Bottom Bracket Help!

Posted on
Page
of 2
/ 2
Next
  • Hi,

    I recently bought a Fuji that had been converted over to single speed. When I first bought it, it had the crank fitted to the left hand side of the frame and was told by my local bike shop that this is a faux-pas and not the best thing for the bike long term.

    This morning I took the crank off and went to switch it over to the other side and the crank now hits the frame and isn’t in line with the rear cog. The bike also has a lot of thread sticking out of the bottom bracket and I don’t really understand how to fix it. I’ve attached some pictures and would really appreciate a hand!

    Sorry if this is a stupid question. It’s my first bike and I really want to learn how to maintain this myself. I’ve been working on cars for pleasure, for the past 8 years, so am confident that I can fix this without going to my local bike shop.

    George


    3 Attachments

    • 67AEFC12-F6AD-4BEF-B8FC-EAA777F0B24C.jpeg
    • BDB7C1C0-E07C-473D-AC0F-039F2168EBC2.jpeg
    • A18EF624-9073-4BC0-977C-43BB9114A185.jpeg
  • take the BB out and put it in the other way around.
    one side will stick out more allowing you to your crank on without interefering

  • That won’t work, drive side cup will be left hand threaded, non drive will be right hand threaded.

    @user118774 looks like you might have a 73mm bottom bracket in a 68mm shell.

    The bit of axle sticking out on the right hand side looks very short.

    You probably want to whip the bottom bracket out and see exactly what you are dealing with.

  • Annoyingly they’re Cross threaded in!

  • Thanks for your help guys. Now not sure how I’m fixing this 😅

  • Take it to a bike shop, say "make it work", give them money.

  • Really? It's difficult to say for sure, but the lip on the end of the drive side (tigh-hand side) bottom bracket cup looks flush to the shell. Also, if they were really skewiff the bottom bracket might not even fit into the non-drive side (left) cup.

    Have you tried removing them both (bearing in mind that the right hand cup will be left-hand threaded and so needs to be turned clockwise to be removed)?

  • @M_V I was a bit silly there, I dont know what I was thinking.

  • Shouldn’t be, that really looks like a driveside cup on the driveside of the bike and a non driveside cup on the non drive side.

    Italian cups wouldn’t even fit in a BSA shell so the threadings can’t be different.

  • Has someone stuck in the wrong bottom bracket and to dig themselves out of the hole put the drive side on the left? If so classy bodge....

  • Sick BMX people do this. Otherwise it's just fucked up.

    The crossed threads thing suggests your frame is a goner.

  • Put in a threadless BB

  • Go hambini... bracing myself

  • How do you even do it though? You presumably have to mount the freewheel reversed, but how can you do that when the notches that receive the tool would be hidden and subsequent pedalling would unwind it off the hub?

  • Take the bottom bracket off because there's something weird happening inside the shell. The whole unit's offset to the left somehow, which is why the chainline is off.

  • Unless you have some sort of custom made hub and sprocket with reverse threads and a reversed freewheel mechanism, you can’t have a left side drive *(the Americans had this in the 2016 Olympics in the team pursuit but they still didn’t win).

    Assuming the threads in the BB shell aren’t fucked, either buy a wider BB or get a spacers and put it between the drive side cup and the shell.

    If the threads aren’t useable then a threadless BB is probably the cheapest option.

    By the way, the lockring is missing on the non-drive side and with it in place, the BB looks more or less correctly fitted. Just that the axle too short to get a proper chainline with that frame and wheel combo.

    • For pedants, it is theoretically possible if you use a sprocket that attaches to the hub using disc mounts on a disc brake wheel.
  • By the way, the lockring is missing on the non-drive side and with it in place, the BB looks more or less correctly fitted. Just that the axle too short to get a proper chainline with that frame and wheel combo.

    If that's a standard modern cartridge BB (which it looks like) then it won't have a lockring, the NDS cup just tightens down against the NDS bearing and sits flush, or slightly sub-flush, with the BB shell. I reckon @M_V might be on the money that it's a 73mm, fitted to a 68mm shell because the axle looks like it protrudes roughly the same distance beyond the cup on both sides.

  • How do you even do it though? You presumably have to mount the freewheel reversed, but how can you do that when the notches that receive the tool would be hidden and subsequent pedalling would unwind it off the hub?

    You get left hand drive freewheels and/or hubs. Ratchet mechanism is reversed, threads are reversed etc. Bmx do it properly, it ain’t a bodge.

  • I reckon @M_V might be on the money that it's a 73mm, fitted to a 68mm shell because the axle looks like it protrudes roughly the same distance beyond the cup on both sides.

    I’d be willing to put money on it being this. It even looks like around 5mm of the nds cup that’s sticking out.

    A 73mm bb in a 68mm shell would sit offset 2.5mm to the nds which would account for the poor chainline and the chainstay clash.

  • A 73mm bb in a 68mm shell would sit offset 2.5mm to the nds

    Would it? Surely the DS side would just look normal since the cup is correctly located, and the NDS side would all stick out by an extra 5mm like we're seeing here.

  • There’s 5mm sticking out the nds because a 73mm shell is wider by 2.5mm on either side.

    With the ds screwed down against the frame the 2.5mm from that side moves over to the nds and adds onto the 2.5mm from there.

  • Ah Yup, I see what you mean. So the spindle of a 73 x 111.5 BB in a 68mm shell will only stick out as far on the DS as the spindle of a 68 x 109 BB in the same shell.

  • Exactly.

  • think you've cracked the case M_V

  • Did you get this sorted @user118774 ?

  • Post a reply
    • Bold
    • Italics
    • Link
    • Image
    • List
    • Quote
    • code
    • Preview
About

Bottom Bracket Help!

Posted by Avatar for user118774 @user118774

Actions