I've been going through this with a Toyo Atlantis with curved chainstays, which "get wider sooner" (closer to the BB) than straight chainstays. That requires a wider BB/-spindle unless there is a straight section on the chainstays before the curve, as on my ~'84 StumpJumper.
I am also pretty convinced that, all else equal, a double requires a wider BB/-spindle than a triple because the smallest/innermost ring on the triple is smaller than that on the double, hence, it can fit it closer. You save Q factor (FWIW) with a double in that there are only 2 rings instead of the triple's 3. Stating the obvious JIC. This "innermost ring" effect is the same thing as the 1x issue of the bigger the ring, the wider out it needs to go. So, can that triple really not fit? If not, the solution to this problem is not a double; that will just require an even wider BB/-spindle. Note: VO and RH doubles can only go down to about 28t I think, which won't fit into a smaller hole than your 24t. And you can't just put a smaller inner ring on your triple. I guess 22t would be the smallest possible. I'm a little stumped and wish I could get my eyes and hands on it. But you could try a spacer on the drive side but it does put that side out wider. Another option: shave the bottom-inside of your crank arms to clear your chainstays. There is a Bicycle Quarterly article about this. Or find a double crankset that accommodates a tiny (24t or less) inner ring - white industries? - get as wide a BB/-spindle as you need, but your feet won't be as wide as with a triple. Is it possible you're threading in the drive side too far and the NDS not enough? There seems to be some "wiggle room" with BBs in this sense. There isn't an alignment for dead center. Group, is it ok to play with that? Is this not what a spacer does. Oh, and does 68 mm vs. 73 mm BB come into play here? Crank arm bow is new to me; makes sense; glad to pick that up in this thread. -Matthew P fiddling with the BB on the Toyo Atlantis for way too long, but intermittently. i'm really just lagging oddly its those curves that i like so much. all love requires work :) in San Diego, CA ( Kumeyaay ) On Monday, April 26, 2021 at 5:26:12 AM UTC-7 Garth wrote: > I also ran a AT triple with a UN72 127mm bb. I don't recall needing a > spacer as it was on my '83 Stumpjumper that had excellent ring clearance, > no bowed stays. It was perfectly centered. The tread width was still very > low compared to anything "modern". I still have it around so maybe later > I'll measure it uninstalled, a hand press as Ray did. In riding the extra > length spindle made no difference to me. In a blind test I would not be > able to tell a difference. Years later I'm riding a 170mm tread width > triple and even that makes no difference to me. > > On Sunday, April 25, 2021 at 7:59:14 PM UTC-4 Ray Varella wrote: > >> Joe, >> I just measured the Sugino AT on a 127mm spindle. I get 153mm without >> cinching the bolts down. This is just a hand press fit with a gentle tap to >> make sure they are on straight. >> Since you want a wide range double, I’m assuming you plan on using the >> inner ring. >> By eliminating the inner ring and running a compact double that would >> allow running a narrower Q >> >> I don’t think most modern cranks will improve on that for you. >> >> Hope that helps >> >> Ray >> >> On Sunday, April 25, 2021 at 4:18:43 PM UTC-7 Joe M. wrote: >> >>> Ok thanks for everyone's input this is helpful. I'll look into making >>> these work. >>> >>> But if anyone does have a wide range double they'd part with, I'd still >>> be interested in possibly purchasing it. >>> >>> On Sunday, April 25, 2021 at 4:09:55 PM UTC-7 Patrick Moore wrote: >>> >>>> Bob; It all comes down to arm flare. I got 160 mm Q with a Sugino XD2 >>>> and 113 mm spindle; I got a 160 mm Q with a TA Pro 5 Vis and a custom 145 >>>> mm spindle. >>>> >>>> On Sun, Apr 25, 2021 at 5:02 PM Bob Lovejoy <[email protected]> wrote: >>>> >>>>> I am not expert enough to explain where the differences come from, but >>>>> different cranks use different bb spindle lengths to get the same >>>>> configuration. The Sugino AT's just happen to use a relatively long >>>>> spindle but once installed they clear the chainstays exactly as they >>>>> should. That said, being a triple, the Q factor is going to be more than >>>>> a >>>>> double. >>>> >>>> -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/dd132562-55f9-47c4-9990-8a01c1d7a120n%40googlegroups.com.
