Removing a stuck Bottom Bracket shell

[Martin]

Following on from the shopping bike thread; a method that hopefully may be of use with no welding no special tools no vice, bench or assistant 

this method assumes you wish to remove and replace the whole BB with a sealed unit

If the RH side shell is of the type below, or even thinner as mine was. First remember it's almost certain to have a reverse thread so needs to come off clockwise




It's pretty much impossible to get enough purchase on those flats with any tool or vice.

Having first removed all the other bits (and liberally sprayed with WD40 / GT85 preferably a few hours before) get a big nut and bolt at least 17mm head with a spacer if required (almost as big as the axle hole) push the bolt with spacer through from the inside. Place a ring spanner between the shell and the nut. Tighten the nut with a second (preferably ring) spanner until both spanners are at 180 degrees to each other and the nut is fully tight.

HEAVE!! it should work

in pictures

The bolt placed through the shell with a socket spacer inside and the first spanner installed



the second spanner which is going to tighten the whole ensemble up and make it work



(not tested) how to use it on a non reverse thread; for this purpose you will need to replace the spanner with a socket unless you have a long bolt and spacer. For realy obstinate ones you can add two locknuts and a second spanner on the outside thread

[Feanor]

Trying to visualise this...

What's the purpose of the first spanner, between the shell and the nut?

[Martin]

Trying to visualise this...

What's the purpose of the first spanner, between the shell and the nut?

in my case it was a spacer to allow the outer 17mm nut to be clear of the shell and not foul the axle hole. However it also acted as extra leverage so that the 2 spanners formed a T-bar, because as the outer spanner tightened it locked the inner spanner against the shell.

I'll post some photos tonight

[rogerzilla]

A fixed cup spanner (yes! you can still buy them) and a rubber mallet have never failed me, even on rusty frames with a 40-year old BB in them.

[Andy64]

Get a bit of steel welded onto it to act as a big lever. Make sure it'll clear the chainstay though

[Brucey]

assuming that you have an 8.8 grade M14 bolt (and not the weedy M12 ones in the photos which are only a bit more than half as strong) the recommended torque value is ~140Nm (about 100ftlbs in old money). You can go a fair bit more than this before the bolt will actually start to fail, but you might have made yourself a whole new problem in the process.

The point I'm trying to make is that the bolt method is for folk who don't have anything like the right tools, not for folk with properly seized BB cups.   I have had to put over 400 ft lbs onto a BB cup to shift it before now, and well over 150ftlbs isn't at all unusual.

cheers

[Martin]

I Agree, the bb is 3 years old and just done up to factory torque.

So how do you get 400fllb onto really stuck bb?
Not that I'm likely to need it as all my stable now have Shimano sealed units but information like this is really useful to have online a google search led me to you guessed it the LFGSS forum!

[Brucey]

with a (shimano type)  splined tool it can be bolted to the cup and then a suitable spanner/socket can be used.  I have used a 36mm socket on a  3/4" drive breaker bar with an extension on it, making a total length of about 5'.  The problem then becomes holding the frame; to get enough leverage here, lengths of tubing are used (with care) in the head and seat frame tubes.  To my surprise the splined tool (a shimano one, of a kind I have seen break in other people's hands) has survived this treatment several times now. Thinking about it the peak torque used to date  would have been far in excess of 400ftlbs.  Part of the trick of it is to use a flex-headed breaker bar; this allows the handle to be brought back into the same plane as the frame, so that there isn't a secondary couple that you need to fight against, and your effort is not wasted.

If a length of bar is welded to a steel cup, this can be extended using a cheater bar of some kind, or just slogged.  The heat from welding usually breaks the bonds of corrosion to some extent; slogging is highly effective but gives rise to uncontrolled forces. Usually the welds to the cup break before the frame does but there is no guarantee of that.

Seized aluminium cups often require a destructive approach. Once the bearings are removed (by hook or by crook) an aluminium cup can be slotted (sawn) and broken up. If this is done with care, there will be minimal damage to the BB threads.

BTW I forgot to mention; one trick that is widely used in bike shops to remove seized BBs is to 'massage' the BB shell using a hammer. The best method is to use two hammers; one with a large, heavy head is set against the shell on one side as a bolster. The BB shell is the struck using the other, smaller/lighter hammer on the other side, i.e. 180 degrees round from the first position.  If this is done in several places a seized BB cup usually comes free. It damages the paint of course, and even the frame sometimes, but it can result in a time-efficient (and therefore economic) repair that might otherwise not be possible.

cheers

[Martin]

Thanks;

A less onerous task on the same bike was to get the old single speed freewheel off the rear wheel. I took it to Halfords thinking it would be a 2 minute free job but they wanted £25 as it counted as a wheel rebuild. I bought a new one for £3 on ebay which turned out to be complete junk made in India, so had to destructively remove it by prising off the bearing outer and fitted a better one from Decathlon.

Interestingly when I went to Halfords and asked for the BB they were busy so directed me to a drawer under the display shelves full of them, not priced. I picked up one that I'd seen on ebay for £9.99 expecting it to cost double in store but it was the same price, so presumably they sell things like this at wholesale?