Bottom Bracket Conundrum.
09-18-19, 12:31 PM
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Bottom Bracket Conundrum.
I have a Holdsworth Mistral and as it has rack mount bosses I believe it is a 1983, the only year they had them. (Please do correct me if im wrong)
I also have a Gipiemme Dual Sprint double crankset which I wish to fit to said Mistral.
So....it is ISO, and the arms are straight but I have no idea what length BB spindle I require and after much head scratching I thought I'd ask people who are almost guaranteed to know more than me. On One Cycles say thier 110mm will fit nearly all ISO but then say 113mm if you buy thier Holdsworth cranks!?
The BB in the frame is give or take a knats whisker 120mm but pretty confident its JIS and dont know what cranks were on it so no help.
I shall return to my trusty Surly LHT and await your collective brilliance.
Thanks for listening.
I also have a Gipiemme Dual Sprint double crankset which I wish to fit to said Mistral.
So....it is ISO, and the arms are straight but I have no idea what length BB spindle I require and after much head scratching I thought I'd ask people who are almost guaranteed to know more than me. On One Cycles say thier 110mm will fit nearly all ISO but then say 113mm if you buy thier Holdsworth cranks!?
The BB in the frame is give or take a knats whisker 120mm but pretty confident its JIS and dont know what cranks were on it so no help.
I shall return to my trusty Surly LHT and await your collective brilliance.
Thanks for listening.
09-18-19, 01:19 PM
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Get a 113, put it on and try it. How's the chainline? Too far out? Get a 110. (But first check to make sure you have 3mm+ of clearance between your closet chainring and chainstay.) Bike will be ridable until then. 3 mm off offends purists but will work.
BB, spindle length and cranksets are not an exact science. Even if all the parts are machined to fine tolerances. that changes once the (relatively soft aluminum) crank has been mounted and removed a few times. And fine tolerances and adherance to specifications was never a bike industry strong suit. Plus tapered spindles and cranksets are a place where very small differences in thickness make large differences in chainring placement.
Ben
BB, spindle length and cranksets are not an exact science. Even if all the parts are machined to fine tolerances. that changes once the (relatively soft aluminum) crank has been mounted and removed a few times. And fine tolerances and adherance to specifications was never a bike industry strong suit. Plus tapered spindles and cranksets are a place where very small differences in thickness make large differences in chainring placement.
Ben
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09-18-19, 01:32 PM
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09-19-19, 04:22 AM
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09-19-19, 04:47 AM
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I'd start with the 110 since the collective wisdom here indicates that's *most* likely to be ideal - and if that ends up being too short, it's still a useful size to have in your stash. Downside is that unlike starting with a 113, bike won't be rideable as you impatiently wait for UPS man to bring you the alternate size!
09-19-19, 05:06 AM
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Get a 113, put it on and try it. How's the chainline? Too far out? Get a 110. (But first check to make sure you have 3mm+ of clearance between your closet chainring and chainstay.) Bike will be ridable until then. 3 mm off offends purists but will work.
BB, spindle length and cranksets are not an exact science. Even if all the parts are machined to fine tolerances. that changes once the (relatively soft aluminum) crank has been mounted and removed a few times. And fine tolerances and adherance to specifications was never a bike industry strong suit. Plus tapered spindles and cranksets are a place where very small differences in thickness make large differences in chainring placement.
Ben
BB, spindle length and cranksets are not an exact science. Even if all the parts are machined to fine tolerances. that changes once the (relatively soft aluminum) crank has been mounted and removed a few times. And fine tolerances and adherance to specifications was never a bike industry strong suit. Plus tapered spindles and cranksets are a place where very small differences in thickness make large differences in chainring placement.
Ben
09-19-19, 06:41 AM
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In a quick visual reference of the crankset - it is of a time where they copied Campagnolo
so, 113 ayssemetrical- length offset toward drive side. Many cartridge bottom brackets are equal left and right. If using one of that type you may have to go wider- will end up with extra on the off drive side.
that could guide you to 118mm
so, 113 ayssemetrical- length offset toward drive side. Many cartridge bottom brackets are equal left and right. If using one of that type you may have to go wider- will end up with extra on the off drive side.
that could guide you to 118mm
09-19-19, 10:47 AM
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This is a really good question. So going from 70 to 68 and visa versa would you just add/subtract the 2mm from the distance of the middle of the BB spindle? That would keep the sides the same. Is that the way to do it? Here is Sheldon's database.
https://www.sheldonbrown.com/bbsize.html
https://www.sheldonbrown.com/bbsize.html
