I need to replace the bottom bracket bearing on my fixie. I plan to get a Shimano UN26, but I note that there are a number of different sizes. The sizes seem to be expressed as 68-110, where 68 is the shell width and the second number varies according to the table below, from Shimano's tech specs.
I assume the second number relates to the width somehow.
How do I measure my existing bearing? Is it length from end to end of the axle? Given that the only tool I have for this is a ruler (no calipers) what's the best way of measuring my existing bottom bracket to ensure I get the right size?
I removed the bottom bracket and it had "103" stamped on the axle. I also measured and it was exactly 103mm from end to end. So it looks like the measure is the length. I went to my LBS and they assured me a 107mm (coincidently the shortest one they carried) would be fine. I installed it and my chainline is marginally out (I guess by 2mm). So I'm going to try to find a 103mm from somewhere else.