Loose bottom bracket

Hey guys,

Riding to work this morning along the Yarra, I passed Chrisof (hi!), and then noticed my bottom bracket was virtually falling off the bike. Now as many of you might know, my mechanical skills are not the greatest so I thought I’d ask here first.

Basically I first noticed the problem when my pedal strokes didn’t feel completely circular ( :-o). Looking down at the bottom bracket I noticed the right side was about to fall off. Now the right side is the fixed side isn’t it? So what’s going on?
I managed to thread it back on my hand enough to continue to work, although I can imagine riding the bike in this condition is not a great idea.
Is this something I can fix myself? It’s a shimano sealed-bearing BB with a steel right side, with a cream plastic cup left side.


It has worked loose.

You’ll need a couple of tools, but you can manage ok…

1: Remove the cranks.
2: Remove the BB and plastic cup.
3: Clean the threads and BB shell.
3a: If the BB is Italian threaded, spread some loctite on the threads.
4: Install and tighten the ‘fixed’ steel side as much as possible.
5: Install the plastic side cup and tighten.
6: Tighten the fixed side some more, and then plastic one.
7: Replace cranks.

There is probably a “more correct” way to do it - but that should get you going :slight_smile:

Thanks nath,

Seems like a simple fix. How does such a thing come loose though- is this unusual or can it work itself out over time? It’s a bit disconcerting when these things happen… :evil:

Because it wasnt tight enough to start with.

I’d just take out the BB, clean and grease the threads and tighten the fucker!

Dont forget to put your shirt back on.

Hi :smiley:

I have some tools if you need, can bring them tonight. Let me know.

You wouldn’t believe how cold it gets riding without a shirt in the winter mornings… :evil:

Now I have a mental picture of you riding shirtless, but with arm warmers and winter gloves to keep the cold at bay.

PS, if anyone’s using the Campy AC-S/AC-H BB and needs the tool, I have the Park version available for borrowing.

Ah, it is Italian threaded. Are Italian threads unusually loose or something? What’s the reason you mention this?

I did as you said (minus Loctite) and it seems fine so far. The problem is my SuperB shimano tool is not the best quality so it’s hard to get massive amounts of torque when tightening.

Italian threaded Bottom Brackets do come undone without locktite, because the treads dont oppose the direction of the spinning cranks.

You will need locktite to prevent it coming undone in the future. My road bike has an italian threaded BB and there was so much loctite on the BB cups from new that the BB shell on the frame heated up when i fitted them.

Loctite is pretty cheap and very versatile and you can get it from almost any hardware store.

I don’t quite follow. Can you elaborate?

Kind of like a suicide hub?

My interpretation:

The direction that the crank turns is also the direction to loosen the cups.

The drive side is right hand threaded. English threaded BBs are left hand threaded on the drive side. (therefore, pedalling forward is the same direction to loosen the drive side cup)

However, I’ve had Italian BBs that have never loosened.

I think Horatio’s BB just wasn’t tightened enough when it was installed.