Advice on Shimano Bottom bracket markings

tonyf39 · Sep 29, 2010

Hi, I'm in need of a new BB for a retro racer, I've come across a new old stock Shimano one.
The cups appear to be marked 1,37x24 but also on the box is M35x10 French 68-112
Now I know that the std british threading is the first bit (I think) the 68 is the BB sheel width & the spindle length is 112mm. However what does the M35x10 mean in relation to the fitting. I thought Shimano only produced English & italian threaded cups?

keithglos · Sep 29, 2010

M35 is the old standard French size, RH cup would be RH thread. British RH cup would be LH thread. Perhaps Shimano made some french? and the box contents got switched?

tonyf39 · Sep 29, 2010

keithglos":rbalvhbb said:
M35 is the old standard French size, RH cup would be RH thread. British RH cup would be LH thread. Perhaps Shimano made some french? and the box contents got switched?

Thanks for that, I had some input that it might be the bearing size but the French bit really doesn't add up as old French threaded Bottom brackets went out years ago & the threading is 35x1mm not 35x10 :?

one-eyed_jim · Sep 29, 2010

Some French manufacturers were still routinely using metric threads until circa 1990, perhaps later, and Shimano did make French-threaded bottom brackets for the French market as late as the mid nineties. I own a Shimano UN71 or 72 bottom bracket with French cups.

As to the thread being identified as 35x10 rather than 35x1, I've no explanation, but French thread pitches are often marked in hundredths of a millimetre. I've seen TA bottom brackets marked 35x100. I don't know why that convention exists, and of course your case is slightly different again, but there's no other reasonable interpretation of M35x10 in the context.

Advice on Shimano Bottom bracket markings

tonyf39

Senior Retro Guru

keithglos

Senior Retro Guru

tonyf39

Senior Retro Guru

one-eyed_jim

Old School Grand Master

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