On 10 Jan Adam asked: " I'm thinking about moving away from a triple to a double in order to get a lower Q."
One option is a 1980's Sugino AT (110/74mm BCD) set for a double, say 46-33, sicne 33T is the smallest 110mm BCD ring out there, e.g. TA Zephyr on Peter White's site. The AT was designed as a low Q triple. * I have achieved 152mm Q with a Tange 127 cartridge BB and 2mm drive side spacer for a total asymmetry of 6mm, very close to the D-3U Sugino recommended. The Outer ring FCL is 45mm and the Inner ring FCL is 37mm with a 43.5mm RCL. * Others on the I-Bob list have stated 147mm Q. The AT Inner 74mm BCD ring uses very very low posts cast in the spider & 5mm spacers instead of higher cast posts using no spacer. The Middle 110mm DCB ring protrudes further inward than the 74mm holes. Therefore, removing the 74mm Inner ring and spacers creates a double with the Inner ring chainbolt head being the limiting clearance to the chainstay. The double has a Q of about 145mm with a 46-36. The only problem with a 110mm double is the smallest 110BCD ring in 33T. However, with a 12-36 9 speed cassette, a 46-33 is 1 gear higher than a 46-30 for a No Load low gear (24.1gi vs 20.4gi with 584x38). EBay seems to have a decent supply of AT's, I bought 2 a year ago, a 1980 and 1984 one. So unless you need the very lowest No Load low, a Sugino AT as a double may work. John Hawrylak Woodstown NJ On Wednesday, January 10, 2024 at 11:15:06 AM UTC-5 Adam wrote: > Hi all, > > Adjacent to the triples thread, I'm thinking about moving away from a > triple to a double in order to get a lower Q. > > What are options for double cranksets that are around 40/26 or so? I think > that would be doable with the Rene Herse cranks, but too much $$$ for me. > Are there any cheaper options that will do that and give me a q in the 140s? > > Second, drivetrain stuff is a little new to me. What determines how small > a q factor a specific bike can have? I'm assuming chainstays play a role > here? This hypothetical project is for a Hillborne, so I'd be curious what > folks have used to get low q on their Hillbornes. I'm assuming I may have > to change the BB as well. > > Thanks! > > Adam > -- 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/74f36654-c145-4f29-bc31-e92e64241ffbn%40googlegroups.com.
