The inside shelf is a weird Shimano lock-in thing and it can be easily filed off.
- Marc On Wednesday, October 21, 2020 at 8:41:58 AM UTC-7 Coal Bee Rye Anne wrote: > I'm curious whether anyone could confirm or deny if all 104/64bcd cranks > are created equal with middle/outer chainring compatibility or whether > there are possibly some variances in spider/shelf design? > > The reason I ask... and this is purely academic at this time as I've no > real need/time/expense to fully pursue any projects right now... is that I > just now became aware of a spec/design feature of my Deore LX FC-M571 > Octalink triple crank which actually has a different shelf height on the > middle and outer part of the 104bcd spider. > > I came to this realization after recently cleaning and mocking up my spare > crank for a potential 2021 build. I originally acquired this crank used as > a 22-32-44 triple on a hand me down frame plus parts and turned it into a > 32t bashguard sandwiched 1x crank for a while and then had picked up a > 64bcd 32t inner ring (see example in the link below) and temporarily set it > up as a 32t-32t-guard while experimenting with some chainline stuff on a > previous project. > > It never occurred to me before that 104bcd were unlike most 110bcd or > 130bcd cranks I have with matching shelf height/spacing on the inner(middle > if a triple)& outer ring positions. My line of thinking was that if the > 64bcd 32t position proved to offer better overall alignment than the middle > 104mm 32t position I could just shift the bashring to the middle position > with some single stack bolts. Plus it gives me the option of a future > 32-48t double for some more road oriented riding but I was rather > surprised to realize the chainguard and OEM outer 44t rings do not > actually fit the middle 104bcd position because there's shallower spacing > on the shelf to bolt hole on the inside and they'd need to be filed to fit. > > This realization had me further wondering about the 48t ring noted as > being compatible with my exact 64bcd 32t inner ring for a 2x double crank. > Anywhere I look I only find 48t SRAM/Truvativ rings spec'd as outers and/or > for triples with 104bcd (any 48t doubles I've found are a different BCD > altogether.) > > I'll admit my search hasn't been overly thorough, and possibly even more > confusing with the same ring often being labeled as 'SRAM in Truvativ > packaging' but for a 32t ring that everywhere I find it clearly states 'for > use with 48t' I've yet to find the complementary 48t 'for use with 32t' > that would specifically fit as a middle 104bcd. > > My moderate investment in this still useful 104/64bcd crank with spare > BB-ES51 bottom brackets for both 68mm and 73mm shells and Riv's recent > release of the 104/64bcd Silver crank is mostly what has me wondering... > > > https://planetcyclery.com/sram-32-tooth-64mm-bcd-aluminum-chainring-gray-use-with-48t?gclid=Cj0KCQjwuL_8BRCXARIsAGiC51Cx5-QnwJ5GwH4cASMAgEDJ8yy9wxwkgIGS-zdE3hVNrWIPDNsfh9caAvpcEALw_wcB > > You could certainly argue that if I'm ultimately after a narrower 1x > chainline and/or 32t/40something double for pavement usage I'd be better > off with a narrower q crank, and you'd generally be correct. I do also > have another option with a 110 crank and rings that should be sufficient > but just more or less trying to figure out the possibilities and details > I've apparently overlooked all these years on 104bcd. > > Thanks, > Brian Cole > Lawrenceville NJ > -- 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/160554c2-bb59-4f72-8828-cb01a1b0012an%40googlegroups.com.
