Bicycle Mechanics - Bottom Bracket spidle length for 54mm chainline
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02-23-10, 06:19 AM
I am building a Rohloff touring bike, and would like to buy only one bottom bracket :). Ill probably use an SKF bb, which comes in 113, 116, 121 lengths.
Ill likely use either a sugino AT crank that I have, or a new Sugino xd600 triple with the ring on the outside. maybe something else, if there is a reason...
just curious if anyone knows for sure which BB spindle length to use with either crankset.... I need a 54mm chainline.
As a side note, does anyone have any other crank suggestions without breaking the bank? I'm pretty sold on the roller bearings in the SKF bb unit, but am not sure about the cranks.
Thanks for the help!
02-23-10, 07:26 AM
I'm getting a proper road-triple chainline (~45mm as measured to the middle ring) using a Sugino XD600 with a 110mm bottom bracket. Keep in mind that the 110mm BB is asymmetrical, and has the same drive-side extension as a 107mm BB. (the extra 3mm on the non-drive-side is necessary to get the non-drive-side pedal equidistant from the frame's centerline).
Here's a thread that I started a few years ago about symmetry of standardized (sealed-cartridge) square-taper bottom brackets (http://www.bikeforums.net/showthread.php?196235-how-to-tell-if-bottom-brackets-are-symmetrical-(if-no-one-says-so)).
From my measurements I think you'd be fine with a 113mm bottom bracket.
According to Sheldon Brown's bottom-bracket size database, the Sugino AT takes a pretty wide bottom bracket spindle already. which would be a reason for going with the XD600.
02-23-10, 08:31 AM
thanks for the reply...
so youre saying that with your 107 (driveside) BB, you are getting 45mm chainline at the centre. if i went to 113 (driveside) BB, that should put me at 51mm centre ring?
what is the distance from centre ring to outer ring?
sorry for the questions, but for a 100$ BB, i dont want to do trial and error... :)
anybody else have any input?
02-23-10, 09:11 AM
Shimano UN-54 - $20 (http://www.nashbar.com/bikes/Product_10053_10052_194724_-1_201720_10000_201726).
When that fails (and the Shimano sealed units have reputation for holding up really well) you can get a $100 unit.
I seem to actually remember that 107mm is slightly asymmetrical in the reverse, with drive-side spindle being 1mm longer than NDS, while 110mm has NDS 2mm longer than drive-side.
When I compared a 113mm to a 110mm this morning, at my desk (pulled some extras out of a box) the 113 actually seemed comparable spacing to the 110mm, but slightly wider on both sides. Should have clarified this better in previous post.
I have no idea if the SKF bottom bracket follows the same spacing as Shimano units, but most JIS BB's made nowadays probably do. For it to be worth that price, maybe it should have adjustable chainline (like the Phil Wood units).
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