I don't see how changing the BB can do anything more than move the problem around. When you get that 26 far enough out not to hit the big ring, the chainline for the big ring will be too cocked to reach most of the inside cogs. I'm not a big fan of the 16th tooth difference and this sounds like another disadvantage. My Ram has a 44/30. For gears below that I think a triple is a better choice. I run 48/34/26 on the Saluki, Trek,i & tandem, but think the 45/35/25 that RBW sells makes a lot of sense for those of us who need more help on the long, steep climbs.
Of course the cross chaining you are referring to is never a good idea. I would recommend avoiding it no matter what rings are on the bike. On my triple I would only use the middle ring with the 1 & 9 cogs very briefly, to avoid a front end shift. When riders select gear combinations they often focus on the range but it is also important to look at the shifting pattern. Ten & fourteen tooth differences usually yield simpler patterns than 12 & 16. For triples the 10 tooth difference makes finding the next gear much easier than a 16 tooth dbl., which offsets the added inconvenience of the triple. Michael On Sunday, August 2, 2015 at 11:25:05 PM UTC-4, RDS wrote: > > Rear spacing is 130 on the Soma San Marcos. I have tried a 110 BB and > currently a 118 BB. Same issue using both BB's. Again, this is just in > the workstand setting things up. Meaning, I have not rode the bike yet. > Installed the crank on a VO Campeur and the Soma San Marcos and same issue > on both. So, asking the question from ignorance as I am a novice mechanic > at best. Thanks for the feedback. > > On Saturday, August 1, 2015 at 8:43:14 PM UTC-4, Dave Johnston wrote: >> >> That is the cross-chain audible warning mode. It is a feature. >> >> What size BB are you using and is the rear spacing 130mm or 135mm. I have >> not experienced this on the 3 double setups I'm using. 43/29, 40/26, an >> 42/28 >> >> -Dave >> >> On Friday, July 31, 2015 at 2:53:00 AM UTC-4, RDS wrote: >>> >>> Installed the Sugino Wide/Low double Crank (40/26). Still in repair >>> stand. 9 Speed. Cassette is 11/34. When the chain is in the small ring >>> up front and the small ring in the back (yes, I realize that this might not >>> be a good gear combination to ride in), the chain is making contact with >>> the inside of the big ring. To clarify, the chain is NOT coming in contact >>> with the FD, but the inside portion of the big chain ring. >>> >>> Does this mean that I need a BB that is more wide? Or does this mean >>> that I should never have the chain in that combination? Or ??? Any help >>> appreciated. >>> >>> Bike is a 59 Soma San Marcos. >>> >> -- 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 http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
