White Industries external BSA style bottom brackets are made here in our shop with U.S. sourced 6061-T6 aluminum and feature Enduro stainless steel anglular contact bearings or Enduro XD-15 ceramic radial bearings where available. We offer them with three different bearing sizes to help you fit your favorite crank to your favorite bike. "BSA" bottom bracket shells and cups are named after the Birmingham Small Arms Company which created the thread standard used in this system. It's also referred to as "British" or "English" style and is the most common type of system found on modern bicycles. The "external" designation refers to the fact that the bearings will sit outboard of your frame's bottom bracket shell as opposed to being tucked inside the shell as you would find on some styles of BSA bottom brackets. Features Comes in three bearing sizes to fit: - 30mm White Industries M/A/R/G cranks as well as other brands of 30mm spindle cranks - 29mm SRAM DUB cranks - 24mm Shimano HollowTech II cranks Dust seals included with all models - Seals should sit directly against the bearings, with the part numbers (molded into the seal) facing out Internal BB sleeves are not available for our BSA bottom brackets Specs - 1.37" x 24 TPI threads ("BSA" threads) - Designed to be used on 68mm or 73mm wide bottom bracket shells - Weight/pr (with bearings and seals): 30mm: 83g, 29mm: 90g, 24mm: 84g Cup Dimensions, Spacers and Bearing Info - No spacers needed with R30 and G30 cranks on 68mm shells (73mm shells are too wide) - No spacers needed with M30 and A30 cranks on 73mm shells - On 68mm shells, use one 2.5mm BSA cup spacer on each side See the Compatibility chart for the "OBW" (Outer Bearing Width) of each bottom bracket and compare that to the allowed OBW for your crank (ask the crank manufacturer for this, not us!). Most cranks these days have an adjustable bearing preload collar on them that can accommodate slightly wider/narrower OBW's than their target number, but again, you'll need to check with your particular crank's manufacturer. When in doubt, start with few spacers than you think you need so you don't crush and destroy your bearings! - If the allowed OBW of your crank is less than the OBW of our bottom bracket, our bottom bracket will not work (it's too wide for the crank) - If the allowed OBW of your crank is more than the OBW of our bottom bracket, our bottom bracket will work but you may need spacers How many spacers? Other brands of 30mm cranks: - Compare the allowed OBW of the crank to our bottom bracket OBW How many spacers? 29mm SRAM DUB cranks: - Using SRAM's charts, look at the BSA row, find your shell width, find your crank model, then see what spacers they require: SRAM DUB road crank or SRAM DUB mountain crank spacer chart - Our cups w/seals add 2mm in overall width (1mm for each cup/side) compared to SRAM DUB BB cups, so subtract 1mm from each side of SRAM's spacer numbers - If SRAM calls for no (zero) outer/spindle spacers on the non-drive side (left), you may have to subtract 2mm from the drive side (right) to make things fit - Ex: SRAM calls for 3mm of spacer on the right and zero on the left, run 1mm on the right and zero on the left. - 24mm Shimano HollowTech II cranks - Our cups are the same width (each) as Shimano road BB cups - Our cups are 1mm wider (each) than Shimano mountain BB cups but are compatible with Shimano mountain cranks