What Bottom Bracket Spindle length you need in order to achieve a particular chain line depends on what crankset you are running. Even if you know what crankset you are running, sometimes the results differ from the numbers you look up. In general, if you buy everything together, a well informed vendor can sell you the right stuff. For example, if you buy your frame-set and your crank set and your BB from Rivendell, they can probably sell you a combo that works. In general if you are trying to fit a second hand frame set with a random crank set, it's best pulled together by a mechanic who has several choices at their disposal. My BB box probably has close to 20 different things inside, so I can afford to iterate a little bit. For a home-mechanic with no inventory, maybe the BB choosing would be best hired out to the LBS. "Here's my frame and my cranks. Please sell me and install for me a BB that will give me 45mm chain line". Once it's done, now you know and you're good for a few years of riding.
Bill Lindsay El Cerrito, CA On Monday, September 8, 2025 at 2:08:19 AM UTC-7 [email protected] wrote: > Thanks Nick. I'm running a 9speed with a double up front. Do you have any > idea what BB spindle length I should be choosing? Sorry... I find all this > V confusing! > > On Sunday, 7 September 2025 at 07:12:55 UTC+1 Nick Payne wrote: > >> Depends slightly on what speed cassette you're using, but 45mm should be >> close to ideal. Or this Park Tool article explains how to calculate it >> yourself: >> https://www.parktool.com/en-int/blog/repair-help/chainline-concepts. >> >> Nick Payne >> > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/3ca99eae-80c0-4b66-b6b0-13a09ccfcf5fn%40googlegroups.com.
