I’m upgrading my commuter and am in possession of 2x SM-BBR60, BC1.37X24 ROAD. Both appear to be identical in every way apart from what I assume to be a factory serial number (SK mn and MC Oz).
I’d ideally like to keep the one that is in better cosmetic condition and sell the other,, so did my due diligence to see male sure it would fit. For whatever reason, the left hand cup did not screw all the way into the frame (finger tightening) whereas the other BB was flush. I’ve counted the threads and measured everything – and unless I’m missing something glaring these are identical?
My only running theory is that the one that doesn’t sit flush came with a spacer, and the previous owner ran that setup leaving some threads exposed to threads need dirt build up and hardening in the threads, making the insertion shallow? Should I put a bit more effort into screwing these in with my BB tool? Naturally I don’t want to strip any threads on the frame, and the sensible solution would be to just have the slightly uglier one of the two and not chance my luck
My question is whether there is anything I’m missing here?
(Well aware the internal cartridge is the wrong way round in picture – attempted fit was without this present)
by jacprc
6 Comments
Apologies for the countless grammar and spelling issues – writing in a hurry between meetings!
I see a ring on one of the BBs, and not the other, could that be the issue? Afaik the plastic sleeve in the middle comes off so you can move the ring on/off as needed.
There is always an amount of manufacturing tolerances concerning any product and threads are no exception. A tiny fraction out can increase the friction generated so you wont be able to screw it all in by hand. In fact it is the more common option that you start a BB off by hand then quickly use your tool of choice, as threads in the frame can also be gunked up and provide friction. There is also the thread lock to contend with on some BB shells as well.
Tightening torque is 35-50Nm which is well beyond finger tight anyway.
check correct sides one has right and one left hand thread
Just at a glance the threads on the right BB look deeper for the one on the right compared to left. Could be the picture. Also the sleeve has lines on different sides. Are you sure they’re the same?
If you have one used and one new and the new one is harder to fit it’s because of the thread locker compound on it. It wears down during installation and that’s why the older fits easier by hand.