Singlespeed & Fixed Gear - I measured my chain line now?

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View Full Version : I measured my chain line now?

jfmckenna
06-11-04, 09:04 AM
I have a new road frame. The frame is aligned. The bb shell is 70.9mm. I measured the chain line in the rear, ((hub width/2) - gap to frame)). The chainline came to 41.1mm. So the rear cog is 41.1mm from the frame center line. Do they sell bb's based on chain line? I only seem to see them sold as spindle length. Is there a formula for back calculating in this method such that knowing the chain line I can get the bb spindal length. It will have to be a square taper spindle. Also how does one know if one has an Italian or English thread?

motion sickness
06-12-04, 05:43 PM
The easiest way to get good chainline is to use the specific bottom bracket recommended by the crank manufacturer. 41 or 42 seems to be standard chainline for a track crankset. I'm running a 111mm Campy road BB with my Miche track crankset and it's not a perfect match, so I just moved one of the 2mm spacer washers to the other side of the rear hub and dished the wheel ever so slightly to get things to line up. Not the most elegant solution, but the chainline is spot on. Of course, if you have a double sided hub and want to be able to flip it over to a different cog, you'll have to do something else.

Italian BB's are right-hand thread on both sides, English BB's have left-hand thread on the non-drive side (left) side. I think English BB width is 68mm, so it sounds like an Italian job.