TheChief

I am having a new frame built, my old Trek 710 is just too tall for after some 37 years, and I need some help understanding the bottom bracket specs. There was no problem with my old Campy NR bottom brackets I just used the English bottom bracket for the Trek and the Italian for the Zullo (which was way too tall when I bought it!) I am looking at these new cartridge bottom brackets and I keep seeing BBS15 on some and BBS18 on others. What is a BBS15/BBS18 and what is the difference between the two? Thank you in advance for your kind courtesies in helping me with this.

AeroGut

If you’re looking at the Sunrace products, the main difference between BBS15 and BBS18 models is the use of aluminum (15) vs steel (18). The various specs are in this pdf: https://www.sunrace.com/files/catalog...20Brackets.pdf

once you decide which one you want, you then need to know what spindle length.

TheChief

Thank you, I checked out the information on the link you provided and I see that the BBS15 and 18 are model numbers identifying material and sleeve design. Interesting that I never realized that before.

dedhed

I'd be looking at Shimano or Tange, maybe even SKF or Phil Wood if was having a custom frame built.