Facebook Twitter LinkedIn Pinterest Bluesky Threads Hello all, I am building a DIY carbon mtb and need help identifying this BB. Any help is greatly appreciated by prich89 Bicycling Bike Bike Repair Biking Cycling Repair
Jumpy-Birthday8446 on December 13, 2025 5:11 pm Perhaps try a rule or callipers and preferably metric, rather than imperial tape measure and you’ll find whatever it is here: [https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.html](https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.html)
biscutgravy on December 13, 2025 6:14 pm Use a metric caliper, but looks like 1.75 in which is roughly 44mm. So much larger than BSA like someone else has mentioned. So maybe T47
4 Comments
does it has threads?
Perhaps try a rule or callipers and preferably metric, rather than imperial tape measure and you’ll find whatever it is here: [https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.html](https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.html)
Use some calipers man good god
Use a metric caliper, but looks like 1.75 in which is roughly 44mm. So much larger than BSA like someone else has mentioned. So maybe T47