Hi!

I have a Campagnolo nuovo record 70's era crank that I would convert with single chainring.
I would like to know what it will be the best option with bottom bracket to get the best chainline

FYI my frame is Colnago with italian thread

Thanks for your advise !

The best way to determine the answer is to mount every thing with your current bottom bracket, take measurements, and calculate how many mm you need to move your chain ring. Subtract (usually you will be moving your crank inward) this from your current spindle length to get a specification for a new spindle or cartridge bottom bracket. If you do not have a bottom bracket at this time, you can take a guess, buy a cheap (i.e don't invest a lot of money at this point) BB unit and hope that it works. If not, you can use it to do the calculation above to then buy the right length.

Good luck.

Thanks for helping.
I don't have bottom bracket at this time... Do you think I can buy a symetric miche BB ? Because I read a lot of threads about that and it seems that old crank need an offset on one side.

Lots of Campy BB info here. Maybe some of it will be of help.
Most of it is related to road doubles. But maybe you can extrapolate from there.


Campagnolo bottom bracket info

You get the center of the rear aligned ... You dont say what it is,

But that is the goal in the front.

Good info.

Keep in mind which position you are going to mount the chainring on: inside or outside to calc BB spindle length.

My FG runs the 48T ring on the inside position for a perfect chainline on the OEM double 68 SS120 BB, but my frameset and rear wheel are not the same as yours.

-Bandera

My rear wheel is a custom made mavic open pro on halo free / fixed 130mm hub.
But as I am a newbie in single speed I don't know a lot about chainline, exept the fact that it must be straight.

I would like to have my chainring on outer place for aestetics reason

This way I presume spindle lenght affect the chainline

The best way to do it would be to use a cyclocross guard in the outer position, and keep everything else the same, or use a track crank.

I've always had trouble running a single chainring on a crank designed for doubles. Tends to loosen up. YMMV.

Unless you file off the inner chainring lands, that will be your limiting factor to move the drive side inboard.
The option to use the inner ring position is probably a good one.
The quick method is to mount the crank and wheel without chain and using a straightedge such as a section of L extrusion, pass it along the chainrings back to see where you are and the best option.