Wednesday, January 07, 2009
So after footering around to try and find a way to get the chainline sorted, i looked up old friend 63xc. Matt chester may not be flavour of the month, but he describes very nicely how to measure chainline. You need vernier gauge and a good ruler. ideally mm measurements.
Taker vernier gauge and measure diameter of seat tube. Half it. This is A.
Measure distance from middle of tooth on chainring to edge of seat tube. This is B.
Add A and B.
Then with ruler measure distance from inside of drop out to middle of cog at rear. This is C.
When measuring, measure with all bolts/creaks tight as they would be riding.
If you are using a 135 hub spacing, then the number to note is half this, or 67.5mm. Adjust for hub width as required.
C+A+B should equal 67.5 or as close as dammit.
So as there is limited movement with a screw on rear cog laterally, you are down to adjusting the B number for chainline. If you use a tomicog or london fixie cog then you can alter both.