Stripped bottom bracket threads -solutions please

[grey-beard]

https://www.sjscycles.co.uk/bottom-brackets/103-first-threadless-68mm-sealed-bearing-bottom-bracket/
I just fitted one of these to a Raleigh frame with trashed BB threads. Rode 30+ miles yesterday and all good so far, no creaking and didn’t come loose. Good quality bearings that can be easily replaced.

That look good too.

 

[bagpuss]

Hmm .
I wore out the bottom bracket threads on my Mercian Vincitore Special following years of hard use .
It really has, had some grief .
Tried the threadless Velo Orange loctited in . I soon managed to unwind it . A lot of torque goes through it from a big sod like me .
Not enough meat on the shell to re thread it .
So is cut and shut an option . Insert a new thread sleeve ?
Or use epxoy resin ?

£400 for a new Special b/b unit . So that's not going to happen .

Thoughts welcome .

 

[grey-beard]

Hmm .
I wore out the bottom bracket threads on my Mercian Vincitore Special following years of hard use .
It really has, had some grief .
Tried the threadless Velo Orange loctited in . I soon managed to unwind it . A lot of torque goes through it from a big sod like me .
Not enough meat on the shell to re thread it .
So is cut and shut an option . Insert a new thread sleeve ?
Or use epxoy resin ?

£400 for a new Special b/b unit . So that's not going to happen .

Thoughts welcome .

What about those that repair bottom brackets above? £20.

 

[bagpuss]

Thanks.
Placed order.
Proof will be in the pudding.
I do like my puddings

 

[Nob]

Thanks.
Placed order.
Proof will be in the pudding.
I do like my puddings

 

[bagpuss]

Trouble is I am far from light.

As for my best before date ,frack knows.

 

[JulianThx]

Depending on how bad it is, and how much you value the frame:

The Loctite Form-a-thread kit (#28654, or PC 3967) is a good basic thread repair system, and should be OK for a large diameter, low load fine thread like a BB shell. You spray a release compound on the male thread (cup), and a cleaner/primer on the female thread (BB shell), then mix and apply the epoxy into the thread and assemble. The release compound allows the cup to still be screwed out as normal.

I also have the 45° cutting tool for putting the appropriate chamfer on the BB faces if you're going down the threadless BB route, such as Mavic YST, or M-wave.

A quick and nasty repair (only for frames that you're not too attached to, probably) is to take a 2-3 mm straight cut across the underside of the BB shell. Close up the shell with a combination of brute force and heating, then weld or braze up the gap, then retap the threade into the fresh metal of the now slightly smaller diameter shell.

As @Peachy! mentioned above, I have repaired several BB shells by reaming out the old thread to a larger diameter, tapping out to Italian spec,

View attachment 598535

then fitting a pair of thread repair helicoils.

View attachment 598534

These are steel inserts that are screwed into the Italian thread, held in with Loctite 638 Retainer, with a standard BSA thread on the inside.
This is the best way to sort it out.

PM for more details if you're interested.

View attachment 598536

All the best,

I would like to try the method of repairing damaged bsa threads with Italian inserts. Where can I find inserts like this?

 

[danson67]

Julian, I don't know of any inserts to give an Italian thread.
If you have a damaged BSA thread and want an Italian thread, then just find a framebuilder with some Italian taps.

The BSA thread repair above relies on the fact that Italian thread is slightly larger diameter than the BSA, so once the Italian thread is cut, the insert steps it back down to a good new BSA thread.

If this is what you require, they are made by Eldi (Art 606), can be bought from Peter at Ceeway (https://www.ceeway.com/Sundry-Components.htm), or I can sell you a set (£15+postage)

All the best,

 

[paton]

Ellis Briggs can put a new bottom bracket shell on an old frame.

 

[paton]

Sunlite and Acor do a bottom bracket for damaged BB shells
https://www.sjscycles.co.uk/bottom-...ttom-bracket-for-frames-with-damaged-threads/
https://www.modernbike.com/sunlite-...-taper-jis-bottom-bracket-for-stripped-frames
Mavic used to do a 610 RD bottom bracket

https://disraeligears.co.uk/site/mavic_-_trade_catalogue_1986-1987_page_27.html