So I need to replace an RPM BB7420 but can’t find the same company (FSA?) part in Australia
When I measured the shell it came up as 68mm despite 73mm being written on the part. It does measure 73mm when I extend the caliper to the bit I’ve highlighted in blue.
Question- do I order a 73mm or a 68mm ?
And also does shimano do a part that fits? Spindle is 122.5. (Calliper isn’t out as it measured spindle correctly)
Thanks
by paddyb12341
3 Comments
You need to measure the shell of the frame. What you have measured is an arbitrary distance across the BB. You haven’t even taken the other side out.
It looks like you need a square taper BB for a 73 mm shell with a 122.5 spindle length. Shimano do the UN300 in a 123 mm length which will work for you
Measure the frame, not the BB
The bb shell of the frame is the cartridge size. 68, 73, or 70, (Italian). The spindle is measured from end to end. The crank determines what size is appropriate. 108 – 128 mm.