which BB for a triple crankset
04-17-21, 09:09 AM
#1
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which BB for a triple crankset
I am building up a Rivendell Sam Hillborne, trying to use as many of my spare parts as possible.
Plan is to use a triple crankset.
and I have about ... 15 English threaded BB to choose from. ranging in axle width from 102mm to...102, 111, 112, 113, 114, 115. 117, 123 and even 129.5
so, how do I figure out which length axle BB should work with which crankset?
of course there is trial and error....
and trying a Shimano Biopace with a 123mm BB the small ring (28t) was touching the chainstay.
but, strangely trying a 114 BB with a Specialized crankset (small ring 24t).
i guess the smaller specialized 24t small ring would of course allow more space.
is there anyway of knowing "I have crankset X with small ring Yteeth" and so I will need a BB with Z axle width.
Plan is to use a triple crankset.
and I have about ... 15 English threaded BB to choose from. ranging in axle width from 102mm to...102, 111, 112, 113, 114, 115. 117, 123 and even 129.5
so, how do I figure out which length axle BB should work with which crankset?
of course there is trial and error....
and trying a Shimano Biopace with a 123mm BB the small ring (28t) was touching the chainstay.
but, strangely trying a 114 BB with a Specialized crankset (small ring 24t).
i guess the smaller specialized 24t small ring would of course allow more space.
is there anyway of knowing "I have crankset X with small ring Yteeth" and so I will need a BB with Z axle width.
04-17-21, 09:15 AM
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I see you have the bottom brackets taped and marked. A good way is to measure the bb and tape the crankset when they come off. Maybe someone has started an info thread in here to store those numbers?
04-17-21, 09:55 AM
#3
Really Old Senior Member
With all those sizes I've NEVER seen listed before, I'm suspect of your measuring technique. It's NOT the total length of the spindle, but at a a reference point where the "square" has specific dimensions.
Compare DS only between the different BB's to see which has the length to put the crank where it needs to be.
Sheldon has a database of BB lengths/crank. maybe your crank is included?
https://www.sheldonbrown.com/bbsize.html
Compare DS only between the different BB's to see which has the length to put the crank where it needs to be.
Sheldon has a database of BB lengths/crank. maybe your crank is included?
https://www.sheldonbrown.com/bbsize.html
04-17-21, 10:04 AM
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One tried and true method is to install the best guestimate then find out the small ring/stay clearance dimension and the chainline dimension. Then if needed remove and install the Bb that reflects the corrected dimensions. With so many BB's on hand...
Everything else being equal the usual amount of longer BB axle for when going from a double to a triple (with the same crank arm) is no more then 5mm extra on the drive side, often a bit less. But if a different crank arm is in play then following the manufacturer's guidelines (if any) or test fit/experiment as above. Andy
Everything else being equal the usual amount of longer BB axle for when going from a double to a triple (with the same crank arm) is no more then 5mm extra on the drive side, often a bit less. But if a different crank arm is in play then following the manufacturer's guidelines (if any) or test fit/experiment as above. Andy
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Last edited by Andrew R Stewart; 04-17-21 at 10:09 AM.
04-17-21, 10:33 AM
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at the time I was disassembling these various bikes, I didn't realize that BB and Crankset were so closely paired.
Nor did I realize that French stems had a different insert than.... normal stems.
nor did I know that handlebars had different clamp diameters.
Needless to say the last 10 years messing around with bikes - and going from complete Know Nothing to my present rank of Moderately Aware - has been eyeopening....
Had I only known then what I am learing now....
Nor did I realize that French stems had a different insert than.... normal stems.
nor did I know that handlebars had different clamp diameters.
Needless to say the last 10 years messing around with bikes - and going from complete Know Nothing to my present rank of Moderately Aware - has been eyeopening....
Had I only known then what I am learing now....
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04-17-21, 11:47 AM
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Whatever crank you use will determine the BB needed. Figure out which crank you plan on using and then use Sheldon Brown or VeloBase to look up the specs or check on the Shimano tech docs if using Shimano stuff and then get the correct bottom bracket. You may not have the correct BB in your parts bin and might have to buy a new one.
