i have a steel road frame with really flat threads in the bottom bracket shell. there are cut lines which indicate it there had previously been a seized bb, and i guess it took some shell material with it. it's english threaded and a cinelli shell. a chaser goes in fine, but a cup rattles around.

i just tried filling the shell with jb weld and re-tapping to english - no go, all the jb weld chipped out.

now i'm looking for other options. i want to save reaming and tapping to italian as a last resort.

i'm thinking of trying loctite form-a-thread,
https://www.cheapbikeparts360.com/pro...ad-repair-kit/
but i don't want to waste my time with more glues if it won't work. any advice?

A threadless bottom bracket could be the solution to your problems

In years past, Mavic made a square taper BB that was designed for just this situation. It has tapered lock rings that fit to the external edges of the BB shell (tapered edges, shell needs to be prepped for it, to seat the lock rings properly). Just a thought for additional options.

Velo-orange makes a similar modern product that is available.

Once you bevel the shell for the threadless bottombrackets, there is no going back. I'd either braze-fill the damaged threads on the existing shell and recut the English threads (and repaint) or, better, ream and rethread to Italian. If you eventually ruin the Italian threads then a threadless bb would be a last resort.

The Velo Orange Bottom bracket that Operator and I posted does not require that you bevel the bottom bracket shell. If you decide at some point later that you want to try to re-tap the threads, there's no problem.

Brazing some fill and retapping would not be an inexpensive solution. It's definetly a machine shop job just to add the filler and then bore it on axis in prep for the threading. And cutting big, fine pitch threads is not something that is easily done by hand so again you're likely looking at another shop bill. All told it had better be a pretty deluxe frame to justify the price.

I'm currently in the same boat with an older Cannondale touring frame. I'm either just going to retire it or buy the Velo Orange BB. The only other thought is to fire up my shop machines and produce a press in threaded sleeve and then to set up the frame in my mill and bore out the BB shell to take the press in sleeve. And that is only practical thanks to the generous wall thickness used in the early Cannondales. More likely I'll just do the Velo Orange BB thing since it would be FAR less trouble and cost.

I lookat at that Loctite thread repair stuff. Reports of using it here on BF and other places did not make it sound worthwhile for THIS application. LIkely it's something to do with the fine threads and large diameter but it didn't work out well at all.

The other thought is that if the BB threads in OK and you can torque it to the minimum of the desired range of torque then do that and call it good. Threads like BB's seldom are a precise fit and it's not at all uncommon to have some play in the threading. Just grease it up before you do this. And if it strips out when you are trying to torque it to the spec then just consider it as a preporatory reaming operation to better take the VO BB....

threadless bb is of course a good option, but i want to use an ultra-torque crankset. i could ditch the cranks but i'd need a bb with an ISO taper to run my campy group. the mavic bb is ISO, but it doesn't seem to come in a short enough axle length for campagnolo cranks.

i'm starting to feel like tapping to italian may be my only viable option. does anyone have any actual experience doing this?

Aha, I just looked at the Velo-orange web site and I was wrong, they do not require beveling the bb shell. So, they are a good fix for stripped English, French or Swiss threads but only in JIS taper. If the cartridges themselves are reliable, it sounds like a good repair.

O

The braze fill is cheap if you already own the torch and tanks. and re thread is not too bad ,
a buddy did this on his basic transport bike... He is a boilermaker - welder.

Only the Mavic bottom bracket requires bevelling. The Velo Orange bottom bracket does not require this, nor do other threadless bottom bracket cartridges, e.g. EDCO.

Bicycle Research used to offer a reamer/tap set that would ream an English/French shell enough to allow it to be re-tapped as Italian.

You may find this interesting

https://tsaleh.blogspot.com/2010/01/r...hreadless.html

It would appear that to get a nice seating that the old threading pretty much HAS to be missing or it won't seat in all the way. In addition it would appear that for some BB shells that a drum sander to ease the stripped threading a little to allow proper seating of the flanges may be called for. A bit of a pain but it's still an option that will keep an old frame on the road instead of resulting in scrapping it for ruined threads.

It would appear that you read a completely different article.

IIRC, Campy cranks come with the bearings on the crank arms and the frame simply gets "cups" installed. Given that set up, you could always epoxy the cups into the frame and so long as you stick with the Campy crank, you'll never need to bother removing the cups. Loctite makes numerous products that should do the trick especially when aided by the existing threads. Not an ideal fix but it's far easier than reaming and retapping to Italian threads.