My belt drive bicycle came with a Shimano internal bottom bracket. Shimano BB UN300, 127 mm length, 68 mm width, square taper. Below a picture. On the part is written
- BB UN300
- 68 UJ
- BC137x24D-EL
I bought a replacement. The body is 2mm longer. Below a picture of the replacement. The part number is EBBUN300KB27X And on the part is written
- BB UN300 K
- 68 VL
- BC137x24D-EL
The replacement's body is about 2mm longer. All other parts seem the same size / length. The axle length is 127mm on both.
I installed the replacement. There is no play / seems to sit well.
- Inside the frame: On the non drive side the bearings are 2mm further towards the outside of the frame (but still within the frame).
- Outside the frame: the cup cannot be turned in all the way. It sticks out 2mm. Although the cup is not flush against the frame, I assume the cup is sitting against the bearing.
Questions
- How "bad" are the 2mm?
- Can the frame get damaged?
- Will the life of the replacement be reduced?