Joe, this picture was incredibly helpful - once I saw it the Riv instructions made immediate sense. This method does result in a few more links than Sheldon's guideline would call for, but I don't see an immediate downside to being able to accommodate a slightly longer chain.
Jay Lonner Bellingham, WA On Sat, Feb 29, 2020 at 4:38 PM Joe Bernard <joerem...@gmail.com> wrote: > Here's a not particularly easy to see shot because it's indoors and > everything is black, but hopefully explains what Riv is saying. > > With the chain on the smallest front and rear cogs, the pulley cage is > sitting parallel to the bottom run of the chain. If the chain were much > longer it would lead to the rear of the cage kicking up until that bottom > run of chain was clanking into the pulleys themselves, and the chain would > dangle loosely in that gear. Basically you want your chain as long as you > can get it without that looseness/clanking happening. > > Yes the derailer up high looks weird, yes it works. It shifts the > small/middle rings as designed, and doesn't know that somebody replaced the > big ring with a chain guard approximately the same size as the middle ring. > How this came about is Grant/Riv originally conceived this crank setup to > run without a fd, you would just stop and move the chain by hand. This > didn't make it past whoever talked them out of it when bikes were built > with them 😬 > > On Saturday, February 29, 2020 at 4:07:56 PM UTC-8, Jay Lonner wrote: > > I'm making slow progress on a 55cm Cheviot build for my wife and am hung > up on determining the proper chain length. The Riv website says: > > > > > > >The chain is the right length when it pulls the derailer cage free of > > and parallel to the chain itself when wrapped around the smallest cog > > and the smallest chainring -- i.e., the derailer cage will be flexed > > slightly. > > > > > > Try as I might, I'm having a hard time visualizing what this means - can > anyone unpack this further for me? A picture would be even better! (The > there's also Sheldon's rule of thumb calling for one full link of overlap > when the chain is wound around the large-large chainring/sprocket combo, > but I'd still like to understand the Riv method). > > > > > > I'm also a a little stuck on front derailer options. I'm setting this up > with the Silver wide-low double (38x24 with chainguard) and the front > derailers I have on hand (IRD Alpina-f, Suntour XC-9000) both have a lot of > daylight between the bottom of the cage and the chainguard. It looks funny, > but would it affect performance? I'm open to buying a new part if needed, > but am getting a bit Marie Kondo and would rather declutter my parts stash > than add to it. > > > > > > Thanks, > > > > > > Jay Lonner > > Bellingham, WA > > -- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/rbw-owners-bunch/17efa4c6-55c4-4a5a-8cb2-aed42866dde8%40googlegroups.com > . > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/CAJnE%2B%3DcsULas1viU%3DU%2Bn%3DZmfqNPj70H5uO77%3DsAj9GGNRqtrKA%40mail.gmail.com.
