Hi guys, I’m looking for some help to workout what length BB i should run on my first fixie build. I have been slowly collecting parts including a free frame from Jolan (thanks mate - http://fixed.org.au/forums/index.php/topic,7764.0.html).
So my question is what BB axle length (square taper) should i run to get a straight chainline and not hit the cranks on the frame? Cranks are Galli (double ring) road cranks to be converted to single 44t 3/32" Campy chainring. Rear wheel is Campy track tubular with single sided fixed with 15t.
There are no hard and fast rules here that I’m aware of, it’s a matter of getting out the ruler (preferably calipers) and measuring.
The easiest way to know for sure is measure the front chainline with the current axle, and subtract 2mm of axle length for every 1mm of chainline you want to move in. This assumes the axle is symmetrical which is not always the case.
You may have to run the chainring on the inside depending on the clearance. Who knows, if you run it on the inside you might not need a new BB. By the way, swapping chainring sides alters the chainline by about 5-7mm.
Cheers for the info. Unfortunatley the frame didn’t come with a BB as a starting point. I can’t even pull out my daily ride BB as it uses Cotter Pins and my new cranks are square taper…
Most track cranks go onto a 108 spindle. I put road cranks on a 110 spindle and got a 42mm chainline with the chainring on the inside mounts. To get that chailine on the outsidemounts, I would have required a 102 spindle.
What is the chainline of the hub?
This is what I would do: take it to LBS, tell them you want a 4Xmm chainline (to match hub) and let them figure out which BB is right. If you buy one and it’s wrong, they might not let you swap if after it’s been installed.
This is one part of a build that in your particular situation you should take to a good LBS. If you tell em you want a straight chainline and drop it off they’ll have to do all the hard work and figure it out and you won’t be left with a bunch of BB’s that you have no use for. Either that or they may let you exchange them if the first one is wrong.
Yeah, I have three spare BB’s now from my latest build. Fortunately the shimano ones are pretty cheap. 20 -30 for un26 or un54s. I have a 103 and a 110 if you need either of those.
If you’re not a nuff nuff like myself you should be able to start with one (ie. 107mm) and then work out what you do need if its wrong.
If there is a way to work it out without doing a practice first I’d be interested to know. All depends on the various cranks, frame and rear spacing.