to find the tools.

    SJS could be worth a look?

    crashtestmonkey
    Free Member

    You’ve cross threaded the full depth of a BB cup, that’s good going.

    If you’ve only cross threaded the first few threads (more likely) then fitting the BB square will recut them and and the BB will engage with the rest of the threads fine. Had an alloy road frame in this state for years with no issues.

    andyl
    Free Member

    what was the frame made of if you cross threaded it with a nice soft aluminium shimano cup?

    mick_r
    Full Member

    A motor factors won’t have those taps.

    You also need the handles to get everything square – like that Cyclus one at Rose bikes linked above. Note that the dies on that one are carbon steel so don’t stay sharp for many frames (especially if cutting steel – I know – I’ve got it).

    Cheapest option is a good bike shop to clean it up for you. If totally buggered then another option can be re-threaded Italian size.

    More expensive but maybe better overall value than the Cyclus is an Icetoolz set including all taps and facing tools for headset and bb. Just £200 at Winstanleys……

    https://www.winstanleysbikes.co.uk/product/69430/IceToolz_BB_TappingHeatube_Reaming_Facing_Combo_Kit_E185

    martymac
    Full Member

    A good bike shop will probably be able to re tap the bb using a correct tool, if you’ve only put it in a couple of threads.
    It happens more often than you might expect, and truthfully isn’t that big a problem.
    If you’ve managed to get it all the way in, then I’d say you must be (genuinely) really strong, that won’t be easy.

    Onzadog
    Free Member

    I’ve recovered a few for other people in the past in alu frames by using an old steel bottom bracket.

    fourbanger
    Free Member

    I got my LBS to tap the BB after I has it powder coated. They managed to cross thread the tap…
    Their advice, bridge the BB in and leave it out.
    My advice, buy the tool.

    onandon
    Free Member

    Same as onzadog- I keep a old steel shelled square taper bb for cleaning up threads.
    It won’t help you now but worth having one in the parts draw.

    bencooper
    Free Member

    First bike I built for myself, when I was barely a teenager, I managed to fit the bottom bracket backwards. I thought it was a bit stiff going in 😀

    A motor factors won’t have it, it’s a pretty specialist pair of taps – but any bike shop worth their salt will have the tool and be able to do it for you. Unlikely you’ve borked the frame.

    dovebiker
    Full Member

    ISO/BSC thread is 1.37″x24tpi. If one side is OK, it should be possible to chase the thread from one side, carefully followed by the other. If you’ve not tapped-out a BB thread before worth finding someone who knows what they’re doing..been in a few LBS workshops and you don’t want to go somewhere where they’ve let the Saturday lads loose on the tools….

    Klunk
    Free Member

    always very paranoid when putting in external bb cups so always goes in “greasy” finger tight only and any resistance it’s out and try again the proper tool is only used once it’s all the way in to tighten up.

    5plusn8
    Free Member

    My next door neighbour has this one. https://www.rosebikes.co.uk/article/cyclus-thread-cutting-tool-for-crankset-casing/aid:22920?
    Even my hamfistedness was able to rescue my steel racer and a newish alu frame with this tool. If my neighbour didn’t already have it I would buy it.
    Just make sure you get them the right way round. They are labelled L and R, which as it turns out is the thread direction not the side of the bike, from memory its and LH thread on RHS of bike and vice versa. I just compared them to the new BB cups to prevent stupidity.

    PeterPoddy
    Free Member

    I’ve got a home workshop that would embarrass more than one bike shop I know of, I’ve got some pretty serious tools. The one thing I do t think I’ll ever buy is BB taps. They just don’t get used enough and are very expensive for a single use.
    That said I’m lucky to have my own set at work, but even here they don’t get used that often. Once a month maybe? Our price is £30 for a BB fit including facing the shell and chasing the threads. And I know how it’s done, and I won’t bugger your frame up. 🙂
    Go to your LBS.

    5plusn8
    Free Member

    Yeah I can see your point, I think would counter it by saying:
    1) At 75 for the cylus tool it is 2 of your bb chases?
    2) Keep it in greased paper and it pays for itself in the end.
    3) Neighbour has done 4 bikes and I’ve done two, plus he lent it to other people.
    4) I paid him in wine.
    5) You tube tells you how to chase threads.
    6) Some of the evidence up there shows even LBS have no idea how it is done.
    7) Satisfaction of a job well done.

    Mr Poddy drop me an email and I’ll get the neighbour to lend it to you next time for postage. (Unless you are near Gatwick)

    PeterPoddy
    Free Member

    5) You tube tells you how to chase threads.

    Go on then sunshine, you crack on with yer cheapo tool.
    £30/ was face, chase and fit. Does that cheap tool face the shell?

    6) Some of the evidence up there shows even LBS have no idea how it is done

    And lots more to suggest that ameteur bodgers screw up their own work.

    Don’t let me stop you….. 🙂

    finbar
    Free Member

    On a similar note to PP, literally the only bike job I’ve paid a mechanic to do for me in the past five years was to chase the BB threads in a Chinarello that came fresh off the boat with resin in the threads. They charged £15 (no BB fitting) and did a fine job.

    5plusn8
    Free Member

    And lots more to suggest that ameteur bodgers screw up their own work.

    Well I base my anecdotal evidence on myself, who is a bodger, who managed to do it twice without mucking it up. I’m not a bike mechanic though so I defer to your experience. You can still borrow it though, neighbour seems keen to prove its value. I guess that’s the opposite of buyers remorse?

    CalamityJames
    Free Member

    Speaking from experience, a good LBS will fix for you and treat it as a one-off lesson – you won’t make the mistake again.

    monkeyfiend
    Free Member

    Many years ago a friend had his work powder coat a frame for me, it wasn’t masked off very well and so I had to pick out the threads using various home made sharp edges, it took forever (not literally though).

    so… when I had an Alu frame that was dropped and slightly squashed the first 2 threads of the BB shell, I checked out the LBS instead, and they chased the threads out for £10 while I waited on a very busy 1st day of opening after Xmas.

    (Big thumbs up to Leisure Lakes Cheltenham)

    At that price I’m never going to buy a specific tool for it.

    celticdragon
    Full Member

    Thank you all, I managed to mangle the first 4 mm of the BB cup, which got rescued by inserting it into my steel On One frame. I’ve also mangled about 6mm of thread in the BB shell, about 1/2 way in so thats going to be a tap only job. When I make a mistake, I do it properly!

    I’ve got my spare Shimano BB in there now so it can wait until I give it a strip down before my holiday in August, as it turns out my BB spanner doesn’t fit the MT8000 XT BB cups so need an adapter / new tool for that. Oddly enough it fits my current Shimano (Deore), Token and with adapter Dura Ace BB’s.

    As for cost, with 3 bikes, 2 of which could / need threads cleaning, buying a tool to do it, is only about 2x the cost of the LBS, and I’ve got it should I fluf it up again.

    Living on a sandstone ridge, means bearings and drive train don’t last long between services / replacement.

    Northwind
    Full Member

    monkeyfiend – Member

    Many years ago a friend had his work powder coat a frame for me, it wasn’t masked off very well and so I had to pick out the threads using various home made sharp edges, it took forever (not literally though).

    Pro tip- get an old BB and cut full thicnkess slots across the thread. It’ll not cut a new thread or do much to fix a damaged one, but it’ll clear paint, plastic, threadlock, fossilised mud or anything else softer than aluminium out of the thread.

    (re facing- if the metal is straight you can clear off paint with a razor or something like 400 grit. If the metal’s not straight, you have bought a horribly built frame and chances are something else will be wrong too.)

    daver27
    Free Member

    new XT m8000 bbs do require an adapter tool, its a plastic thing thats easily mangled to give you a heads up. They come with the new BBs but are like hens teeth to find as spares on their own

    celticdragon
    Full Member

    My BB didn’t come with one, just came in a white plastic bag, sent from a well known supplier.

    IHN
    Full Member

    Big thumbs up to Leisure Lakes Cheltenham

    and there’s a phrase you won’t hear often

    gummikuh
    Full Member

    I needed one of those adaptors for XT BB, and mine also came in a plastic bag from a well known supplier. My Local bike shop had a root around and gave it to me for free, I was so impressed I had to go across the road and buy a couple of packets of hob-nobs for them.

    takisawa2
    Full Member

    See if you can get a quarter segment of an old steel bottom bracket cup…
    If you can drop it in to the thread behind the cross threaded bit you might be able to clean it up by chasing the thread outwards…if that makes any sense…
    Its tricky but might just open the damaged thread up for you.

    I had an Italian threaded BB reamed & sleeved once.
    Its a straightforward job. (If you have the kit etc).

Viewing 32 posts - 1 through 32 (of 32 total)

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