Um frame too perhaps? Basically all it is is you want the straightest chain line possible, usually it means the shortest axle possible (unless your dropouts are 8ft apart as will says ) Im absolutly crap with bb lengths im afraid. Will Arnold says that his 118mm gigapipe JUST about clears the shell of a zoo python when using the old tensiles + an eno. You should be fine with a 118mm for the clearance side if you're using a cog. But for the love of gerald, don't quote me on that.....