Originally Posted by
torean
zand, I'm looking for a sealed cartridge replacement, but thanks anyway
rothen, I'm more than certain that I need the iso/british 68mm BB, its the length that is confusing me. I was thinking since 130mm is the most common road hub, what bb length is everyone else using with a double?
also what variables would there be for a bike to use a 115mm length compared to a 117mm and vice versa.
I had the same questions about going from an asymmetrical spindle to a symmetrical cartridge. I was replacing an old touring bike triple with a 128mm spindle. It was 4mm longer on the drive side than the non-drive. That would be taking 2mm off the driveside and adding 2mm to the other side. Not much. I went with a 127.5 Shimano cartridge and it worked fine. The chainline is very proper. If you are going with a double crank, the length will be shorter. Image wanting the middle of the double crank, the distance inbetween the the chainrings lining up with the center cog of the freewheel. Try it with what you have if you can without tightening it down. Getting a proper chainline using math and measurements is possible. I just don't know how to do it. The difference between 115 and 117 is almost insignificant, 1mm to either side. The important thing is to not get a length so short that the inner ring rubs the chainstay.