The background - I installed a Miche Primato track crankset with its matching Slovakian-made sealed bearing bottom bracket unit on my Mercian Vincitore c.2005 or so. Maybe c.2010 I thought it was the source of a creaking noise, so I acquired a second unit and swapped it out, realized it was my pedals after all, and swapped back in the original cartridge unit using the original aluminum alloy retention cups. Everything worked well for many years and it was a set-it-and-forget-it deal.

Until late last year, when I realized the drive side had unthreaded itself so much that the left crank was rubbing the BB shell. I limped home and discovered the right/drive side cup threads had failed. I attributed it to age and swapped in the pristine, new cup, set that beautiful buttery smooth cartridge unit back in place and declared it done.

Until today, when 40-odd miles later I discovered the new mounting cup doing the same thing. Ugh.


This system uses two separate mounting cups that are separate from the cartridge bearing/spindle unit. Here is what caught my eye - drive side all the way out, left crank rubbing the BB shell.

I discovered the threads were damaged and no longer held the cup firmly in the BB shell.

Meanwhile, the LEFT side had somehow screwed itself deep into the shell. I didn’t see that coming!

Threads are trashed here - AND on the replacement unit I fitted. Ideas?


So, first question - what causes this to suddenly happen after many years of flawless operation?

Second, bigger question - this BB system is the older symmetrical 109 mm ISO type Miche used prior to 2013, when they switched to JIS taper. With this crank I get a pretty much ideal 42 mm chainline.

If I go to a JIS BB, which pretty much everything is now, will a 103 get me close enough? Or should I just say, “Enough,” and replace the crankset with something else with a more normal BB?