BB spindle length: It's always safe and usually best to use the bb the crank maker recommends, or (more to the point) a dimensional equivalent. I'm not going to address taper here, just quick notes about length. It comes down to chainline, which has nothing to do with the chain. Almost everything anybody could possibly say about CL has already been said by Sheldon on his site, but I don't remember whether he addressed derailers there, so I will fast here. Chainline is how far out from the center of the seat tube the middle ring on a triple sits, or the midpoint between two rings on a double sits.
There are two common chainlines, I mean three: 43 or 43.5mm (I forget)--for road doubles 47.5mm -- for road triples and hybrid-like bikes. 50.5 or 51(I forget) -- for mtn bikes "For" means "typical," not "the only way." But what it means is that mtn bike front derailers can reach farther out and can't drag in as close as road front derailers. Example: If you put a Sugino or Silver crank on a 110mm bb spindle, the chainline will be 47.5, and an XT or any other mtn front derailer will be able to shift to the big ring, but not to the small one. To fix that, you put a 113mm bb spindle, which changes the CL from 47.5 to 50.5, and it all works. There is no perfect correlation bwt Q-Factor and CL. In general, mtn cranks are for bow-legged cowboys and they have high Q's, but it's easy to design and make great mtn cranks with mtn bike CLs and low-Q's (under 163?). The mtn crank makers don't generally do that, though, because then their cranks won't fit onto lots of expensive and prestigious bikes that have chainstays that stick out too far in the wrong spots and so require higher Q-Factors. This doesn't address durability, but it's rare to hear of $40 bb's crapping out. Not unheard of, but it's not unheard of at any price, either. We are going to stock an ol' cup-and-cone style BB in ass't lengths sometime this year. It will cost more and we'll refuse to sell it to -- how do I best say this? -- a "newbie with romantic/retro sensibilities but no experience with this kind of BB." We certainly won't quit selling the $40 Shimano bbs, which are so good. What we will do, when it all happens, is extol the theoretical virtues of the old kind...which, given the reliabiliy of the new kind, are undeniable, but may not matter. G On Wednesday, April 27, 2016 at 1:27:49 PM UTC-7, dstein wrote: > > Why are more expensive bottom brackets more expensive? What do you gain? > Is it just durability? Or is there any sort of performance gain (ie, does > it roll smoother, faster, etc)? > > I've worked on most bike parts now minus the bottom bracket and headset. > About to change cranks on my hunqapillar form the Sugino triple (with a 107 > or 110 bb) to a White Industries Eno (with a 113 bb). Trying to figure out > if I go w/ the $40 bb on Riv's site? Or a White Industries or something > similar? This bike will see 500-1000 miles a year on dirt and some mud. And > support the occasional overnighter. > -- 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 rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at https://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
