Road Bike Bottom Bracket Standards

For all shimano hollowtech ii road cranks double or triple standard or compact select all shimano cranks road button.

Road bike bottom bracket standards. The exact thread measurement is the same as road bikes 1 37 inches x 24 threads per inch. With the rise of carbon fibre as a frame material. The common threaded bottom bracket uses cups or adaptors with the thread specification of 1 37 x 24 threads per inch approximately 34 8mm diameter. Then measure both the inner diameter and width of your frame s bottom bracket shell.

Yet more bottom bracket standards. Both often require different bottom brackets even though spindle length and cup threading is the same. Confirm the crank standard of the crank set installed on your bike or the one you intend to install on your bike and select the appropriate replacement road bike bottom bracket above as follows. 68 or 73 mm.

68 mm is the most popular but 73 mm is catching on. Shimano was an early advocate of moving the bearings outside. Finding the correct bottom bracket for your frame can be challenging. Bearing seats were moulded into the carbon frame structure to save weight and bottom bracket shell width ballooned to 90mm on road bikes and 95mm on mountain bikes.

Threaded bottom brackets shells have been made over time in various thread standards that are not interchangeable. Instead of bearing pressed into aluminium cups that were then threaded into the frame trek pressed the bearings directly into the frame. To accurately determine the bottom bracket standard in your frame it is best that you remove your crankset and any installed bottom bracket cups or bearings.