Ted Thanks very much for the detailed explanation and 25mm of cable pull for the SunTour barcons
Did you measure the RD ratio's or are they a published value somewhere?? Do you happen to know the ratio for a Shimano Deore M-591-SGS?? I have this with a Shimano 9sp road cassette (4.34mm cog spacing). The RD ratio would have to greater than 1.39 for the SunTour barcon 25mm travel to shift the 8 cog spacings on the 9 speed cassette (8 * 4.34)/25 = 1.39 John Hawrylak Woodstown NJ On Tuesday, November 29, 2022 at 9:04:58 AM UTC-5 Ted Durant wrote: > On Sunday, November 27, 2022 at 8:43:17 PM UTC-6 Scott wrote: > >> Your research task: find out how much RD moves with each ratchet of your >> 1975s. Then you'll be able to better assess compatibility with different >> cassettes of any maker/speed, as long as you get the respective cog >> spacing. >> > > I spent an inordinate amount of time on this topic and put together a > spreadsheet (naturally). I found 25 clicks on my SunTour BarCons, and 25mm > of total cable pull, so each click is 1.0mm. > > Rear derailer ratio, the amount of horizontal movement per mm of cable > movement, varies pretty widely, from 1.1 (Shimano 11 mtn, SRAM 7-9 Mtn) (I > did this before 12 and 13 speed...) to 1.90 (SunTour). > > The SunTour BarCon has a pretty small barrel, and 25mm isn't enough cable > pull for a low-ratio derailer across a large number of cogs. For example, a > Shimano 11-speed MTB derailer needs 36mm of cable pull. > > If you want to dial it in, a Campy newer 9-speed derailer with a matching > cassette needs 3.03mm of cable pull (3 BarCon clicks) for each cog. Or, > combine a Shimano 10 or 11 speed derailer with a SunTour freewheel and > you'll use right around 2mm (2 clicks) per cog. > > There aren't many combo's that line up with even 1 mm clicks. > > Ted Durant > Milwaukee, WI USA > -- 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/f6b894e5-b845-4c37-9477-e716f5bf9832n%40googlegroups.com.
