bottom bracket threads wrecked on alloy frame!!!

[Dead Rats]

HELP!

Ok not a retro bike, but on upon removing the Truvativ GXP external bearing BB from my '03 Enduro it is clear that the driveside BB threads in the shell are shot. After a short cry, I trawled the 'net for solutions before I ask for your help...

On my very tight budget, here's one possibility - which would obviously require me to buy a matching sq. taper crankset - has anyone tried this (see pic below)? I've read they don't last too long but are LOADS cheaper than the other possible methods!

My other option appears to be sourcing and fitting a English to Italian thread sleeve...

Any advice greatly appreciated!!!

 

[Dead Rats]

I've now read that the threadless BBs are bobbins - with possible exception of Stronglight - and some seem to require 45 degree chamfer being added to BB shell.

Other suggestions are PTFE tape (sounds bodgy - would it really work?), Araldite (or similar) the BB in (once the BB goes, so does the frame), extra-long RH cup (as it's 'only' the first 6mm of thread that is damaged), press fit replacement cups etc.

If you all think these are utter bodges, then can anyone recommend a reliable company that can ream out my frame, fit a sleeve and rethread it? BETD have been suggested?

Cheers in advance!

 

[Splatter Paint]

How about using one of the low-temperature alloy welding kits, i.e. Techno Weld or similar to fill the damaged area. Then file the surplus metal back and take it to the bike shop to get the threads tapped. This will be time consuming and it might be difficult to get enough heat into the bottom bracket for the weld to take.

Argos cycles might be able to help if you want to sleeve it

http://www.argoscycles.com

 

[Dead Rats]

I'm only going to ask the following as I'm on such a tight budget:

As the BB cups have a 2mm spacer on each side (between themselves and the frame's BB shell) could I - theoretically and with some knowledge of the detrimental effect this will have on my chainline - remove the 2mm spacer from the driveside fitting procedure to allow RH cup to bite into an extra 2mm of remaining thread?

Just a thought like... must be worth a try if the frame is already damaged, and if I at least get remaining threads chased, I will still have some thread contact!?

*awaits barrage of disapproval*

 

[scant]

the mavic BB was pretty good. getting harder to find tho.

 

[slimjoe]

Stronglight/mavic brackets

I was in a similar position not very long ago.

Frame builders options and advice to me was:

1) Threadlock your existing bracket into the frame

2) Have the frame bracket shell cut & rewelded up to close the gap slightly, then have threads cut back in.

3) New bottom bracket shell welded in (not so simple on alloy frame!)

4) Use a decent threadless bottom bracket like the Mavic (as suggested) or the Stronglight.

Ive sourced out a Stronglight bracket and my LBS is doing the 45 degree chamfer for me. This seemed like a good solution and i wont lose any paint. Also these 2 brackets are designed to work properly and not just to bodge a fecked frame

 

[Wold Ranger]

BB

Race face ISIS drive BB's have really long threaded cups, Many frames aren't threaded far enough in to take them. If there is some thread left further in, this may work?

 

[cannondale king]

if your bottom bracket shell is alloy and meaty you can have it helicoil its not mega expencive and will be a perfect job after its done and proberly out live the rest of the frame all the other methods seem a little to much like hard work and comprimise but good ideas though and before anyone jumps in to say they done do them that big helicoil's go up to silly huge i know as i used to have to helicoil a lot of parts when i work on seakings in the navy as the touque used to keep stuff inplace was 9/10 to much for some alloys parts :roll:

 

[stew-b]

i doubt very much you would get a helicoil in that size and with a left hand thread :!: :shock: :?:

 

[sancho]

You might be able to re-thread the bb to take Italian bottom brackets. I think they have a slightly larger diameter.